Networking - Java Examples in a Nutshell - page 105

Example 5•9: Server.java (continued)
/**
* This method makes the server stop providing a service on a port.
* It does not terminate any pending connections to that service, merely
* causes the server to stop accepting new connections
**/
public synchronized void removeService(int port) {
Integer key = new Integer(port); // hashtable key
// Look up the Listener object for the port in the hashtable
final Listener listener = (Listener) services.get(key);
if (listener == null) return;
// Ask the listener to stop
listener.pleaseStop();
// Remove it from the hashtable
services.remove(key);
// And log it.
log("Stopping service " + listener.service.getClass().getName() +
" on port " + port);
}
/**
* This nested Thread subclass is a "listener". It listens for
* connections on a specified port (using a ServerSocket) and when it gets
* a connection request, it calls the servers addConnection() method to
* accept (or reject) the connection. There is one Listener for each
* Service being provided by the Server.
**/
public class Listener extends Thread {
ServerSocket listen_socket; // The socket to listen for connections
int port; // The port we're listening on
Service service; // The service to provide on that port
volatile boolean stop = false; // Whether we've been asked to stop
/**
* The Listener constructor creates a thread for itself in the
* threadgroup. It creates a ServerSocket to listen for connections
* on the specified port. It arranges for the ServerSocket to be
* interruptible, so that services can be removed from the server.
**/
public Listener(ThreadGroup group, int port, Service service)
throws IOException
{
super(group, "Listener:" + port);
listen_socket = new ServerSocket(port);
// give it a non-zero timeout so accept() can be interrupted
listen_socket.setSoTimeout(600000);
this.port = port;
this.service = service;
}
/**
* This is the polite way to get a Listener to stop accepting
* connections
***/
public void pleaseStop() {
this.stop = true; // Set the stop flag
this.interrupt(); // Stop blocking in accept()
try { listen_socket.close(); } // Stop listening.
catch(IOException e) {}