A

21 files changed, 2344 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..5a65a47
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,92 @@
+# ---> C
+# Prerequisites
+*.d
+
+# Object files
+*.o
+*.ko
+*.obj
+*.elf
+
+# Linker output
+*.ilk
+*.map
+*.exp
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Libraries
+*.lib
+*.a
+*.la
+*.lo
+
+# Shared objects (inc. Windows DLLs)
+*.dll
+*.so
+*.so.*
+*.dylib
+
+# Executables
+*.exe
+*.out
+*.app
+*.i*86
+*.x86_64
+*.hex
+
+# Debug files
+*.dSYM/
+*.su
+*.idb
+*.pdb
+
+# Kernel Module Compile Results
+*.mod*
+*.cmd
+.tmp_versions/
+modules.order
+Module.symvers
+Mkfile.old
+dkms.conf
+
+# ---> C++
+# Prerequisites
+*.d
+
+# Compiled Object files
+*.slo
+*.lo
+*.o
+*.obj
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Compiled Dynamic libraries
+*.so
+*.dylib
+*.dll
+
+# Fortran module files
+*.mod
+*.smod
+
+# Compiled Static libraries
+*.lai
+*.la
+*.a
+*.lib
+
+# Executables
+*.exe
+*.out
+*.app
+
+.dccache
+
+client
+server
\ No newline at end of file
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..8820f85
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,33 @@
+
+.DELETE_ON_ERROR:
+
+CXX = g++
+SRCDIR := src
+INCLDIR = include
+BUILDDIR = build
+CFLAGS := -Wall -Wextra -g
+
+all: client server
+
+client: $(BUILDDIR)/client.o
+	$(CXX) $(CFLAGS) $(BUILDDIR)/client.o $(BUILDDIR)/util.o $(BUILDDIR)/comms.o -o client
+
+server: $(BUILDDIR)/server.o
+	$(CXX) $(CFLAGS) $(BUILDDIR)/server.o $(BUILDDIR)/util.o $(BUILDDIR)/comms.o -o server
+
+$(BUILDDIR)/client.o: $(SRCDIR)/client.cpp $(INCLDIR)/client.hpp $(BUILDDIR)/comms.o $(BUILDDIR)/util.o
+	$(CXX) $(CFLAGS) -I$(INCLDIR) $(SRCDIR)/client.cpp -c -o $(BUILDDIR)/client.o
+
+$(BUILDDIR)/server.o: $(SRCDIR)/server.cpp $(INCLDIR)/server.hpp $(BUILDDIR)/comms.o $(BUILDDIR)/util.o
+	$(CXX) $(CFLAGS) -I$(INCLDIR) $(SRCDIR)/server.cpp -c -o $(BUILDDIR)/server.o
+
+$(BUILDDIR)/comms.o: $(SRCDIR)/comms.cpp $(INCLDIR)/comms.hpp $(BUILDDIR)/util.o
+	$(CXX) $(CFLAGS) -I$(INCLDIR) $(SRCDIR)/comms.cpp -c -o $(BUILDDIR)/comms.o
+
+$(BUILDDIR)/util.o: $(SRCDIR)/util.cpp $(INCLDIR)/util.hpp
+	$(CXX) $(CFLAGS) -I$(INCLDIR) -c $(SRCDIR)/util.cpp -o $(BUILDDIR)/util.o	
+
+clean:
+	-rm client server $(BUILDDIR)/*.o 2> /dev/null || true
+
+.PHONY: all clean
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/README.md
diff --git a/build/.keep b/build/.keep
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/build/.keep
diff --git a/include/client.hpp b/include/client.hpp
new file mode 100644
index 0000000..dfc3e0c
--- /dev/null
+++ b/include/client.hpp
@@ -0,0 +1,17 @@
+#ifndef client_H
+#define client_H
+
+#include "comms.hpp"
+
+void RemoveConnection(int i);
+int Send_Blocking(int sockFD, const BYTE *data, int len);
+
+void DoClient(const char *svrIP, int svrPort, const char *fileName);
+
+void doClientCommand(int i);
+
+void prepareSend(int i, Header header);
+int processReception(int i);
+void printMessage(int i);
+
+#endif
diff --git a/include/comms.hpp b/include/comms.hpp
new file mode 100644
index 0000000..1b2a942
--- /dev/null
+++ b/include/comms.hpp
@@ -0,0 +1,32 @@
+#ifndef COMM_UTIL_H
+#define COMM_UTIL_H
+#include "util.hpp"
+
+struct CONN_STAT {
+  int id;          // Unique id to identify a client instance
+  bool isLoggedIn; // Used by server to identify that this connection is logged
+                   // in
+  struct timeb lastTime;  // Last time this connection was used (used to detect
+                          // s2c closure)
+  bool recInitHeader;     // False until initial header is recieved
+  bool expectingHeader;   // The message to be read is a header (irrelevent for
+                          // senders)
+  enum LinkType linkType; // MESSAGE_LINK (persistent) or FILE_LINK (one off)
+  enum Direction direction; // C2S or S2C
+  char name[9];             // The user this connection is with
+  int nBuffered;            // number of bytes in the buffer
+  int messageLen; // size of the current message being sent (includes header)
+  int nToDo; // num bytes to do before current messsage is completed (message
+             // len --> 0)
+  bool changeDirection; // Flag to change the direction of the connection once
+                        // the current communication finishes
+  bool shouldClose;          // Flag to destroy this connection
+};
+
+int Send_NonBlocking(int sockFD, BYTE *data, struct CONN_STAT *pStat,
+                     struct pollfd *pPeer);
+int Recv_NonBlocking(int sockFD, BYTE *data, struct CONN_STAT *pStat,
+                     struct pollfd *pPeer);
+void SetNonBlockIO(int fd);
+
+#endif
diff --git a/include/server.hpp b/include/server.hpp
new file mode 100644
index 0000000..ab77ad8
--- /dev/null
+++ b/include/server.hpp
@@ -0,0 +1,27 @@
+#ifndef server_H
+#define server_H
+
+// Comms includes util.hpp
+#include "comms.hpp"
+
+void SetNonBlockIO(int fd);
+void RemoveConnection(int i);
+
+int Send_NonBlocking(int sockFD, BYTE *data, struct CONN_STAT *pStat,
+                     struct pollfd *pPeer);
+int Recv_NonBlocking(int sockFD, BYTE *data, struct CONN_STAT *pStat,
+                     struct pollfd *pPeer);
+
+int processReception(int i);
+void doServerCommand(int i);
+void sendMessageToId(int id, bool reqLoggedIn, Header header, char *message);
+void sendMessageToAllLoggedIn(Header header, char *message);
+void sendMessageToAllLoggedInExceptSender(int senderID, Header header,
+                                          char *message);
+void sendMessageToName(char *name, Header header, char *message);
+void prepareMessage(int i, Header header, char *message);
+void printServerCommand(int i);
+
+void DoServer(int svrPort);
+
+#endif
diff --git a/include/util.hpp b/include/util.hpp
new file mode 100644
index 0000000..10887df
--- /dev/null
+++ b/include/util.hpp
@@ -0,0 +1,141 @@
+#ifndef UTIL_H
+#define UTIL_H
+
+// Get your libraries here
+#include <arpa/inet.h>
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <poll.h>
+#include <signal.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/timeb.h>
+#include <sys/wait.h>
+#include <time.h>
+#include <unistd.h>
+
+#define NAME "SERVER"
+#define ANON "Anonymous"
+#define LINE_SIZE 5000 // overkill
+
+#define BUF_LEN 12000000 // overkill
+#define MAX_REQUEST_SIZE 10000000
+#define MIN_USERNAME_LEN 4
+#define MAX_USERNAME_LEN 8
+#define MIN_PASSWORD_LEN 4
+#define MAX_PASSWORD_LEN 8
+
+enum Command {
+  REGISTER = 0, // [username] [password] Register a new account
+  LOGIN = 1,  // [username] [password] Log in with an existing account and enter
+              // the chat room
+  LOGOUT = 2, // Log out and leave the chat room
+  SEND = 3,   // [msg] Send a public message
+  SEND2 = 4,  // [username] [msg] Send a private message to a user
+  SENDA = 5,  // [msg] Send an anonymous public message
+  SENDA2 = 6, // [username] [msg] Send an anonymous private message to a user
+  SENDF = 7,  // [local file] Send a file publicly
+  SENDF2 = 8, // [username] [local file] Send a file to a user privately
+  LIST = 9,   // List all online users
+  DELAY = 10, // [N] A special command that delays for N seconds before
+              // executing the next command in the script
+
+  GETF = 11,    // [filename] Server telling clinet to request a file, clinet
+                // requesting a file
+  PING = 12,    // Check that connection is still there (nop)
+  CONNECT = 13, // [unique id] Allows the server to identify specific users when
+                // they are logged in multiple times
+
+  INVALID = 15 // Used when no valid command is found
+};
+
+enum LinkType { MESSAGE_LINK, FILE_LINK };
+
+typedef unsigned char BYTE;
+typedef unsigned int DWORD;
+typedef unsigned short WORD;
+
+enum Command parse_command(char *line);
+bool isValidUsername(char *username);
+bool isValidPassword(char *password);
+
+void Error(const char *format, ...);
+void Log(const char *format, ...);
+
+void buf2i(BYTE *buf, int &i);
+void i2buf(int &i, BYTE *buf);
+
+const char *com2str(enum Command command);
+
+double timeDifference(struct timeb a, struct timeb b);
+
+int getNumEntries(const char *databse);
+bool loginQuery(const char *database, char *username, char *password);
+bool usernameQuery(const char *database, char *username);
+
+void recordEntry(const char *database, char *key, char *value);
+void clearDatabase(const char *database);
+
+int buf2file(BYTE *buf, int nbytes, char *filename);
+int file2buf(char *filename, BYTE *buf);
+
+#define HEADER_LEN 13 // number of bytes in a message header
+
+enum Direction { C2S, S2C };  // client to server, server to client
+enum Flag { SUCCESS, FAIL };  // success, failure
+enum Recipient { PUB, PRIV }; // send to all, send to one
+enum Trace { SIGN, ANNON };   // send publically, send anonymously
+
+class Header {
+public:
+  enum Direction m_direction;
+  enum Flag m_flag;
+  enum Recipient m_recipient;
+  enum Trace m_trace;
+  enum Command m_command;
+
+  BYTE m_name[9];
+
+  int m_size;
+
+  Header(); // constructor
+
+  void encode(BYTE *buf); // encode message to buffer
+  void decode(BYTE *buf); // decode buffer to message
+
+  void setFlags(enum Direction direction, enum Flag flag,
+                enum Recipient recipient, enum Trace trace);
+
+  void displayContents(bool tab); // helper to print contents of class
+};
+
+inline bool operator==(const Header &lfs, const Header &rhs) {
+  bool result = true;
+
+  result &= lfs.m_direction == rhs.m_direction;
+  result &= lfs.m_flag == rhs.m_flag;
+  result &= lfs.m_recipient == rhs.m_recipient;
+  result &= lfs.m_trace == rhs.m_trace;
+  result &= lfs.m_command == rhs.m_command;
+
+  for (int i = 0; i < MAX_USERNAME_LEN; i++)
+    result &= lfs.m_name[i] == rhs.m_name[i];
+
+  result &= lfs.m_size == rhs.m_size;
+
+  return result;
+}
+
+inline bool operator!=(const Header &lhs, const Header &rhs) {
+  return !(lhs == rhs);
+}
+
+#endif
diff --git a/src/client.cpp b/src/client.cpp
new file mode 100644
index 0000000..baf2215
--- /dev/null
+++ b/src/client.cpp
@@ -0,0 +1,591 @@
+#include "client.hpp"
+
+// Connection 0: Client to Server data communication
+#define C2S_DATA 0
+// Connection 1: Server to Client data communication
+#define S2C_DATA 1
+// Other: Temporary file transer
+
+#define C2S_SERVICE_FREQ 1.0 // seconds
+#define MAX_CONCURRENCY_LIMIT 1000
+#define POLL_TIMEOUT 333 // poll timeout in ms
+
+int nConns; // number of active connections
+struct pollfd
+    peers[MAX_CONCURRENCY_LIMIT + 1]; // sockets to be monitored by poll()
+struct CONN_STAT
+    connStat[MAX_CONCURRENCY_LIMIT + 1]; // app-layer stats of the sockets
+BYTE *buf[MAX_CONCURRENCY_LIMIT + 1];
+
+struct sockaddr_in serverAddr;
+int id;
+
+// Duplicate exists in server and client
+void RemoveConnection(int i) {
+  close(peers[i].fd);
+  if (i < nConns) {
+    memmove(peers + i, peers + i + 1, (nConns - i) * sizeof(struct pollfd));
+    memmove(connStat + i, connStat + i + 1,
+            (nConns - i) * sizeof(struct CONN_STAT));
+    free(buf[i]);
+    memmove(buf + i, buf + i + 1, (nConns - i) * sizeof(BYTE *));
+  }
+  nConns--;
+  // Log("[%s] %d active connections after removal", SERVER_NAME, nConns);
+}
+
+int Send_Blocking(int sockFD, const BYTE *data, int len) {
+  int nSent = 0;
+  while (nSent < len) {
+    int n = send(sockFD, data + nSent, len - nSent, 0);
+    if (n >= 0) {
+      nSent += n;
+    } else if (n < 0 && (errno == ECONNRESET || errno == EPIPE)) {
+      Log("Connection closed.");
+      close(sockFD);
+      return -1;
+    } else {
+      Error("Unexpected error %d: %s.", errno, strerror(errno));
+    }
+  }
+  return 0;
+}
+
+void DoClient(const char *svrIP, int svrPort, const char *fileName) {
+  memset(&serverAddr, 0, sizeof(serverAddr));
+  serverAddr.sin_family = AF_INET;
+  serverAddr.sin_port = htons((unsigned short)svrPort);
+  inet_pton(AF_INET, svrIP, &serverAddr.sin_addr);
+
+  // ignore the SIGPIPE signal that may crash the program in some corner cases
+  signal(SIGPIPE, SIG_IGN);
+
+  // Creating unique identifier for this instance
+  // id = (int)(seconds since 1970) ^ (((int)(process id) & 0x0000FFFF) << 16)
+  struct timeb currentTime;
+  ftime(&currentTime);
+  id = currentTime.time ^ (((int)getpid() & 0x0000FFFF) << 16);
