// Module Name: Server.c
//
// Description:
//    This example illustrates a simple TCP server that accepts 
//    incoming client connections. Once a client connection is 
//    established, a thread is spawned to read data from the 
//    client and echo it back (if the echo option is not 
//    disabled).
//
// Compile:
//    cl -o Server Server.c ws2_32.lib
//
// Command line options:
//    server [-p:x] [-i:IP] [-o]
//           -p:x      Port number to listen on
//           -i:str    Interface to listen on
//           -o        Receive only, don't echo the data back
//
#include <winsock2.h>

#include <stdio.h>
#include <stdlib.h>

#define DEFAULT_PORT        5150
#define DEFAULT_BUFFER      4096

int    iPort      = DEFAULT_PORT; // Port to listen for clients on
BOOL   bInterface = FALSE,	 // Listen on the specified interface
       bRecvOnly  = FALSE;   // Receive data only; don't echo back
char   szAddress[128];       // Interface to listen for clients on

//
// Function: usage
//
// Description:
//    Print usage information and exit
//
void usage()
{
    printf("usage: server [-p:x] [-i:IP] [-o]\n\n");
    printf("       -p:x      Port number to listen on\n");
    printf("       -i:str    Interface to listen on\n");
    printf("       -o        Don't echo the data back\n\n");
    ExitProcess(1);
}
  
//
// Function: ValidateArgs
//
// Description:
//    Parse the command line arguments, and set some global flags 
//    to indicate what actions to perform
//
void ValidateArgs(int argc, char **argv)
{
    int i;

    for(i = 1; i < argc; i++)
    {
        if ((argv[i][0] == '-') || (argv[i][0] == '/'))
        {
            switch (tolower(argv[i][1]))
            {
                case 'p':
                    iPort = atoi(&argv[i][3]);
                    break;
                case 'i':
                    bInterface = TRUE;
                    if (strlen(argv[i]) > 3)
                        strcpy(szAddress, &argv[i][3]);
                    break;
                   case 'o':
		           bRecvOnly = TRUE;
                       break;
                default:
                    usage();
                    break;
            }
        }
    }
}

//
// Function: ClientThread
//
// Description:
//    This function is called as a thread, and it handles a given
//    client connection.  The parameter passed in is the socket 
//    handle returned from an accept() call.  This function reads
//    data from the client and writes it back.
//
DWORD WINAPI ClientThread(LPVOID lpParam)
{
    SOCKET        sock=(SOCKET)lpParam;
    char          szBuff[DEFAULT_BUFFER];
    int           ret,
                  nLeft,
                  idx;

    while(1)
    {
        // Perform a blocking recv() call
        //
        ret = recv(sock, szBuff, DEFAULT_BUFFER, 0);
        if (ret == 0)        // Graceful close
            break;
        else if (ret == SOCKET_ERROR)
        {
            printf("recv() failed: %d\n", WSAGetLastError());
            break;
        }
        szBuff[ret] = '\0';
        printf("RECV: '%s'\n", szBuff);
        //
        // If we selected to echo the data back, do it 
        //
        if (!bRecvOnly)
        {
            nLeft = ret;
            idx = 0;
			//
            // Make sure we write all the data
            //
            while(nLeft > 0)
            {
                ret = send(sock, &szBuff[idx], nLeft, 0);
                if (ret == 0)
                    break;
                else if (ret == SOCKET_ERROR)
                {
                    printf("send() failed: %d\n", 
                        WSAGetLastError());
                    break;
                }
                nLeft -= ret;
                idx += ret;
               }
        }
    }
    return 0;
}

//
// Function: main
//
// Description:
//    Main thread of execution. Initialize Winsock, parse the
//    command line arguments, create the listening socket, bind
//    to the local address, and wait for client connections.
//
int main(int argc, char **argv)
{
    WSADATA       wsd;
    SOCKET        sListen,
                  sClient;
    int           iAddrSize;
    HANDLE        hThread;
    DWORD         dwThreadId;
    struct sockaddr_in local,
                       client;

    ValidateArgs(argc, argv);
    if (WSAStartup(MAKEWORD(2,2), &wsd) != 0)
    {
        printf("Failed to load Winsock!\n");
        return 1;
    }
    // Create our listening socket
    //
    sListen = socket(AF_INET, SOCK_STREAM, IPPROTO_IP);
    if (sListen == SOCKET_ERROR)
    {
        printf("socket() failed: %d\n", WSAGetLastError());
        return 1;
    }
    // Select the local interface and bind to it
    //
    if (bInterface)
    {
        local.sin_addr.s_addr = inet_addr(szAddress);
        if (local.sin_addr.s_addr == INADDR_NONE)
            usage();
    }
    else
        local.sin_addr.s_addr = htonl(INADDR_ANY);
    local.sin_family = AF_INET;
    local.sin_port = htons(iPort);

    if (bind(sListen, (struct sockaddr *)&local, 
            sizeof(local)) == SOCKET_ERROR)
    {
        printf("bind() failed: %d\n", WSAGetLastError());
        return 1;
    }
    listen(sListen, 8);
    //
    // In a continous loop, wait for incoming clients. Once one 
    // is detected, create a thread and pass the handle off to it.
    //
    while (1)
    {
        iAddrSize = sizeof(client);
        sClient = accept(sListen, (struct sockaddr *)&client,
                        &iAddrSize);        
        if (sClient == INVALID_SOCKET)
        {        
            printf("accept() failed: %d\n", WSAGetLastError());
            break;
        }
        printf("Accepted client: %s:%d\n", 
            inet_ntoa(client.sin_addr), ntohs(client.sin_port));

        hThread = CreateThread(NULL, 0, ClientThread, 
                    (LPVOID)sClient, 0, &dwThreadId);
        if (hThread == NULL)
        {
            printf("CreateThread() failed: %d\n", GetLastError());
            break;
        }
        CloseHandle(hThread);
    }
    closesocket(sListen);
    
    WSACleanup();
    return 0;
}