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Server.javaAPI DocExample27134Mon Sep 22 13:30:32 BST 1997None

Server

public class Server extends Object
This class is a generic framework for a flexible, multi-threaded server. It listens on any number of specified ports, and, when it receives a connection on a port, passes input and output streams to a specified Service object which provides the actual service. It can limit the number of concurrent connections, and logs activity to a specified stream.

Fields Summary
ConnectionManager
connectionManager
Hashtable
services
ThreadGroup
threadGroup
PrintWriter
logStream
Constructors Summary
public Server(OutputStream logStream, int maxConnections)
This is the Server() constructor. It must be passed a stream to send log output to (may be null), and the limit on the number of concurrent connections. It creates and starts a ConnectionManager thread which enforces this limit on connections.

 
    setLogStream(logStream);
    log("Starting server");
    threadGroup = new ThreadGroup("Server");
    connectionManager = new ConnectionManager(threadGroup, maxConnections);
    connectionManager.start();
    services = new Hashtable();
Methods Summary
public voidaddService(Server$Service service, int port)
This method makes the server start providing a new service. It runs the specified Service object on the specified port.

    Integer key = new Integer(port);  // the hashtable key
    // Check whether a service is already on that port
    if (services.get(key) != null) 
      throw new IllegalArgumentException("Port " + port + " already in use.");
    // Create a Listener object to listen for connections on the port
    Listener listener = new Listener(threadGroup, port, service);
    // Store it in the hashtable
    services.put(key, listener);
    // Log it
    log("Starting service " + service.getClass().getName() + 
        " on port " + port);
    // Start the listener running.
    listener.start();
protected synchronized voidlog(java.lang.String s)
Write the specified string to the log

 
    if (logStream != null) {
      logStream.println("[" + new Date() + "] " + s);
      logStream.flush();
    }
protected voidlog(java.lang.Object o)
Write the specified object to the log

 log(o.toString());
public static voidmain(java.lang.String[] args)
A main() method for running the server as a standalone program. The command-line arguments to the program should be pairs of servicenames and port numbers. For each pair, the program will dynamically load the named Service class, instantiate it, and tell the server to provide that Service on the specified port. The special -control argument should be followed by a password and port, and will start special server control service running on the specified port, protected by the specified password.

    try {
      if (args.length < 2)  // Check number of arguments
        throw new IllegalArgumentException("Must start at least one service");
      
      // Create a Server object that uses standard out as its log and
      // has a limit of ten concurrent connections at once.
      Server s = new Server(System.out, 10);

      // Parse the argument list
      int i = 0;
      while(i < args.length) {
        if (args[i].equals("-control")) {    // Handle the -control argument
          i++;
          String password = args[i++];
          int port = Integer.parseInt(args[i++]);
          s.addService(new Control(s, password), port);  // add control service
        } 
        else {
          // Otherwise start a named service on the specified port.
          // Dynamically load and instantiate a class that implements Service.
          String serviceName = args[i++];
          Class serviceClass = Class.forName(serviceName); // dynamic load
          Service service = (Service)serviceClass.newInstance(); // instantiate
          int port = Integer.parseInt(args[i++]);
          s.addService(service, port);
        }
      }
    }
    catch (Exception e) { // Display a message if anything goes wrong
      System.err.println("Server: " + e);
      System.err.println("Usage: java Server [-control <password> <port>] " +
                         "[<servicename> <port> ... ]");
      System.exit(1);
    }
public voidremoveService(int port)
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

    Integer key = new Integer(port);  // hashtable key
    // Look up the Listener object for the port in the hashtable of services
    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);
public voidsetLogStream(java.io.OutputStream out)
A public method to set the current logging stream. Pass null to turn logging off

    if (out != null) logStream = new PrintWriter(new OutputStreamWriter(out));
    else logStream = null;