+  // Log("My identifier is %d (%08X)", id, id);
+
+  // create the data communication sockets
+  for (int i = 0; i < 2; i++) {
+    int fd = socket(AF_INET, SOCK_STREAM, 0);
+    if (fd == -1)
+      Error("Cannot create initial sockets.");
+
+    if (connect(fd, (const struct sockaddr *)&serverAddr, sizeof(serverAddr)) !=
+        0) {
+      Error("C2s cannot connect to server %s:%d.", svrIP, svrPort);
+    }
+
+    enum Direction direction;
+    if (i == C2S_DATA) {
+      direction = C2S;
+    } else {
+      direction = S2C;
+    }
+
+    // Notify the server this instance exists
+    BYTE connectBuf[20] = {0};
+    Header header;
+    header.setFlags(direction, SUCCESS, PUB, SIGN);
+    header.m_command = CONNECT;
+    memcpy(header.m_name, "--------", MAX_USERNAME_LEN);
+    header.m_size = 4;
+    header.encode(connectBuf);
+    i2buf(id, connectBuf + HEADER_LEN);
+    // header.displayContents(true);
+
+    if (Send_Blocking(fd, connectBuf, HEADER_LEN + header.m_size) < 0) {
+      Error("Cannot send CONNECT for connection %d", i);
+    }
+
+    SetNonBlockIO(fd); // TODO: Put this in somewhere
+
+    nConns++;
+    peers[i].fd = fd;
+    peers[i].revents = 0;
+
+    buf[i] = (BYTE *)malloc(BUF_LEN);
+
+    memset(&connStat[i], 0, sizeof(struct CONN_STAT));
+    ftime(&connStat[i].lastTime);
+    connStat[i].direction = direction;
+    connStat[i].linkType = MESSAGE_LINK;
+    connStat[i].nBuffered = 0;
+    connStat[i].messageLen = 0;
+
+    if (i == S2C_DATA) {
+      // Log("S2C_DATA is setting POLLRDNORM");
+      connStat[i].expectingHeader = true;
+      connStat[i].nToDo = HEADER_LEN;
+      peers[i].events |= POLLRDNORM; // S2C reads
+    }
+  }
+
+  // Client begins executing commands from the file.
+  FILE *fp = fopen(fileName, "r");
+  if (!fp)
+    Error("Failed to open the file: %s", fileName);
+
+  char *new_line_pos; // Remove '\n' from end of lines
+  char line[LINE_SIZE] = {0};
+  char disposableLine[LINE_SIZE] = {0};
+  char loginName[MAX_USERNAME_LEN + 1] = {0};
+  struct timeb
+      wakeUpTime; // if current time > wakeUpTime, get a line from the file
+  int flag, fd;
+  bool endOfFile = false;
+
+  // Wait a second for server to instanciate both connections.
+  // Sometimes responses aren't sent since the s2c connection hasn't
+  // finished connecting before the c2s connection sends a message.
+  sleep(1);
+
+  while (1) {
+    ftime(&currentTime);
+
+    double timeDiff = timeDifference(currentTime, wakeUpTime);
+    if ((timeDiff > 0) && (!endOfFile)) {
+      if (fgets(line, LINE_SIZE, fp) == NULL) {
+        Log("End of command file.");
+        endOfFile = true;
+        goto DO_POLL;
+      }
+
+      new_line_pos = strchr(line, '\n');
+      if (new_line_pos != NULL)
+        *new_line_pos = 0;
+
+      // TODO: Parse the command here, append messages to buffers as necessary
+      strncpy(disposableLine, line, LINE_SIZE);
+      enum Command command = parse_command(disposableLine);
+      strncpy(disposableLine, line, LINE_SIZE);
+      Header header;
+      char *tok, *rest;
+      int offset, nbytes, filenameLen = 0;
+      BYTE *stagingBuf = (BYTE *)malloc(BUF_LEN);
+
+      switch (command) {
+      case DELAY:
+        wakeUpTime = currentTime;
+        wakeUpTime.time += atoi(&line[6]);
+        break;
+      case REGISTER:
+        header.setFlags(C2S, SUCCESS, PUB, SIGN);
+        header.m_command = REGISTER;
+        tok = strtok(disposableLine, " "); // REGISTER
+        tok = strtok(NULL, " ");           // [username]
+        memcpy(header.m_name, tok, strlen(tok));
+        tok = strtok(NULL, " "); // [password]
+        header.m_size = strlen(tok);
+        header.encode(&buf[C2S_DATA][connStat[C2S_DATA].nBuffered]);
+        memcpy(&buf[C2S_DATA][connStat[C2S_DATA].nBuffered + HEADER_LEN], tok,
+               strlen(tok));
+        prepareSend(C2S_DATA, header);
+        break;
+      case LOGIN:
+        header.setFlags(C2S, SUCCESS, PUB, SIGN);
+        header.m_command = LOGIN;
+        tok = strtok(disposableLine, " "); // LOGIN
+        tok = strtok(NULL, " ");           // [username]
+        memcpy(header.m_name, tok, strlen(tok));
+        tok = strtok(NULL, " "); // [password]
+        header.m_size = strlen(tok);
+        header.encode(&buf[C2S_DATA][connStat[C2S_DATA].nBuffered]);
+        memcpy(&buf[C2S_DATA][connStat[C2S_DATA].nBuffered + HEADER_LEN], tok,
+               strlen(tok));
+        prepareSend(C2S_DATA, header);
+        break;
+      case LOGOUT:
+        header.setFlags(C2S, SUCCESS, PUB, SIGN);
+        header.m_command = LOGOUT;
+        memcpy(header.m_name, "-logout-", 8);
+        header.m_size = 0;
+        header.encode(&buf[C2S_DATA][connStat[C2S_DATA].nBuffered]);
+        prepareSend(C2S_DATA, header);
+        break;
+      case LIST:
+        header.setFlags(C2S, SUCCESS, PUB, SIGN);
+        header.m_command = LIST;
+        memcpy(header.m_name, "--list--", 8);
+        header.m_size = 0;
+        header.encode(&buf[C2S_DATA][connStat[C2S_DATA].nBuffered]);
+        prepareSend(C2S_DATA, header);
+        break;
+      case SEND:
+      case SENDA:
+        header.setFlags(C2S, SUCCESS, PUB, SIGN); // Will update trace as needed
+        if (command == SEND)
+          header.m_trace = SIGN;
+        else
+          header.m_trace = ANNON;
+        header.m_command = command;
+        memcpy(header.m_name, "--send--", 8);
+        tok = strtok_r(disposableLine, " ", &rest); // SEND[A]
+        header.m_size = strlen(rest); // Everything after 'SEND[A] '
+        header.encode(&buf[C2S_DATA][connStat[C2S_DATA].nBuffered]);
+        memcpy(&buf[C2S_DATA][connStat[C2S_DATA].nBuffered + HEADER_LEN], rest,
+               header.m_size);
+        prepareSend(C2S_DATA, header);
+        break;
+      case SEND2:
+      case SENDA2:
+        header.setFlags(C2S, SUCCESS, PUB, SIGN); // Will update trace as needed
+        if (command == SEND2)
+          header.m_trace = SIGN;
+        else
+          header.m_trace = ANNON;
+        header.m_command = command;
+        tok = strtok_r(disposableLine, " ", &rest); // SEND2[A]
+        tok = strtok_r(rest, " ", &rest);           // [username]
+        memcpy(header.m_name, tok, strlen(tok));
+        header.m_size = strlen(rest); // Everything after 'SEND2[A] [username] '
+        header.encode(&buf[C2S_DATA][connStat[C2S_DATA].nBuffered]);
+        memcpy(&buf[C2S_DATA][connStat[C2S_DATA].nBuffered + HEADER_LEN], rest,
+               header.m_size);
+        prepareSend(C2S_DATA, header);
+        break;
+      case SENDF:
+      case SENDF2:
+        header.setFlags(C2S, SUCCESS, PUB, SIGN); // Will update trace as needed
+        header.m_command = command;
+        if (command == SENDF) {
+          header.m_recipient = PUB;
+          memcpy(header.m_name, "--senf--", 8);
+          tok = strtok(disposableLine, " "); // SENDF
+          tok = strtok(NULL, " ");           // [file name]
+        } else {                             // SENDF2
+          header.m_recipient = PRIV;
+          tok = strtok(disposableLine, " "); // SENDF2
+          tok = strtok(NULL, " ");           // [username]
+          memcpy(header.m_name, tok, strlen(tok));
+          tok = strtok(NULL, " "); // [file name]
+        }
+
+        offset = 0;
+        i2buf(id, &stagingBuf[offset]); //  stagingBuf skips header
+        offset += 4;                    // unique id
+        filenameLen = strlen(tok);
+        i2buf(filenameLen, &stagingBuf[offset]);
+        offset += 4; // int length of file name
+
+        memcpy(&stagingBuf[offset], tok, strlen(tok));
+        offset += strlen(tok); // file name
+
+        nbytes = file2buf(tok, &stagingBuf[offset + 4]);
+        if (nbytes == -1)
+          break;
+        i2buf(nbytes, &stagingBuf[offset]);
+        offset += 4;      // file size int
+        offset += nbytes; // file length (offest now tells how many bytes to
+                          // copy into buf)
+
+        header.m_size = offset;
+        // Make a new connection
+        if (nConns >= MAX_CONCURRENCY_LIMIT) {
+          Log("Cannot perform file transfer. Maximum concurency reached.");
+        } else {
+          fd = socket(AF_INET, SOCK_STREAM, 0);
+          if (fd == -1) {
+            Log("Cannot create new socket.");
+          } else if (connect(fd, (const struct sockaddr *)&serverAddr,
+                             sizeof(serverAddr)) != 0) {
+            Log("Cannot connect to server for file transfer");
+          } else {
+            if (command == SENDF)
+              Log("[%s] Sending %s to everyone currently logged in.",
+                  NAME, tok);
+            else
+              Log("[%s] Sending %s to %s.", NAME, tok, header.m_name);
+
+            SetNonBlockIO(fd);
+            nConns++;
+            peers[nConns - 1].fd = fd;
+            peers[nConns - 1].revents = 0;
+
+            buf[nConns - 1] = (BYTE *)malloc(BUF_LEN);
+            header.encode(buf[nConns - 1]);
+            memcpy(&buf[nConns - 1][HEADER_LEN], stagingBuf, header.m_size);
+
+            memset(&connStat[nConns - 1], 0, sizeof(struct CONN_STAT));
+            ftime(&connStat[nConns - 1].lastTime);
+            connStat[nConns - 1].direction = C2S;
+            connStat[nConns - 1].linkType = FILE_LINK;
+            // TODO: Kill the connection??
+            prepareSend(nConns - 1, header);
+          }
+        }
+        break;
+      default:
+        Log("Cannot execute %s command: %s", com2str(command), line);
+      }
+      free(stagingBuf);
+    }
+
+  DO_POLL:
+    int nReady = poll(peers, nConns, POLL_TIMEOUT);
+    // Log("nReady %d", nReady);
+
+    if (nConns == 0) {
+      Log("[%s] The server has gone offline.", NAME);
+      return;
+    }
+
+    for (int i = 0; i < nConns; i++) {
+      // Handle reading data (s2c)
+      if (peers[i].revents & (POLLRDNORM | POLLERR | POLLHUP)) {
+        // Log("Recieving nonblocking!");
+        if (connStat[i].direction == S2C) {
+          if (Recv_NonBlocking(peers[i].fd, buf[i], &connStat[i], &peers[i]) <
+              0) {
+            // Log("Line %d: Removing connection %d", __LINE__, i);
+            RemoveConnection(i);
+            goto NEXT_CONNECTION;
+          }
+
+          if (connStat[i].nToDo == 0) {
+            if (processReception(i) != 0) {
+              // Log("Line %d: Removing connection %d", __LINE__, i);
+              RemoveConnection(i);
+            }
+            goto NEXT_CONNECTION;
+          }
+        }
+      }
+
+      // Handle sending data (c2s)
+      if (peers[i].revents & (POLLWRNORM | POLLERR | POLLHUP)) {
+        // Log("Sending nonblocking!");
+        if (connStat[i].direction == C2S) {
+          if (Send_NonBlocking(peers[i].fd, buf[i], &connStat[i], &peers[i]) <
+              0) {
+            // Log("Line %d: Removing connection %d", __LINE__, i);
+            RemoveConnection(i);
+            goto NEXT_CONNECTION;
+          }
+        }
+      }
+
+      // Check that the C2S connection is still open by sending a PING packet
+      if ((connStat[i].direction == C2S) &&
+          (timeDifference(currentTime, connStat[i].lastTime) >
+           C2S_SERVICE_FREQ) &&
+          (connStat[i].nToDo == 0) && (connStat[i].messageLen == 0) &&
+          (connStat[i].nBuffered == 0)) {
+        // Log("[%s] Pinging server on connection %d due to timeout",
+        // SERVER_NAME, i);
+        Header header;
+        header.setFlags(C2S, SUCCESS, PRIV, SIGN);
+        memcpy(header.m_name, "-client-", MAX_USERNAME_LEN);
+        header.m_command = PING;
+        header.m_size = 0;
+
+        header.encode(&buf[i][connStat[i].messageLen]);
+        connStat[i].nBuffered = HEADER_LEN + header.m_size;
+        connStat[i].messageLen = HEADER_LEN + header.m_size;
+        connStat[i].nToDo = HEADER_LEN + header.m_size;
+
+        peers[i].events |= POLLWRNORM;
+      }
+
+    NEXT_CONNECTION:
+      asm("nop");
+    }
+  }
+
+  // TODO: Close all open sockets
+  fclose(fp);
+}
+
+void prepareSend(int i, Header header) {
+  if (connStat[i].nBuffered == 0) {
+    connStat[i].messageLen = HEADER_LEN + header.m_size;
+    connStat[i].nToDo = HEADER_LEN + header.m_size;
