用Java发送和接收套接字消息

Question

We're doing a socket programming project for our Uni. We are developing a file sync software, and we're currently stuck with sending and receiving messages sent over socket.

So, when testing on local machine, code works perfectly. But, when we simulate the server-client environment over LAN and WiFi we get null pointer exception. The files are being sent in chunks so only 5-10 of them pass through.

I guess there is some issue regarding the total time needed for sending messages over socket, and that this is the reason why we get the exception.

Method for sending messages sends the message and starts the timer thread. If no answer is received from the server within 2 seconds, the message will be sent again. Here is the code for sending messages:

public static void sendMessage(final byte[] message) {
  try {
    final Thread timer = new Thread() {                
      @Override
      public void run() {
        try {
          System.out.println("timer started");
          sleep(1500);
          System.out.println("timer timeout");
          sendMessage(message);
        } catch (Exception e) {
          e.printStackTrace();
        }
      }
    };

    Thread thread = new Thread() {
      @Override
      public void run() {
        try {
          byte[] buffer = new byte[1250];
          serverByteStream.read(buffer);
          timer.stop();
        } catch (Exception e) {
        }
      }
    };

    timer.start();
    serverByteStream.write(message);
    thread.start();
  } catch (Exception e) {   
  }
}

Answer 1

When you recursively call sendMessage() again, you should kill the thread thread also.

Please post the full stacktrace and code where the error occurs also.