java socket server, client detect server has died

Question

If I kill the Socket Server process, my Socket client process does not receive any errors, it continues to loop forever on the following code:

public void run() {
    while(readData) {
      String inputLine = null;
      try {
        while((inputLine = m_inputStream.readLine()) != null) {
          //do stuff
        }
      } catch (IOException e) {
         readData = false;
     }
  }
}

How can I detect that the socket server is gone and terminate the loop?

Answer 1

Terminate the outer loop when the call to readLine() returns null.

No exception is thrown when the server closes the connection normally. The stream should return null to signal the end of data.

This can be done with a loop like this:

public void run() {
  try {
    while (true) {
      String line = input.readLine();
      if (line == null)
        break;
      /* Process line. */
      ...
    }
  } catch (IOException ex) {
    /* Handle the exception as desired. */
    ex.printStackTrace();
  }
}

Answer 2

Whilst the answer from erickson is correct, have you tried setting the socket read time-out properties? (e.g. sun.net.client.defaultReadTimeout). If it is possible that the server may take a long time responding, then this might be less useful as a solution to your problem but is a good idea nevertheless in many scenarios.