public void registerNetworkService() throws Exception {
  chatServer = new ChatServer(this);
  ServerSocket serverSocket = chatServer.getServerSocket();
  if (serverSocket == null) {
    throw new Exception("Could not get server socket");
  }
  chatServer.start();
  
  ServiceInfo serviceInfo = ServiceInfo.create(
    Constants.SERVICE_TYPE,
    Constants.SERVICE_NAME,
    port,
    Constants.SERVICE_DESCRIPTION
  );
  
  if (jmDns != null && serviceInfo != null) {
    serviceName = serviceInfo.getName();
    jmDns.registerService(serviceInfo);
  }
}

public void unregisterNetworkService() {
  if (jmDns != null) {
    jmDns.unregisterAllServices();
  }	
  
  chatServer.stopThread();
  
  // ...
}