Flip a coin endlessly v2 - StopListener

package com.rmb.randomnodatabase.taskmanagement;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * Listen for stop signal and set {@link #isActive()} to false.
 *
 * See: http://bit.ly/1oKSnHu
 *
 */
public final class StopListener extends Thread {

   /** Default port to listen to. */
   public static final int DEFAULT_PORT = 7;

   /** Default stop signal. */
   public static final String STOP_SIGNAL = "stop signal sent";

   /** Port to listen at. */
   private final int port;

   /** True until stop signal is received. */
   private boolean active = true;

   /**
    * Record incoming message here, if something other than STOP comes through.
    */
   private final StringBuilder message;

   /**
    * Create listener with custom port.
    *
    * @param thePort
    *           port to listen at
    */
   public StopListener(final int thePort) {
      port = thePort;
      message = new StringBuilder();
   }

   /**
    * Create listener with default port.
    */
   public StopListener() {
      this(DEFAULT_PORT);
   }

   @Override
   public void run() {
      try (ServerSocket serverSocket = new ServerSocket(port);
            Socket clientSocket = serverSocket.accept();
            PrintWriter out =
                  new PrintWriter(clientSocket.getOutputStream(), true);
            BufferedReader in =
                  new BufferedReader(new InputStreamReader(
                        clientSocket.getInputStream()));) {
         String inputLine;
         while ((inputLine = in.readLine()) != null) {
            message.append(inputLine);
            out.println("Stop signal received.");
            active = false;
            break;
         }
      } catch (IOException e) {
         System.out.println("Exception caught when trying to listen on port ["
               + port + "] or listening for a connection");
         System.out.println(e.getMessage());
      }
   }

   /**
    * @return true until stop signal is received. False when stop signal was
    *         received.
    */
   public boolean isActive() {
      return active;
   }

   /**
    * @return message delivered to this listener by client.
    */
   public String getMessage() {
      return message.toString();
   }

   /**
    * Test listener.
    *
    * @param args
    *           not used.
    */
   public static void main(final String[] args) {
      StopListener listener = new StopListener();
      System.out.println("Listening now - listener.isActive() ["
            + listener.isActive() + "].");
      listener.start();
      try {
         listener.join();
      } catch (InterruptedException e) {
         e.printStackTrace();
      }
      System.out.println("Stopped - listener.isActive() ["
            + listener.isActive() + "].");
   }
}