+  }
+  connStat[i].nBuffered += HEADER_LEN + header.m_size;
+  peers[i].events |= POLLWRNORM;
+}
+
+int processReception(int i) {
+  Header header;
+  header.decode(buf[i]);
+
+  if (connStat[i]
+          .expectingHeader) { // Expecting a header read sequence was completed
+    // Log("\nProcessing header reception.");
+    // header.displayContents(true);
+    if (header.m_size > 0) {
+      connStat[i].expectingHeader = false;
+      connStat[i].nToDo = header.m_size;
+    } else if (header.m_size == 0) {
+      // printMessage(i);
+      doClientCommand(i);
+      connStat[i].expectingHeader = true;
+      connStat[i].nBuffered = 0;
+      connStat[i].nToDo = HEADER_LEN;
+      memset(buf[i], 0, BUF_LEN);
+    } else {
+      return -1; // Error, signal to caller to end connection
+    }
+  } else { // expecting a data read sequence was completed
+    // Log("\nProcessing data reception.");
+    // printMessage(i);
+    doClientCommand(i);
+    connStat[i].expectingHeader = true;
+    connStat[i].nBuffered = 0;
+    connStat[i].nToDo = HEADER_LEN;
+    memset(buf[i], 0, BUF_LEN);
+  }
+
+  if (connStat[i].shouldClose) {
+    // Log("[%s] Line %d: Removing connection %d due to shouldClose", SERVER_NAME,
+    // __LINE__, i);
+    RemoveConnection(i);
+  }
+
+  return 0;
+}
+
+void doClientCommand(int i) {
+  Header header;
+  header.decode(buf[i]);
+
+  int file_id;
+  int fd;
+  int offset;
+  char filename[5000];
+  int filenameLen, fileLen;
+
+  switch (header.m_command) {
+  case REGISTER:
+  case LOGIN:
+  case LOGOUT:
+  case LIST:
+    Log("[%s] %s", header.m_name, &buf[i][HEADER_LEN]);
+    break;
+  case SEND:
+  case SENDA:
+    Log("[%s] %s", header.m_name, &buf[i][HEADER_LEN]);
+    break;
+  case SEND2:
+  case SENDA2:
+    Log("<%s> %s", header.m_name, &buf[i][HEADER_LEN]);
+    break;
+  case SENDF:
+  case SENDF2:
+    // "[person] File transfer: <file name>"
+    // First 4 bytes are file id
+    buf2i(&buf[i][HEADER_LEN], file_id);
+    if (header.m_command == SENDF)
+      Log("[%s] Initiating file transfer: %s", header.m_name,
+          &buf[i][HEADER_LEN + 4]);
+    else
+      Log("<%s> Initiating file transfer: %s", header.m_name,
+          &buf[i][HEADER_LEN + 4]);
+    // Open new S2C connection with server for file transfer
+    fd = socket(AF_INET, SOCK_STREAM, 0);
+    if (fd == -1)
+      Log("[%s] Warning: Cannot create file transfer socket.", NAME);
+    else if (connect(fd, (const struct sockaddr *)&serverAddr,
+                     sizeof(serverAddr)) != 0)
+      Log("[%s] Warning: File transfer cannot connect to server", NAME);
+    else {
+      // Usual setup
+      SetNonBlockIO(fd);
+
+      if (nConns < MAX_CONCURRENCY_LIMIT) {
+        nConns++;
+        peers[nConns - 1].fd = fd;
+        peers[nConns - 1].revents = 0;
+
+        buf[nConns - 1] = (BYTE *)malloc(BUF_LEN);
+
+        memset(&connStat[nConns - 1], 0, sizeof(struct CONN_STAT));
+        ftime(&connStat[nConns - 1].lastTime);
+        connStat[nConns - 1].direction =
+            C2S; // will flip on completion of this send
+        connStat[nConns - 1].linkType = FILE_LINK;
+        connStat[nConns - 1].changeDirection = true;
+
+        Header outHeader;
+        outHeader.setFlags(S2C, SUCCESS, PUB,
+                           SIGN); // S2C used by server to set direction
+        if (header.m_command == SENDF2)
+          outHeader.m_recipient = PRIV;
+        outHeader.m_command = GETF;
+        memcpy(outHeader.m_name, header.m_name,
+               MAX_USERNAME_LEN); // pass along the name of the original sender
+        outHeader.m_size =
+            4 + header.m_size; // [client id] [file id] [file name]
+        outHeader.encode(buf[nConns - 1]);
+        offset = HEADER_LEN;
+        i2buf(id, buf[nConns - 1] + offset); // encode client id
+        offset += 4;
+        memcpy(&buf[nConns - 1][offset], &buf[i][HEADER_LEN],
+               header.m_size); // encode file id and file name
+        offset += header.m_size;
+
+        prepareSend(nConns - 1, outHeader);
+      } else
+        Log("[%s] Error: Cannot perform file transfer. Max concurrency "
+            "reached.",
+            NAME);
+    }
+    break;
+  case GETF:
+    if (header.m_flag == SUCCESS) {
+      buf2i(&buf[i][HEADER_LEN], filenameLen);
+      memcpy(filename, &buf[i][HEADER_LEN + 4], filenameLen);
+      buf2i(&buf[i][HEADER_LEN + 4 + filenameLen], fileLen);
+      buf2file(&buf[i][HEADER_LEN + 4 + filenameLen + 4], fileLen, filename);
+      if (header.m_recipient == PUB)
+        Log("[%s] File transfer complete: %s", header.m_name, filename);
+      else
+        Log("<%s> File transfer complete: %s", header.m_name, filename);
+    } else {
+      if (header.m_recipient == PUB)
+        Log("[%s] File transfer failed.", header.m_name);
+      else
+        Log("<%s> File transfer failed.", header.m_name);
+    }
+    connStat[i].shouldClose = true;
+    break;
+  case PING:
+    // Log("Ping from %s", header.m_name);
+    asm("nop"); // do nothing
+    break;
+  default:
+    Log("[%s] No doClientCommand() for %s", NAME,
+        com2str(header.m_command));
+  }
+}
+
+void printMessage(int i) {
+  Header h;
+  h.decode(buf[i]);
+
+  Log("[%s, %s, %s, %s] [%s]  [%s]  [%d]", !h.m_direction ? "C2S" : "S2C",
+      !h.m_flag ? "SUCCESS" : "FAIL", !h.m_recipient ? "PUB" : "PRIV",
+      !h.m_trace ? "SIGN" : "ANNON", com2str(h.m_command), h.m_name, h.m_size);
+
+  if (h.m_size > 0)
+    Log("\tData: [%s]", buf[i] + HEADER_LEN);
+}
+
+int main(int argc, char **argv) {
+
+  if (argc != 4) {
+    Log("Usage: %s [server IP] [server Port] [command script name]", argv[0]);
+    return -1;
+  }
+
+  const char *serverIP = argv[1];
+  int port = atoi(argv[2]);
+  const char *fileName = argv[3];
+
+  srand(time(NULL));
+
+  DoClient(serverIP, port, fileName);
+  return 0;
+}
diff --git a/src/comms.cpp b/src/comms.cpp
new file mode 100644
index 0000000..14fcd61
--- /dev/null
+++ b/src/comms.cpp
@@ -0,0 +1,169 @@
+#include "comms.hpp"
+
+int Send_NonBlocking(int sockFD, BYTE *data, struct CONN_STAT *pStat,
+                     struct pollfd *pPeer) {
+  while (pStat->nToDo > 0) {
+    // pStat keeps tracks of how many bytes have been sent, allowing us to
+    // "resume" when a previously non-writable socket becomes writable.
+    ftime(&(pStat->lastTime));
+    int n =
+        send(sockFD, data + pStat->messageLen - pStat->nToDo, pStat->nToDo, 0);
+    // Log("Send_NonBlocking n: %d", n);
+    if (n >= 0) {
+      pStat->nToDo -= n;
+    } else if (n < 0 && (errno == ECONNRESET || errno == EPIPE)) {
+      // Log("Connection closed.");
+      close(sockFD);
+      return -1;
+    } else if (n < 0 && (errno == EWOULDBLOCK)) {
+      // The socket becomes non-writable. Exit now to prevent blocking.
+      // OS will notify us when we can write
+      // Log("Writing would block. Waiting for OS to notify send.");
+      pPeer->events |= POLLWRNORM;
+      return 0;
+    } else {
+      Error("Unexpected send error %d: %s", errno, strerror(errno));
+    }
+  }
+
+  // Log("Message was completely written out (messagelen was message written
+  // out)"); Log("What's currently in there: nBuffered %d, messageLen: %d, nToDo
+  // %d", pStat->nBuffered, pStat->messageLen, pStat->nToDo);
+  memcpy(data, data + pStat->messageLen, BUF_LEN - pStat->messageLen); // Good
+  memset(data + pStat->nBuffered - pStat->messageLen, 0,
+         BUF_LEN - pStat->nBuffered + pStat->messageLen);
+  pStat->nBuffered -= pStat->messageLen;
+  if (pStat->nBuffered > 0) { // start off the next send if one is queued
+    Header nextHeader;
+    nextHeader.decode(data);
+    // Log("Another message is queued of size 13 + %d", nextHeader.m_size);
+    pStat->messageLen = HEADER_LEN + nextHeader.m_size;
+    pStat->nToDo = HEADER_LEN + nextHeader.m_size;
+  } else {
+    // Log("No other messages are queued");
+    pStat->messageLen = 0;
+    pStat->nToDo = 0;
+    pPeer->events &= ~POLLWRNORM; // no more bytes to send? Stop listening for
+                                  // the writable cue.
+  }
+  // Log("What's in there now: nBuffered %d, messageLen: %d, nToDo %d",
+  // pStat->nBuffered, pStat->messageLen, pStat->nToDo);
+
+  // Change the connection from a sender to a reciever (used by client)
+  if (pStat->changeDirection && (pStat->nToDo == 0)) {
+    // Log("Changing direction!: nBuffered: %d", pStat->nBuffered);
+    pStat->direction = (pStat->direction == C2S) ? S2C : C2S;
+    pStat->expectingHeader = true;
+    pStat->nToDo = HEADER_LEN;
+    pStat->changeDirection = false;
+    pPeer->events &= ~POLLWRNORM; // stop listening for writable cue
+    pPeer->events |= POLLRDNORM;  // start listening for readable cue
+  }
+
+  return 0;
+}
+
+// TODO: Question: Why isn't the pPeer datastructure used?
+int Recv_NonBlocking(int sockFD, BYTE *data, struct CONN_STAT *pStat,
+                     struct pollfd *pPeer) {
+  // pStat keeps tracks of how many bytes have been rcvd, allowing us to
+  // "resume" when a previously non-readable socket becomes readable. Log("Recv:
+  // pStat->nToDo %d",pStat->nToDo);
+  while (pStat->nToDo > 0) {
+    int n = recv(sockFD, data + pStat->nBuffered, pStat->nToDo, 0);
+    // Log("Rev_NonBlocking recieved %d bytes", n);
+    if (n > 0) {
+      pStat->nBuffered += n;
+      pStat->nToDo -= n;
+    } else if (n == 0 || (n < 0 && errno == ECONNRESET)) {
+      // Log("\nConnection closed. n = %d", n);
+      close(sockFD);
+      return -1;
+    } else if (n < 0 && (errno == EWOULDBLOCK)) {
+      // Log("\nWould block waiting for read...");
+      // The socket becomes non-readable. Exit now to prevent blocking.
+      // OS will notify us when we can read
+      return 0;
+    } else {
+      Error("Unexpected recv error %d: %s.", errno, strerror(errno));
+    }
+  }
+
+  return 0;
+}
+
+void SetNonBlockIO(int fd) {
+  int val = fcntl(fd, F_GETFL, 0);
+  if (fcntl(fd, F_SETFL, val | O_NONBLOCK) != 0) {
+    Error("Cannot set nonblocking I/O.");
+  }
+}
+
+Header::Header() {
+  m_direction = C2S;
+  m_flag = SUCCESS;
+  m_recipient = PUB;
+  m_trace = SIGN;
+  m_command = INVALID;
+  memset(m_name, 0, MAX_USERNAME_LEN + 1);
+  m_size = 0;
+}
+
+// encode the message to the buffer
+void Header::encode(BYTE *buf) {
+  memset(buf, 0, HEADER_LEN);
+  int index = 0;
+
+  BYTE dir_b = (BYTE)(m_direction << 7);
+  BYTE flag_b = (BYTE)(m_flag << 6);
+  BYTE recip_b = (BYTE)(m_recipient << 5);
+  BYTE trace_b = (BYTE)(m_trace << 4);
+  BYTE com_b = (BYTE)m_command & 0x0F;
+
+  buf[index++] = dir_b | flag_b | recip_b | trace_b | com_b;
+
+  memcpy(&buf[index], m_name, 8);
+  index += 8;
+
+  // NOTE: There was a problem encoding very large sizes.
+  i2buf(m_size, &buf[index]);
+  index += 4;
+}
+
+// decode a buffer into a message object
+void Header::decode(BYTE *buf) {
+  int index = 0;
+
+  m_direction = (enum Direction)((buf[index] >> 7) & 0x01);
+  m_flag = (enum Flag)((buf[index] >> 6) & 0x01);
+  m_recipient = (enum Recipient)((buf[index] >> 5) & 0x01);
+  m_trace = (enum Trace)((buf[index] >> 4) & 0x01);
+  m_command = (enum Command)(buf[index] & 0x0F);
+  index += 1;
+
+  for (int x = 0; x < MAX_USERNAME_LEN; x++)
+    m_name[x] = buf[index++];
+
+  buf2i(&buf[index], m_size);
+  index += 4;
+}
+
+void Header::setFlags(enum Direction direction, enum Flag flag,
+                      enum Recipient recipient, enum Trace trace) {
+  m_direction = direction;
+  m_flag = flag;
+  m_recipient = recipient;
+  m_trace = trace;
+}
+
+// Helper to print contents of class
+void Header::displayContents(bool tab = false) {
+  Log("%sDirection: %s,  Flag: %s,  Recipient: %s,  Trace: %s", tab ? "\t" : "",
+      !m_direction ? "C2S" : "S2C", !m_flag ? "SUCCESS" : "FAIL",
+      !m_recipient ? "PUB" : "PRIV", !m_trace ? "SIGN" : "ANNON");
+  Log("%sCommand: %s", tab ? "\t" : "", com2str(m_command));
+  char name[9] = {0};
+  memcpy(name, m_name, MAX_USERNAME_LEN);
+  Log("%sUsername: |%s|", tab ? "\t" : "", name);
+  Log("%sSize: %d", tab ? "\t" : "", m_size);
+}
diff --git a/src/server.cpp b/src/server.cpp
new file mode 100644
index 0000000..270a350
--- /dev/null
+++ b/src/server.cpp
@@ -0,0 +1,796 @@
+#include "server.hpp"	

