Question

I have to write java codes implementing the TCP server & TCP client with a 10% of transmission failure determined by a random number. Now in the receiver side it needs to wait for 2000 ms(2 sec.) & if no data received from the sender in this 2 sec. then it will stop waiting for data from the sender & send back a negative ACK to the sender.

BufferedReader inFromSender =new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
        long startTime = System.currentTimeMillis();
        while(( System.currentTimeMillis() - startTime) < 2000 )
        {
            clientSentence = inFromSender.readLine();
            System.out.println("Received: " + clientSentence);
        }
        System.out.println("Data Transmission failed");

But once the while loop begins & the receiver goes in to read from the sender, it never breaks.. even if the 2 sec. timeout is over. How can I abort/stop the receiver from waiting for sender data after 2 sec (timeout).

Answer 1

One way to go would be to have a Thread that would close the socket when the timeout is reached. This would make the read(...) call fail (probably an IOException) and therefore you would go out from the loop.

Example:

final Socket connectionSocket = new Socket("...", 8888); // To be changed
BufferedReader inFromSender = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
Thread t = new Thread() {
   public void run() {
      try {
          Thread.sleep(2000); // Wait 2 s
          connectionSocket.close();
          System.out.println("Data Transmission failed");
      } catch(InterruptedException e) {
         // Handle exception
      }
   }
};
t.start();
while((clientSentence = inFromSender.readLine()) != null) {
   System.out.println("Received: " + clientSentence);
}