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connect, socket API, is sending the connection request after long delay Options RRS feed

  • Pergunta

  • Hello All,

    In our application we need to communication with multiple devices
    simultaneously. We're creating threads to communicate with individual
    devices. We're are using non-blocking sockets. After making "connect",
    we wait for 5 seconds for application to get connected with device.
    Problem we're facing is that last device (10th) is online but we got
    it as offline. Reason- till the last moment of wait "connect" has not
    sent the connection request to device. After the 5 seconds device is
    receiving the connection request. As as solution we can-

    1. increase the wait time
    2. submit the job only in 7-8 threads at a time.
    3.  combination of above both

    But I'm just surprise on performance of socket API and wondering if
    we're missing the settings, which can helps to boost the performance.

    I'd appreciate any help. Please do let me know in case I need to give
    more information.

    Here is code we're using (it is legacy code)-

    int Connect_To_Port(SOCKET win_socket, char *host, unsigned short
    port, int connTimeout)
    {

     int    retval, err;
     SOCKADDR_IN  server;
     SOCKADDR_IN  client;
     unsigned long l;
     WSAEVENT  connEvent;

     memset(&server, 0, sizeof(server));
     server.sin_family  = AF_INET;
     server.sin_port   = htons(port);
     server.sin_addr.s_addr = htonl(INADDR_ANY);

     l = inet_addr(host);
     memset(&client, 0, sizeof(client));
     client.sin_family = AF_INET;
     client.sin_port = htons(port);
     memcpy(&(client.sin_addr),&l,4);

     char szBuf[MAX_PATH];
     memset(szBuf,0,sizeof(szBuf));

     if (connTimeout > 0 && connTimeout < 180000)
     {
      // Mark our socket non-blocking, and ask for asynch notifications.
      connEvent = WSACreateEvent();
      if(WSAEventSelect(win_socket,connEvent,FD_CONNECT) == SOCKET_ERROR)
      {
          return BII_ERR_OPENSOCKET;
      }
     }

     DWORD dwStatus = 0;
     timeval readTimeout;
     fd_set fs;

     // connect to remote host
      retval = connect(win_socket,(sockaddr*)&client,sizeof(client));
     if (retval == SOCKET_ERROR)
     {
      err = WSAGetLastError();
      switch (err)
      {
       case (WSAEISCONN):   // already connected! no problem man

        return TRUE;
       case (WSAEWOULDBLOCK):     // not ready yet...return so that we
    don't block
        {

         DWORD dwStatus = 0;
         dwStatus = WSAWaitForMultipleEvents
    (1,&connEvent,FALSE,connTimeout,TRUE);

         if(dwStatus == WSA_WAIT_EVENT_0)
         {
          WSANETWORKEVENTS lpNetEvents;
          WSAEnumNetworkEvents(win_socket,connEvent,&lpNetEvents);
          if((lpNetEvents.lNetworkEvents & FD_CONNECT) &&
    (lpNetEvents.iErrorCode[FD_CONNECT_BIT] == 0))
          {

           return TRUE;
          }
          else
          {

           return BII_ERR_OPENSOCKET;
          }
         }
         else
         {

          return BII_ERR_OPENSOCKET;
         }
        }
       default:

        return BII_ERR_OPENSOCKET; // real error
      }
     }
     return TRUE;

    quarta-feira, 18 de fevereiro de 2009 12:34