+

+#define MAX_CONCURRENCY_LIMIT 40000 // overkill

+#define POLL_TIMEOUT 1000           // Milliseconds

+#define S2C_SERVICE_FREQ 1.0        // Seconds

+#define USER_DATABASE "user_database.txt"

+#define FILE_DATABASE "file_database.txt"

+#define FILES_DIR "files"

+

+int nConns; // total # of data sockets

+struct pollfd

+    peers[MAX_CONCURRENCY_LIMIT + 1]; // sockets to be monitored by poll()

+struct CONN_STAT

+    connStat[MAX_CONCURRENCY_LIMIT + 1]; // app-layer stats of the sockets

+BYTE *buf[MAX_CONCURRENCY_LIMIT + 1];

+

+// Duplicate exists in server and client

+void RemoveConnection(int i) {

+  close(peers[i].fd);

+  if (i < nConns) {

+    memmove(peers + i, peers + i + 1, (nConns - i) * sizeof(struct pollfd));

+    memmove(connStat + i, connStat + i + 1,

+            (nConns - i) * sizeof(struct CONN_STAT));

+    free(buf[i]);

+    memmove(buf + i, buf + i + 1, (nConns - i) * sizeof(BYTE *));

+  }

+  nConns--;

+  Log("[%s] %d active connections after removal", NAME, nConns);

+}

+

+void DoServer(int svrPort) {

+  int maxConcurrency = 20; // TODO: Change this to be a #define

+  int listenFD = socket(AF_INET, SOCK_STREAM, 0);

+  if (listenFD < 0) {

+    Error("[%s] Cannot create listening socket.", NAME);

+  }

+  SetNonBlockIO(listenFD);

+

+  struct sockaddr_in serverAddr;

+  memset(&serverAddr, 0, sizeof(struct sockaddr_in));

+  serverAddr.sin_family = AF_INET;

+  serverAddr.sin_port = htons((unsigned short)svrPort);

+  serverAddr.sin_addr.s_addr = htonl(INADDR_ANY);

+

+  int optval = 1;

+  int r =

+      setsockopt(listenFD, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));

+  if (r != 0) {

+    Error("[%s] Cannot enable SO_REUSEADDR option.", NAME);

+  }

+

+  signal(SIGPIPE, SIG_IGN);

+

+  if (bind(listenFD, (struct sockaddr *)&serverAddr, sizeof(serverAddr)) != 0) {

+    Error("[%s] Cannot bind to port %d.", NAME, svrPort);

