Problem with simple UDP client/server application

Ok. So I have a simple client program sending images over UDP to a specified IP address. At the specified IP a server program is listening and should receive the images.

When I try both programs on localhost (i.e. they are both running at 127.0.0.1) it works and the server receives the images. When I try to put the client and the server programs on different PCs in the same network it does not work.

147.232.24.163 is the server IP, 147.232.24.150 is the client IP.

Here is my client program:

  // Initialize UDP.    
  struct sockaddr_in server;    
  int n_sent;
  int socketId = socket(AF_INET, SOCK_DGRAM, 0);    
  if (socketId < 0)    
  {    
    cout << "Problem creating socket." << endl;    
  }    
  server.sin_family = AF_INET;    
  server.sin_addr.s_addr = inet_addr("147.232.24.163");    
  // Establish the server port numb开发者_JAVA百科er - we must use network byte order!    
  server.sin_port = htons(42001);

  for ( int iter = 0; iter < 60; iter++ )    
  {
      // load image into jpegBuf

      n_sent = sendto(socketId, reinterpret_cast<char*> (&jpegBuf[0]), jpegBuf.size(), 0, (struct sockaddr*) &server, sizeof(server));    
      if (n_sent < 0) {    
        cout << "Problem sending data." << endl;    
      }    
  }

  close(socketId);

Here is my server program:

int main()
{
    int bufferSize = 1024000;
    int iSockFd = -1;
    int iLength = 0;
    struct sockaddr_in servAddr, cliAddr;
    char buff[bufferSize];
    iSockFd=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    memset(&servAddr, 0, sizeof(servAddr));
    memset(&cliAddr, 0, sizeof(cliAddr));

    servAddr.sin_family = AF_INET;
    servAddr.sin_addr.s_addr = inet_addr("147.232.24.163"); 
    servAddr.sin_port = htons(42001);
    int cliAddrLen = sizeof(struct sockaddr_in);
    int bindRet = bind(iSockFd, (struct sockaddr*)&servAddr, sizeof(servAddr));
    cout << "Bind returned " << bindRet << endl;

    int i = 0;
    while (true)
    {
        int iRcvdBytes=recvfrom(iSockFd, buff, bufferSize, 0, 
        (struct sockaddr*)&cliAddr, (socklen_t*)&cliAddrLen);

        if (0 == i % 5)
        {
            cout << "Received " << iRcvdBytes << " bytes from the client" << endl;
        }


        i++;
    }
    close(iSockFd);
    return 0;
}

Any ideas why it does not work? I don't get any error messages.

This is not a solution but your code should be checking iRcvdbytes for error in the same way as the send code checks the result of sendto.

A return of 0 means the socket was closed gracefully (if connection-oriented - that should not apply here), SOCKET_ERROR means an error (in WinSock2 at least).

The socket on the send side needs to be created with IPPROTO_UDP, not 0. This could definitely be causing your failure.