Использование протокола TCP/IP

#pragma argsused
int main(int argc, char* argv[]) {
    char clientRequest[REQUEST_MSG_SIZE];
    sockaddr_in  serverAddr;     //server's socket address
    int sockAddrSize;            //size of socket address structure
    SOCKET sHandle;              //socket descriptor
    unsigned nbyte;              //number of sended bytes
    double starttime, endtime;
    unsigned mlen;             //message's length 
    char* serverName;          //server's name
    WSADATA wsaData;           //data structure that is to receive
                               //details of the Windows Sockets 
                               //implementation

   serverName = argv[1];

   //initiate use of WS2_32.DLL by a process
   if(WSAStartup(MAKEWORD(1, 1), &wsaData)) {
        getSocketError();
        getch();
        return 0;
   }

   //create client's socket
   if((sHandle = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) 
   {
        getSocketError();
        getch();
        return 0;
   }

   // build server socket address
   sockAddrSize = sizeof(sockaddr_in);
   memset(&serverAddr, 0, sockAddrSize);
   serverAddr.sin_family = AF_INET;
   serverAddr.sin_port = htons(SERVER_PORT_NUM);

   if((serverAddr.sin_addr.s_addr = inet_addr(serverName)) 
                             == INADDR_NONE) 
   {
       perror("unknown server name");
       closesocket(sHandle);
       getch();
       return 0;
   }

   //connect to server
   if(connect(sHandle, (sockaddr *)&serverAddr,
                 sockAddrSize) == -1)
   {
       getSocketError();
       closesocket(sHandle);
       getch();
       return 0;
   }

   //fill string to send
   printf("Introduce the string to send:\n");
   gets(clientRequest);
   mlen = strlen(clientRequest);
   if(mlen >= REQUEST_MSG_SIZE) {
       printf("Max length of message is %d bytes !\n", 
               REQUEST_MSG_SIZE-1);
       getch();
       return 0;
   }

   //send request to server
   starttime = ctime();
   if((nbyte = send(sHandle, (char *)clientRequest,
                  mlen, MSG_DONTROUTE)) == SOCKET_ERROR)
   {
      getSocketError();
      closesocket(sHandle);
      getch();
      return 0;
   }

   if(nbyte != mlen)
          printf("Write only %d (%d) bytes\n", nbyte, mlen);

   endtime = ctime() - starttime;
   printf("send_time = %f\n", (float)endtime);
   closesocket(sHandle);

   printf("Press any key\n");
   getch();
   return 0;
}

void getSocketError() {
   LPVOID lpMsgBuf;
   if (!FormatMessage(
       FORMAT_MESSAGE_ALLOCATE_BUFFER |
       FORMAT_MESSAGE_FROM_SYSTEM |
       FORMAT_MESSAGE_IGNORE_INSERTS,
       NULL,
       GetLastError(),
       MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
       (LPTSTR) &lpMsgBuf,
       0,
       NULL ))
   {
      MessageBox(NULL, "Error number not found",
                 "Error", MB_OK | MB_ICONSTOP );
      return;
   }
   // Display the string.
   MessageBox(NULL, (LPCTSTR)lpMsgBuf, "Error",
               MB_OK | MB_ICONSTOP);
   // Free the buffer.
   LocalFree(lpMsgBuf);
}

int main() {
   sockaddr_in serverAddr;       // server's socket address
   sockaddr_in clientAddr;       // client's socket address
   int sockAddrSize;             // size of socket address structure
   SOCKET sHandle;               // socket file descriptor
   SOCKET newSHandle;            // socket descriptor from accept
   WSADATA wsaData;      //data structure that is to receive details
                         //of the Windows Sockets implementation
   int nbyte = 0;        //number of sended bytes
   char clientRequest[REQUEST_MSG_SIZE];

   // set up the local address
   sockAddrSize = sizeof(sockaddr_in);
   memset(&serverAddr, 0, sockAddrSize);
   serverAddr.sin_family = AF_INET;
   serverAddr.sin_port = htons(SERVER_PORT_NUM);
   serverAddr.sin_addr.s_addr = INADDR_ANY;

   // initiate use of WS2_32.DLL by a process
   if(WSAStartup(MAKEWORD(1, 1), &wsaData)) {
       getSocketError();
       getch();
       return 0;
   }

   // create a TCP-based socket
   if((sHandle = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) {
       getSocketError();
       getch();
       return 0;
   }

   // bind socket to local address
   if(bind(sHandle, (sockaddr *)&serverAddr,
            sockAddrSize)  == -1 )
   {
       getSocketError();
       closesocket(sHandle);
       getch();
       return 0;
   }

   // create queue for client connection requests
   if(listen(sHandle, SERVER_MAX_CONNECTIONS) == -1) {
       getSocketError();
       closesocket(sHandle);
       getch();
       return 0;
   }

   // accept new connect requests and spawn tasks to process them
   // Note: newSHandle socket will take propreties of
   // sHandle socket
   if((newSHandle = accept(sHandle, (sockaddr *)&clientAddr,
                              &sockAddrSize)) == INVALID_SOCKET)
   {
       getSocketError();
       closesocket(sHandle);
       getch();
       return 0;
   }

   nbyte = recv(newSHandle, (char *)clientRequest,
                 sizeof(clientRequest), MSG_PEEK);
   if (nbyte != SOCKET_ERROR) {
       printf("Have received %d bytes \n", nbyte);
       printf("Data: %s\n", clientRequest);
   }
   else
       getSocketError();

   memset(clientRequest, 0, REQUEST_MSG_SIZE);
   closesocket(sHandle);
   closesocket(newSHandle);
   printf("Press any key\n");
   getch();
   return 0;
}