+  }

+

+  if (listen(listenFD, 16) != 0) {

+    Error("[%s] Cannot listen to port %d.", NAME, svrPort);

+  }

+

+  nConns = 0;

+  memset(peers, 0, sizeof(peers));

+  peers[0].fd = listenFD;

+  peers[0].events = POLLRDNORM;

+  memset(connStat, 0, sizeof(connStat));

+

+  int connID = 0;

+  while (1) {

+    // monitor the listening sock and data socks, nConn+1 in total

+    int nReady = poll(peers, nConns + 1, POLL_TIMEOUT);

+    if (nReady < 0) {

+      Error("[%s] Invalid poll() return value.", NAME);

+    }

+

+    struct sockaddr_in clientAddr;

+    socklen_t clientAddrLen = sizeof(clientAddr);

+

+    struct timeb currentTime;

+    ftime(&currentTime);

+

+    // new incoming connection

+    if ((peers[0].revents & POLLRDNORM) && (nConns < maxConcurrency)) {

+      int fd = accept(listenFD, (struct sockaddr *)&clientAddr, &clientAddrLen);

+      if (fd != -1) {

+        SetNonBlockIO(fd);

+        nConns++;

+        Log("[%s] Accepted connection %d", NAME, nConns);

+        peers[nConns].fd = fd;

+        peers[nConns].events = POLLRDNORM;

+        peers[nConns].revents = 0;

+

+        memset(&connStat[nConns], 0, sizeof(struct CONN_STAT));

+        ftime(&connStat[nConns].lastTime);

+        connStat[nConns].recInitHeader =

+            false; // waiting to recieve initial header

+        connStat[nConns].expectingHeader =

+            true; // message to be read is a header

+        connStat[nConns].nToDo = HEADER_LEN;

+

+        buf[nConns] = (BYTE *)malloc(BUF_LEN);

+        memset(buf[nConns], 0, BUF_LEN);

+      }

+

+      if (--nReady <= 0)

+        continue;

+    }

+

+    for (int i = 1; i <= nConns; i++) {

+      // Log("nConns: %d peers[%d].revents: %02X (POLLRDNORM %02X, POLLWRNORM

+      // %02X, POLLERR %02X, POLLHUP %02X)", nConns, i, peers[i].revents,

+      // POLLRDNORM, POLLWRNORM, POLLERR, POLLHUP);

+      double timeDiff =

+          (currentTime.time + currentTime.millitm / (double)1000.0f) -

+          (connStat[i].lastTime.time +

+           connStat[i].lastTime.millitm / (double)1000.0f);

+

+      if (peers[i].revents &

+          (POLLRDNORM | POLLERR |

+           POLLHUP)) { // TODO: break out POLLERR and POLLHUP?

+        // Log("Servicing connection %d, POLLHUP: %d", i, peers[i].revents &

+        // POLLHUP);

+        //  Process initial communication

+        if (connStat[i].recInitHeader == false) {

+          if (Recv_NonBlocking(peers[i].fd, buf[i], &connStat[i], &peers[i]) <

+              0) {

+            Log("[%s] Line %d: Removing connection %d", NAME, __LINE__,

+                i);

+            RemoveConnection(i);

+            goto NEXT_CONNECTION;

+          }

+

+          if (connStat[i].nToDo == 0) {

+            Header header;

+            header.decode(buf[i]);

+            // Log("Initial communication for connection %d:", i);

+

+            if (!((header.m_command == CONNECT) | (header.m_command == SENDF) |

+                  (header.m_command == SENDF2) | (header.m_command == GETF))) {

+              Log("[%s] WARNING: Unexpected initial connection command %s",

+                  NAME, com2str(header.m_command));

+            }

+

+            connStat[i].recInitHeader = true;

+            connStat[i].expectingHeader =

+                true; // flag needed for processing below

+            if (processReception(i) != 0) {

+              Log("[%s] Line %d: Removing connection %d", NAME, __LINE__,

+                  i);

+              RemoveConnection(i);

+              goto NEXT_CONNECTION;

+            }

+          }

+        }      // End initial communication

+        else { // Standard polling recieve

+          // Log("Standard polling recieve/send: connStat[i].direction: %02X",

+          // connStat[i].direction);

+          if (connStat[i].direction == C2S) {

+            if (Recv_NonBlocking(peers[i].fd, buf[i], &connStat[i], &peers[i]) <

+                0) {

+              Log("[%s] Line %d: Removing connection %d", NAME, __LINE__,

+                  i);

+              RemoveConnection(i);

+              goto NEXT_CONNECTION;

+            }

+

+            if (connStat[i].nToDo == 0) {

+              if (processReception(i) != 0) {

+                Log("[%s] Line %d: Removing connection %d", NAME,

+                    __LINE__, i);

+                RemoveConnection(i);

+                goto NEXT_CONNECTION;

+              }

+            }

+          } // end C2S

+        }   // End standard recieve

+      }     // if POLLRDNORM

+

+      // a data socket is writable

+      if (peers[i].revents & POLLWRNORM) {

+        // Log("Sending nonblocking!");

+        if (Send_NonBlocking(peers[i].fd, buf[i], &connStat[i], &peers[i]) <

+            0) {

+          Log("[%s] Line %d: Removing connection %d", NAME, __LINE__, i);

+          RemoveConnection(i);

+          goto NEXT_CONNECTION;

+        }

+      }

+

+      // a s2c connection hasn't been used in a while? Check that the client is

+      // still there with a ping

+      if ((connStat[i].direction == S2C) && (timeDiff > S2C_SERVICE_FREQ) &&

+          (connStat[i].nToDo == 0) && (connStat[i].messageLen == 0) &&

+          (connStat[i].nBuffered == 0)) {

+        // Log("[%s] Pinging [%s] on connection %d due to timeout", SERVER_NAME,

+        // connStat[i].name, i);

+        Header header;

+        header.setFlags(S2C, SUCCESS, PRIV, SIGN);

+        memcpy(header.m_name, NAME, MAX_USERNAME_LEN);

+        header.m_command = PING;

+        header.m_size = 0;

+

+        header.encode(&buf[i][connStat[i].messageLen]);

+        connStat[i].nBuffered = HEADER_LEN + header.m_size;

+        connStat[i].messageLen = HEADER_LEN + header.m_size;

+        connStat[i].nToDo = HEADER_LEN + header.m_size;

+

+        peers[i].events |= POLLWRNORM;

+      }

+

+    NEXT_CONNECTION:

+      asm("nop");

+      // if (--nReady <= 0) break;

+    } // for

+  }   // while

+} // do_server

+

+// buf has all buffers

+// Stat has all stat structs

+// i is the index of the link being processed

+int processReception(int i) {

+  Header header;

+  header.decode(buf[i]);

+  // header.displayContents(true);

+

+  if (connStat[i]

+          .expectingHeader) { // Expecting a header read sequence was completed

+    // Log("\nProcessing header reception. header.m_size: %d", header.m_size);

+    if (header.m_size > 0) {

+      connStat[i].expectingHeader = false;

+      connStat[i].nToDo = header.m_size;

+    } else if (header.m_size == 0) {

+      // printServerCommand(i);

+      doServerCommand(i);

+      connStat[i].expectingHeader = true;

+      connStat[i].nBuffered = 0;

+      connStat[i].nToDo = HEADER_LEN;

+      memset(buf[i], 0, BUF_LEN);

+    } else {

+      return -1; // Error, signal to caller to end connection

+    }

+  } else { // expecting a data read sequence was completed

+    // Log("\nProcessing data reception.");

+    // printServerCommand(i);

+    doServerCommand(i);

+    if (connStat[i].direction == C2S) { // CONNECT events for S2C can get here

+      connStat[i].expectingHeader = true;

+      connStat[i].nBuffered = 0;

+      connStat[i].nToDo = HEADER_LEN;

+      memset(buf[i], 0, BUF_LEN);

+    }

+  }

+

+  if (connStat[i].shouldClose) {

+    Log("[%s] Line %d: Removing connection %d due to shouldClose", NAME,

+        __LINE__, i);

+    RemoveConnection(i);

+  }

+

+  return 0;

+}

+

+void doServerCommand(int i) {

+  // Assume the buf[i] has a message at the beginning of the buffers

+  Header header;

+  header.decode(buf[i]);

+

+  struct timeb currentTime;

+  ftime(&currentTime);

+

+  char message[5000] = {0};

+  char username[20] = {0};

+  char password[20] = {0};

+  Header outHeader;

+  int numLoggedIn = 0;

+  bool foundActiveUser = false;

+  int s2cConnNumb = -1;

+  char server_filename[5000] = {0};

+  char filename[5000] = {0};

+  int filenameLen, fileLen, offset, nextFileId, fileId;

+  BYTE intbuf[5] = {0};

+  FILE *fp;

+

+  switch (header.m_command) {

+  case CONNECT:

+    buf2i(&buf[i][HEADER_LEN], connStat[i].id);

+    connStat[i].direction = header.m_direction;

+    connStat[i].linkType = MESSAGE_LINK;

+    connStat[i].lastTime = currentTime;

+    if (header.m_direction == C2S) {

+      Log("[---- : %s] id: %d, direction: C2S, connection number: %d.",

+          com2str(header.m_command), connStat[i].id, i);

+      connStat[i].expectingHeader = true;

+      connStat[i].nBuffered = 0;

+      connStat[i].nToDo = HEADER_LEN;

+    } else {

+      Log("[---- : %s] id: %d, direction: S2C, connection number: %d.",

+          com2str(header.m_command), connStat[i].id, i);

+      connStat[i].nBuffered = 0;

+      connStat[i].messageLen = 0;

+      connStat[i].nToDo = 0;

+      peers[i].events &= ~POLLRDNORM;

+      peers[i].events &= ~POLLWRNORM;

+    }

+    memset(buf[i], 0, BUF_LEN);

+    break;

+  case REGISTER:

+    memcpy(username, header.m_name, MAX_USERNAME_LEN);

+    memcpy(password, &buf[i][HEADER_LEN], header.m_size);

+    if (usernameQuery(USER_DATABASE, username) == true) {

+      Log("[---- : %s] Registration failed. Username [%s] is already "

+          "registered.",

+          com2str(header.m_command), username);

+      outHeader.setFlags(S2C, FAIL, PUB, SIGN);

+      outHeader.m_command = REGISTER;

+      memcpy(outHeader.m_name, NAME, strlen(NAME));

+      strcat(message, "Cannot register username [");

+      strcat(message, username);

+      strcat(message, "]. Username already registered.\n");

+      strcat(message,

+             "\tUsernames may only contain characters a-z, A-Z, or 0-9.\n");

+      strcat(message, "\tUsernames may be 4 to 8 characters long.");

+      outHeader.m_size = strlen(message);

+      sendMessageToId(connStat[i].id, false, outHeader, message);

+    } else {

+      Log("[---- : %s] Successful registration (usr, pswd): %s  %s",

+          com2str(header.m_command), username, password);

+      recordEntry(USER_DATABASE, username, password);

+      outHeader.setFlags(S2C, SUCCESS, PUB, SIGN);

+      outHeader.m_command = REGISTER;

+      memcpy(outHeader.m_name, NAME, strlen(NAME));

+      strcat(message, "Successfully registered ");

+      strcat(message, username);

+      strcat(message, ".");

+      outHeader.m_size = strlen(message);

+      sendMessageToId(connStat[i].id, false, outHeader, message);

+    }

+    break;

+  case LOGIN:

+    memcpy(username, header.m_name, MAX_USERNAME_LEN);

+    memcpy(password, &buf[i][HEADER_LEN], header.m_size);

+    if (loginQuery(USER_DATABASE, username, password) == true) {

+      // Check that user is not currently logged in

+      for (int x = 1; x <= nConns; x++) {

+        if ((connStat[x].isLoggedIn == true) &&

+            (strcmp(username, connStat[x].name) == 0)) {

+          Log("[%s : %s] Login failed. User is already logged in.",

+              header.m_name, com2str(header.m_command));

+          foundActiveUser = true;

+          outHeader.setFlags(S2C, FAIL, PUB, SIGN);

+          outHeader.m_command = LOGIN;

+          memcpy(outHeader.m_name, NAME, strlen(NAME));

+          strcat(message, "Login failed. ");

+          strcat(message, username);

+          strcat(message, " is logged in on another device.");

+          outHeader.m_size = strlen(message);

+          sendMessageToId(connStat[i].id, false, outHeader, message);

+          break;

+        }

+      }

+

+      if (!foundActiveUser) {

+        for (int x = 1; x <= nConns; x++) {

+          if (connStat[i].id == connStat[x].id) {

+            memcpy(connStat[x].name, username, MAX_USERNAME_LEN);

+            // Log("Connection %d (%s) is loggin in.", x, connStat[x].name);

+            connStat[x].isLoggedIn = true;

+          }

+        }

+        Log("[%s : %s] Successful login (usr, pswd): %s  %s", connStat[i].name,

+            com2str(header.m_command), username, password);

+        outHeader.setFlags(S2C, SUCCESS, PUB, SIGN);

+        outHeader.m_command = LOGIN;

+        memcpy(outHeader.m_name, NAME, strlen(NAME));

+        strcat(message, "Welcome ");

+        strcat(message, username);

+        strcat(message, ".");

+        outHeader.m_size = strlen(message);

+        sendMessageToId(connStat[i].id, true, outHeader, message);

+      }

+    } else {

+      Log("[---- : %s] Login failed (usr, pswd): %s  %s",

+          com2str(header.m_command), username, password);

+      outHeader.setFlags(S2C, FAIL, PUB, SIGN);

+      outHeader.m_command = LOGIN;

+      memcpy(outHeader.m_name, NAME, strlen(NAME));

+      strcat(message, "Login failed: Invalid username or password.");

+      outHeader.m_size = strlen(message);

+      sendMessageToId(connStat[i].id, false, outHeader, message);

+    }

+    break;

+  case LOGOUT:

+    if (connStat[i].isLoggedIn) {

+      for (int x = 1; x <= nConns; x++) {

+        if (connStat[i].id == connStat[x].id) {

+          // Log("Connection %d (user %s) is logging off.", x,

+          // connStat[x].name);

+          connStat[x].isLoggedIn = false;

+          foundActiveUser = true;

+        }

+      }

+      Log("[%s : %s] Successful logout.", connStat[i].name,

+          com2str(header.m_command));

+      outHeader.setFlags(S2C, SUCCESS, PUB, SIGN);

+      outHeader.m_command = LOGOUT;

+      memcpy(outHeader.m_name, NAME, strlen(NAME));

+      strcat(message, "Goodbye ");

+      strcat(message, connStat[i].name);

+      strcat(message, ". Come back soon.");

+      outHeader.m_size = strlen(message);

+      sendMessageToId(connStat[i].id, false, outHeader, message);

+    } else {

+      Log("[---- : %s] Failed: Connection %d is not logged in.",

+          com2str(header.m_command), i);

+      outHeader.setFlags(S2C, FAIL, PUB, SIGN);

+      outHeader.m_command = LOGOUT;

+      memcpy(outHeader.m_name, NAME, strlen(NAME));

+      strcat(message, "Logout failed. You are not logged in.");

+      outHeader.m_size = strlen(message);

+      sendMessageToId(connStat[i].id, false, outHeader, message);

+    }

+    break;

+  case SEND:

+  case SENDA:

+  case SEND2:

+  case SENDA2:

+    if (connStat[i].isLoggedIn) {

+      outHeader.setFlags(S2C, SUCCESS, PUB, header.m_trace);

+      outHeader.m_command = header.m_command;

+      if (header.m_trace == SIGN)

+        memcpy(outHeader.m_name, connStat[i].name, strlen(connStat[i].name));

+      else

+        memcpy(outHeader.m_name, ANON, strlen(ANON));

+      memcpy(message, &buf[i][HEADER_LEN], header.m_size);

+      outHeader.m_size = strlen(message);

+      if ((header.m_command == SEND) || (header.m_command == SENDA)) {

+        Log("[%s : %s] %s", connStat[i].name, com2str(header.m_command),

+            message);

+        sendMessageToAllLoggedIn(outHeader, message);

+      } else {

+        memcpy(username, header.m_name, MAX_USERNAME_LEN);

+        Log("[%s : %s %s] %s", connStat[i].name, com2str(header.m_command),

+            username, message);

+        sendMessageToName(username, outHeader, message);

+      }

+    } else {

+      Log("[%s : %s] Failed: Connection %d is not logged in.", connStat[i].name,

+          com2str(header.m_command), i);

+      outHeader.setFlags(S2C, FAIL, PUB, SIGN);

+      outHeader.m_command = header.m_command;

+      memcpy(outHeader.m_name, NAME, strlen(NAME));

+      strcat(message, "Users must be logged in to '");

+      strcat(message, com2str(header.m_command));

+      strcat(message, "'. Login with '");

+      strcat(message, com2str(LOGIN));

+      strcat(message, " [username] [password]'.");

+      outHeader.m_size = strlen(message);

+      sendMessageToId(connStat[i].id, false, outHeader, message);

+    }

+    break;

+  case SENDF:  // Initial connection

+  case SENDF2: // Initial connection

+    buf2i(&buf[i][HEADER_LEN], connStat[i].id);

+    // Log("This connection's id: %d", connStat[i].id);

+    connStat[i].direction = header.m_direction;

+    connStat[i].linkType = FILE_LINK;

+    connStat[i].lastTime = currentTime;

+    connStat[i].expectingHeader = true;

+    connStat[i].nBuffered = 0;

+    connStat[i].nToDo = HEADER_LEN;

+    connStat[i].shouldClose =

+        true; // flag to close this connection once it's processed

+

+    for (int x = 1; x <= nConns; x++) {

+      if ((connStat[x].direction == C2S) &&

+          (connStat[x].linkType == MESSAGE_LINK) &&

+          (connStat[x].id == connStat[i].id)) {

+        strcat(connStat[i].name, connStat[x].name);

+        connStat[i].isLoggedIn = connStat[x].isLoggedIn;

+        foundActiveUser = true;

+        s2cConnNumb = x;

+        break;

+      }

+    }

+

+    if (s2cConnNumb == -1) {

+      Log("Enexpected state. Recieved %s on new connection without S2C "

+          "connection for messages.",

+          com2str(header.m_command));

+    } else if (!connStat[i].isLoggedIn) {

+      Log("[%s : %s] Failed: Connection %d is not logged in.", connStat[i].name,

+          com2str(header.m_command), i);

+      outHeader.setFlags(S2C, FAIL, PUB, SIGN);

+      outHeader.m_command = SEND; // avoid file transfer logic on client side

+      memcpy(outHeader.m_name, NAME, strlen(NAME));

+      strcat(message, "Users must be logged in to '");

+      strcat(message, com2str(header.m_command));

+      strcat(message, "'. Login with '");

+      strcat(message, com2str(LOGIN));

+      strcat(message, " [username] [password]'.");

+      outHeader.m_size = strlen(message);

+      sendMessageToId(connStat[i].id, false, outHeader, message);

+    } else {

+      // Save the file

+      nextFileId = getNumEntries(FILE_DATABASE);

+      if (nextFileId == -1) {

+        Log("Enexpected state. %s next File Id of -1.", FILE_DATABASE);

+      } else {

+        snprintf(server_filename, sizeof(server_filename), "%s/%d_", FILES_DIR,

+                 nextFileId);

+        offset = HEADER_LEN + 4;

+        buf2i(&buf[i][offset], filenameLen); // first 4 bytes is client id

+        offset += 4;

+        memcpy(&server_filename[strlen(server_filename)], &buf[i][offset],

+               filenameLen);

+        memcpy(filename, &buf[i][offset], filenameLen);

+        offset += filenameLen;

+        buf2i(&buf[i][offset], fileLen);

+        offset += 4;

+        // Log("[%s : %s] Saving file: %s", server_filename);

+        fp = fopen(FILE_DATABASE, "a");

+        fputs(server_filename, fp);

+        fputs("\n", fp);

+        fclose(fp);

+        buf2file(&buf[i][offset], fileLen, server_filename);

+

+        // Send SENDF/SENDF2 message to interested parties

+        outHeader.setFlags(S2C, SUCCESS, header.m_recipient,

+                           SIGN); // will update recipient as necessary

+        outHeader.m_command = header.m_command;

+        memcpy(outHeader.m_name, connStat[i].name, strlen(connStat[i].name));

+        i2buf(nextFileId, intbuf);

+        memcpy(message, intbuf, 4);

+        offset = 4;

+        memcpy(&message[offset], &buf[i][HEADER_LEN + 8], filenameLen);

+        offset += filenameLen;

+        outHeader.m_size = offset;

+

+        if (header.m_command == SENDF) {

+          Log("[%s : %s] %s", connStat[i].name, com2str(header.m_command),

+              filename);

+          sendMessageToAllLoggedInExceptSender(connStat[i].id, outHeader,

+                                               message);

+        } else {

+          memcpy(username, header.m_name, MAX_USERNAME_LEN);

+          Log("[%s : %s %s] %s", connStat[i].name, com2str(header.m_command),

+              username, filename);

+          sendMessageToName(username, outHeader, message);

+        }

+      }

+    }

+    break;

+  case GETF:

+    buf2i(&buf[i][HEADER_LEN], connStat[i].id);

+    // header name is origional sender. Find client's name with client id

+    for (int x = 1; x <= nConns; x++) {

+      if ((connStat[i].id == connStat[x].id) &&

+          (connStat[x].direction == C2S) &&

+          (connStat[x].linkType == MESSAGE_LINK)) {

+        memcpy(connStat[i].name, connStat[x].name, MAX_USERNAME_LEN);

+        break;

+      }

+    }

+    buf2i(&buf[i][HEADER_LEN + 4], fileId);

+    connStat[i].direction = S2C;

+    connStat[i].linkType = FILE_LINK;

+    connStat[i].lastTime = currentTime;

+    // no need for shouldClose. Client will close connection and periodic ping will

+    // detect closure

+

+    snprintf(server_filename, sizeof(server_filename), "%s/%d_", FILES_DIR,

+             fileId);

+    memcpy(&server_filename[strlen(server_filename)], &buf[i][HEADER_LEN + 8],

+           header.m_size - 8);

+

+    memcpy(filename, &buf[i][HEADER_LEN + 8], header.m_size - 8);

+    filenameLen = strlen(filename);

+

+    // Log("Getting file %s", server_filename);

+    memset(buf[i], 0, BUF_LEN);

+

+    // Check that the file exists

+    fp = fopen(server_filename, "r");

+    if (fp) {

+      fclose(fp);

+      outHeader.setFlags(S2C, SUCCESS, header.m_recipient,

+                         SIGN); // will update recipient as necessary

+      if (header.m_command == SENDF2)

+        outHeader.m_recipient = PRIV;

+      outHeader.m_command = header.m_command;

+      memcpy(outHeader.m_name, header.m_name,

+             MAX_USERNAME_LEN); // pass along origional sender

+      offset = HEADER_LEN;

+      i2buf(filenameLen, &buf[i][offset]); // encode filename length

+      offset += 4;

+      memcpy(&buf[i][offset], filename,

+             strlen(filename)); // encode the filename

+      offset += strlen(filename);

+      fileLen = file2buf(server_filename, &buf[i][offset + 4]);

+      i2buf(fileLen, &buf[i][offset]);

+      offset += 4 + fileLen;

+      outHeader.m_size = offset - HEADER_LEN;

+      outHeader.encode(buf[i]);

+

+      connStat[i].nBuffered = offset;

+      connStat[i].messageLen = offset;

+      connStat[i].nToDo = offset;

+      peers[i].events &= ~POLLRDNORM;

+      peers[i].events |= POLLWRNORM;

+

+      Log("[%s : %s] %s", connStat[i].name, com2str(header.m_command),

+          filename);

+    } else {

+      Log("File not found: %s", filename);

+      // TODO: Send message if file is not found

+    }

+    break;

+  case LIST:

+    Log("[%s : %s]", connStat[i].name, com2str(header.m_command));

+    outHeader.setFlags(S2C, SUCCESS, PUB, SIGN);

+    outHeader.m_command = LIST;

+    memcpy(outHeader.m_name, NAME, strlen(NAME));

+    for (int x = 1; x <= nConns; x++) {

+      if ((connStat[x].direction == C2S) &&

+          (connStat[x].linkType == MESSAGE_LINK) && (connStat[x].isLoggedIn)) {

+        numLoggedIn++;

+      }

+    }

+    snprintf(message, sizeof(message), "%d", numLoggedIn);

+    strcat(message, " user(s) currently logged in:");

+    for (int x = 1; x <= nConns; x++) {

+      if ((connStat[x].direction == C2S) &&

+          (connStat[x].linkType == MESSAGE_LINK) && (connStat[x].isLoggedIn)) {

+        strcat(message, "\n\t");

+        strcat(message, connStat[x].name);

+      }

+    }

+    outHeader.m_size = strlen(message);

+    sendMessageToId(connStat[i].id, false, outHeader, message);

+    break;

+  case PING:

+    // Log("Ping from %s", header.m_name);

+    asm("nop"); // do nothing

+    break;

+  default:

+    Log("No doServerCommand() for command %s", com2str(header.m_command));

+  }

+}

+

+// Send the message to every S2C with the specified id. If the reqLoggedIn

+// flag is set, require that the connection is logged in.

+void sendMessageToId(int id, bool reqLoggedIn, Header header, char *message) {

+  for (int i = 1; i <= nConns; i++) {

+    if ((connStat[i].direction == S2C) && (id == connStat[i].id)) {

+      if (reqLoggedIn) {

+        if (connStat[i].isLoggedIn) {

+          prepareMessage(i, header, message);

+        }

+      } else {

+        prepareMessage(i, header, message);

+      }

+    }

+  }

+}

+

+// Send the message to every S2C which is logged in.

+void sendMessageToAllLoggedIn(Header header, char *message) {

+  for (int i = 1; i <= nConns; i++) {

+    if ((connStat[i].direction == S2C) && connStat[i].isLoggedIn) {

+      prepareMessage(i, header, message);

+    }

+  }

+}

+

+// Send the message to every s2cConnNumb

+void sendMessageToAllLoggedInExceptSender(int senderID, Header header,

+                                          char *message) {

+  for (int i = 1; i <= nConns; i++) {

+    if ((connStat[i].direction == S2C) && connStat[i].isLoggedIn &&

+        (connStat[i].id != senderID)) {

+      prepareMessage(i, header, message);

+    }

+  }

+}

+

+// Send the message to all loged in users with the specified name.

+void sendMessageToName(char *name, Header header, char *message) {

+  for (int i = 1; i <= nConns; i++) {

+    if ((connStat[i].direction == S2C) && connStat[i].isLoggedIn &&

+        (strcmp(name, connStat[i].name) == 0)) {

+      prepareMessage(i, header, message);

+    }

+  }

+}

+

+// Load a message into a connection

+void prepareMessage(int i, Header header, char *message) {

+  if (connStat[i].direction == S2C) {

+    int offset = connStat[i].nBuffered;

+

+    // Log("Preparing message for connection %d", i);

+    // header.displayContents(true);

+    // Log("Message: |%s|", message);

+    // Log("offset: %d, nBuffered: %d, nToDo: %d: messageLen: %d", offset,

+    // connStat[i].nBuffered, connStat[i].nToDo, connStat[i].messageLen);

+

+    header.encode(&buf[i][offset]);

+    memcpy(&buf[i][offset + HEADER_LEN], message, header.m_size);

+

+    connStat[i].nBuffered += HEADER_LEN + header.m_size;

+    if (connStat[i].nToDo == 0) {

+      connStat[i].messageLen = HEADER_LEN + header.m_size;

+      connStat[i].nToDo = HEADER_LEN + header.m_size;

+    }

+

+    peers[i].events |= POLLWRNORM;

+  } else {

+    Log("[%s] WARNING: attempted to write to C2S connection %d", NAME,

+        i);

+  }

+}

+

+void printServerCommand(int i) {

+  Header h;

+  h.decode(buf[i]);

+

+  Log("[%s]: [%s, %s, %s, %s] [%s]  [%s]  [%d]", connStat[i].name,

+      !h.m_direction ? "C2S" : "S2C", !h.m_flag ? "SUCCESS" : "FAIL",

+      !h.m_recipient ? "PUB" : "PRIV", !h.m_trace ? "SIGN" : "ANNON",

+      com2str(h.m_command), h.m_name, h.m_size);

+

+  if (h.m_size > 0)

+    Log("\tData: [%s]", buf[i] + HEADER_LEN);

+}

+

+int main(int argc, char **argv) {

+  if (argc != 2) {

+    Log("Usage: %s reset", argv[0]);

+    Log("Usage: %s [server Port]", argv[0]);

+    return -1;

+  }

+

+  if (strcmp("reset", argv[1]) == 0) {

+    Log("Resetting server databases");

+    clearDatabase(USER_DATABASE);

+    clearDatabase(FILE_DATABASE);

+

+    int status;

+    pid_t cpid;

+

+    if ((cpid = fork()) == -1) {

+      perror("fork");

+      return 1;

+    }

+

+    if (cpid == 0) { // Child process executes "rm -rf users"

+      char command[40] = "rm -rf files"; // only way this worked

+      char *args[5] = {NULL};

+      args[0] = strtok(command, " ");

+      for (int i = 1; i < 3; i++)

+        args[i] = strtok(NULL, " ");

+      execvp(args[0], args);

+      return 0;

+    } else { // Parent process waits for "rm -rf users" to finish

+      pid_t rpid;

+      int status;

+      if ((rpid = wait(NULL)) == -1)

+        perror("wait");

+      else {

+        Log("Clearing file storage");

+        if (mkdir(FILES_DIR, S_IRWXU | S_IRWXG | S_IRWXO) != 0) {

+          perror("mkdir");

+          return -1;

+        }

+      }

+      return 0;

+    }

+  }

+

+  // Make files directory if it doesn't exist

+  DIR *pDir;

+  struct stat s;

+

+  if (stat("files", &s) != 0) {

+    // The files directory doesn't exist

+    if (mkdir("files", S_IRWXU | S_IRWXG | S_IRWXO) != 0) {

+      perror("mkdir");

+      return -1;

+    }

+  }

+

+  int port = atoi(argv[1]);

+  DoServer(port);

+

+  return 0;

+}

diff --git a/src/util.cpp b/src/util.cpp
new file mode 100644
index 0000000..142fcbd
--- /dev/null
+++ b/src/util.cpp
@@ -0,0 +1,398 @@
+#include <string>
+#include <string.h>
+#include <cstddef>
+#include <stdio.h>
+#include <stdarg.h>
+#include <time.h>
+#include <sys/timeb.h>
+
+#include "util.hpp"
+
+#define VALID_CHARACTERS "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+
+enum Command parse_command(char* line){
+  /* Find a valid command in the first word of the line (case sensitive)
+  args:
+    line (char*): string of characters from the input file
+
+  returns:
+    (command): Returns the found command. Returns else if first word is invalid.
+  */
+  if (line == NULL){
+    return INVALID;
+  }
+
+  char* rest;
+  char* tok = strtok_r(line, " ", &rest);
+
+  if (tok == NULL){
+    return INVALID;
+  }
+
+  // REGISTER [username] [password]
+  if (strcmp(tok, "REGISTER") == 0){
+    char* username = strtok_r(rest, " ", &rest);
+    if(!isValidUsername(username)) return INVALID;
+
+    char* password = strtok_r(rest, " ", &rest);
+    if(password == NULL) return INVALID;
+    if(!isValidPassword(password)) return INVALID;
+
+    char* misc = strtok_r(rest, " ", &rest);
+    if(misc != NULL) return INVALID;
+
+    return REGISTER;
+  }
+
+  // LOGIN [username] [password]
+  if (strcmp(tok, "LOGIN") == 0){
+    char* username = strtok_r(rest, " ", &rest);
+    if(!isValidUsername(username)) return INVALID;
+
+    char* password = strtok_r(rest, " ", &rest);
+    if(password == NULL) return INVALID;
+    if(!isValidPassword(password)) return INVALID;
+
+    char* misc = strtok_r(rest, " ", &rest);
+    if(misc != NULL) return INVALID;
+
+    return LOGIN;
+  }
+
+  // LOGOUT
+  if (strcmp(tok, "LOGOUT") == 0){
+    char* misc = strtok_r(rest, " ", &rest);
+    if(misc != NULL) return INVALID;
+
+    return LOGOUT;
+  }
+
+  // SEND [msg]
+  if (strcmp(tok, "SEND") == 0){
+    if (int(strlen(rest) == 0)) return INVALID;
+
+    return SEND;
+  }
+
+  // SEND2 [username] [msg]
+  if (strcmp(tok, "SEND2") == 0){
+    char* username = strtok_r(rest, " ", &rest);
+    if(!isValidUsername(username)) return INVALID;
+
+    if (int(strlen(rest) == 0)) return INVALID;
+
+    return SEND2;
+  }
+
+  // SENDA [msg]
+  if (strcmp(tok, "SENDA") == 0){
+    if (int(strlen(rest) == 0)) return INVALID;
+
+    return SENDA;
+  }
+
+  // SENDA2 [username] [msg]
+  if (strcmp(tok, "SENDA2") == 0){
+    char* username = strtok_r(rest, " ", &rest);
+    if(!isValidUsername(username)) return INVALID;
+
+    if (int(strlen(rest) == 0)) return INVALID;
+
+    return SENDA2;
+  }
+
+  // SENDF [local file]
+  if (strcmp(tok, "SENDF") == 0){
+    char* file_name = strtok_r(rest, " ", &rest);
+    if(file_name == NULL) return INVALID;
+
+    if (int(strlen(rest) != 0)) return INVALID;
+
+    return SENDF;
+  }
+
+  // SENDF2 [username] [local file]
+  if (strcmp(tok, "SENDF2") == 0){
+    char* username = strtok_r(rest, " ", &rest);
+    if(!isValidUsername(username)) return INVALID;
+
+    char* file_name = strtok_r(rest, " ", &rest);
+    if(file_name == NULL) return INVALID;
+
+    if (int(strlen(rest) != 0)) return INVALID;
+
+    return SENDF2;
+  }
+
+  // LIST
+  if (strcmp(tok, "LIST") == 0){
+    char* misc = strtok_r(rest, " ", &rest);
+    if(misc != NULL) return INVALID;
+
+    return LIST;
+  }
+
+  // DELAY
+  if (strcmp(tok, "DELAY") == 0){
+    char* delay_time = strtok_r(rest, " ", &rest);
+    if(delay_time == NULL) return INVALID;
+
+    std::string str(delay_time);
+    std::size_t found = str.find_first_not_of("0123456789");
+    if(found != std::string::npos) return INVALID;
+
+    if (int(strlen(rest) != 0)) return INVALID;
+
+    return DELAY;
+  }
+
+  // default
+  return INVALID;
+}
+
+
+bool isValidUsername(char* username){
+  /* Helper function to check if a username string is valid
+  args:
+    username (char*): Username to be tested.
+
+  returns:
+    bool: Username is valid ? true, false
+  */
+  if(username == NULL) return false;
+  else if ((strlen(username) > MAX_USERNAME_LEN)||(strlen(username) < MIN_USERNAME_LEN)) return false;
+  else{
+    std::string str(username);
+    std::size_t found = str.find_first_not_of(VALID_CHARACTERS);
+    if(found != std::string::npos) return false;
+  }
+
+  return true;
+}
+
+
+bool isValidPassword(char* password){
+  if(password == NULL) return false;
+  else if ((strlen(password) > MAX_PASSWORD_LEN)||(strlen(password) < MIN_PASSWORD_LEN)) return false;
+  else{
+    std::string str(password);
+    std::size_t found = str.find_first_not_of(VALID_CHARACTERS);
+    if(found != std::string::npos) return false;
+  }
+
+  return true;
+}
+
+
+void Error(const char * format, ...) {
+	char msg[4096];
+	va_list argptr;
+	va_start(argptr, format);
+	vsprintf(msg, format, argptr);
+	va_end(argptr);
+	fprintf(stderr, "Error: %s\n", msg);
+	exit(-1);
+}
+
+void Log(const char * format, ...) {
+	char msg[2048];
+	va_list argptr;
+	va_start(argptr, format);
+	vsprintf(msg, format, argptr);
+	va_end(argptr);
+	fprintf(stderr, "%s\n", msg);
+}
+
+// convert buf[0:3] to int
+void buf2i(BYTE * buf, int &i){
+  // No way to avoid Segmentation fault. Some bytes may be 0
+  i = 0;
+  i += buf[3];
+  i += ((int)(buf[2])) << 8;
+  i += ((int)(buf[1])) << 16;
+  i += ((int)(buf[0])) << 24;
+}
+
+// convert int to buf[4] where buf[0] contains MSB's and buf[3] contains LSB's
+void i2buf(int &i, BYTE * buf){
+  // No way to avoid Segmentation fault. Some bytes may be 0
+  buf[0] = (BYTE)((i & 0xFF000000) >> 24);
+  buf[1] = (BYTE)((i & 0x00FF0000) >> 16);
+  buf[2] = (BYTE)((i & 0x0000FF00) >> 8);
+  buf[3] = (BYTE)(i & 0x000000FF);
+}
+
+const char * com2str(enum Command command){
+  const char * com2str[] = {"REGISTER",
+                            "LOGIN",
+                            "LOGOUT",
+                            "SEND",
+                            "SEND2",
+                            "SENDA",
+                            "SENDA2",
+                            "SENDF",
+                            "SENDF2",
+                            "LIST",
+                            "DELAY",
+                            "GETF",
+                            "PING",
+                            "CONNECT",
+                            "",
+                            "INVALID"
+                          };
+    return com2str[command];
+}
+
+// Computes the difference between times a and b in seconds
+// a - b = result
+double timeDifference(struct timeb a, struct timeb b){
+  return (a.time + a.millitm / (double) 1000.0f) - (b.time + b.millitm / (double) 1000.0f);
+}
+
+int getNumEntries(const char* database){
+  FILE* fp = fopen(database, "r");
+  if (!fp){
+    Log("Username check failed to open the file: %s", database);
+    return -1;
+  }
+
+  int numEntries = 0;
+
+  char line[LINE_SIZE] = {0};
+  while(fgets(line, LINE_SIZE, fp) != NULL){
+    char* new_line_pos = strchr(line, '\n');
+    if(new_line_pos != NULL)
+      *new_line_pos = 0;
+    // Including blank lines as entries. Don't use any blank lines.
+    numEntries++;
+    memset(line, 0, LINE_SIZE);
+  }
+
+  fclose(fp);
+  return numEntries;
+}
+
+// User/password is in registry: true
+// User/password is not in registry: false
+bool loginQuery(const char * database, char* username, char* password){
+  FILE* fp = fopen(database, "r");
+  if (!fp){
+    Log("Registry check failed to open the file: %s", database);
+    return false;
+  }
+
+  char line[LINE_SIZE] = {0};
+  while(fgets(line, LINE_SIZE, fp) != NULL){
+    char* new_line_pos = strchr(line, '\n');
+    if(new_line_pos != NULL)
+      *new_line_pos = 0;
+
+    char* rest;
+    char* usr = strtok_r(line, " ", &rest);
+    char* pswd = strtok_r(rest, " ", &rest);
+
+    //Log("username: |%s|   Password: |%s|", usr, pswd);
+
+    if((strcmp(username, usr) == 0) && (strcmp(password, pswd) == 0)){
+      fclose(fp);
+      return true;
+    }
+
+    memset(line, 0, LINE_SIZE);
+  }
+
+  fclose(fp);
+  return false;
+}
+
+// User is in registry: true
+// User is not in registry: false
+bool usernameQuery(const char * database, char* username){
+  FILE* fp = fopen(database, "r");
+  if (!fp){
+    Log("Username check failed to open the file: %s", database);
+    return false;
+  }
+
+  char line[LINE_SIZE] = {0};
+  while(fgets(line, LINE_SIZE, fp) != NULL){
+    char* new_line_pos = strchr(line, '\n');
+    if(new_line_pos != NULL)
+      *new_line_pos = 0;
+
+    char* rest;
+    char* usr = strtok_r(line, " ", &rest);
+
+    //Log("username: |%s|", usr);
+
+    if(strcmp(username, usr) == 0){
+      fclose(fp);
+      return true;
+    }
+
+    memset(line, 0, LINE_SIZE);
+  }
+
+  fclose(fp);
+  return false;
+}
+
+void recordEntry(const char * database, char* key, char* value){
+  FILE* fp = fopen(database, "a");
+
+  if (!fp){
+    Log("Registry append failed to open the file: %s", database);
+    return;
+  }
+
+  char line[LINE_SIZE] = {0};
+  strcat(line, key);
+  strcat(line, " ");
+  strcat(line, value);
+  strcat(line, "\n");
+
+  fputs(line, fp);
+  fclose(fp);
+}
+
+void clearDatabase(const char * database){
+  FILE* fp = fopen(database, "w");
+  fclose(fp);
+}
+
+
+int buf2file(BYTE* buf, int nbytes, char* filename){
+  FILE* f = fopen(filename, "w");
+  if(!f) return -1;
+
+  fwrite(buf, 1, nbytes, f);
+  fclose(f);
+  return 0;
+}
+
+
+int file2buf(char* filename, BYTE* buf){
+  FILE* f = fopen(filename, "r");
+  if(!f){
+    Log("Error: Cannot open %s", filename);
+    return -1;
+  }
+
+  fseek(f, 0, SEEK_END);  // jump to end of file
+  long nbytes = ftell(f);  // find current offset on file f
+  fseek(f, 0, SEEK_SET);  // jump to beginning of file
+
+  if(nbytes > MAX_REQUEST_SIZE){
+    Log("Error: File %s is too big: %d", filename, nbytes);
+    return -1;
+  }
+
+  int nread = fread(buf, 1, nbytes, f);
+  if(nread != nbytes){
+    Log("Error: Byte count mismatch with fread: %d, %d", nbytes, nread);
+    return -1;
+  }
+
+  fclose(f);
+  return nbytes;
+}
diff --git a/tests/a.user1.txt b/tests/a.user1.txt
new file mode 100644
index 0000000..20f6ae8
--- /dev/null
+++ b/tests/a.user1.txt
@@ -0,0 +1,4 @@
+REGISTER mario foobar00
+DELAY 1
+LOGIN mario foobar00
+DELAY 9999
diff --git a/tests/a.user2.txt b/tests/a.user2.txt
new file mode 100644
index 0000000..6dda110
--- /dev/null
+++ b/tests/a.user2.txt
@@ -0,0 +1,4 @@
+REGISTER luigi foobar00
+DELAY 1
+LOGIN luigi foobar00
+DELAY 9999
diff --git a/tests/b.user1.txt b/tests/b.user1.txt
new file mode 100644
index 0000000..20f6ae8
--- /dev/null
+++ b/tests/b.user1.txt
@@ -0,0 +1,4 @@
+REGISTER mario foobar00
+DELAY 1
+LOGIN mario foobar00
+DELAY 9999
diff --git a/tests/b.user2.txt b/tests/b.user2.txt
new file mode 100644
index 0000000..45203e6
--- /dev/null
+++ b/tests/b.user2.txt
@@ -0,0 +1,6 @@
+REGISTER luigi foobar00
+DELAY 1
+LOGIN luigi foobar00
+DELAY 1
+SEND HELLOWORLD
+DELAY 9999
diff --git a/tests/c.user1.txt b/tests/c.user1.txt
new file mode 100644
index 0000000..20f6ae8
--- /dev/null
+++ b/tests/c.user1.txt
@@ -0,0 +1,4 @@
+REGISTER mario foobar00
+DELAY 1
+LOGIN mario foobar00
+DELAY 9999
diff --git a/tests/c.user2.txt b/tests/c.user2.txt
new file mode 100644
index 0000000..704b379
--- /dev/null
+++ b/tests/c.user2.txt
@@ -0,0 +1,6 @@
+REGISTER luigi foobar00
+DELAY 1
+LOGIN luigi foobar00
+DELAY 1
+SENDF2 mario 1kb.user2
+DELAY 9999
diff --git a/tests/d.user1.txt b/tests/d.user1.txt
new file mode 100644
index 0000000..20f6ae8
--- /dev/null
+++ b/tests/d.user1.txt
@@ -0,0 +1,4 @@
+REGISTER mario foobar00
+DELAY 1
+LOGIN mario foobar00
+DELAY 9999
diff --git a/tests/d.user2.txt b/tests/d.user2.txt
new file mode 100644
index 0000000..6dda110
--- /dev/null
+++ b/tests/d.user2.txt
@@ -0,0 +1,4 @@
+REGISTER luigi foobar00
+DELAY 1
+LOGIN luigi foobar00
+DELAY 9999
diff --git a/tests/d.user3.txt b/tests/d.user3.txt
new file mode 100644
index 0000000..bf28b7b
--- /dev/null
+++ b/tests/d.user3.txt
@@ -0,0 +1,12 @@
+REGISTER wario foobar00
+DELAY 1
+LOGIN wario foobar00
+DELAY 1
+SENDF 1mb.1.user3
+SENDF 1mb.2.user3
+SENDF 1mb.3.user3
+SENDF 1mb.4.user3
+SENDF 1mb.5.user3
+SENDF 1mb.6.user3
+SENDF 1mb.7.user3
+DELAY 9999