routerthread.java

使用Java语言编写模拟路由器程序

/* File: RouterThread.java
 * 
 * This file contains the code for the class RouterThread,
 * which represents the thread spawned by each Router to
 * listen for Distance Vectors from other Routers
 */

import java.io.*;
import java.net.*;

class RouterThread extends Thread {
	// The Router that spawned this thread
	Router r;

	// The port on which this thread listens for Distance Vector packets
	int port;

	/*
	 * Constructor
	 * 
	 * @r: the instance of the Router that spawned this thread @port: the port
	 * number
	 */
	public RouterThread(Router r, int port,String threadName) {
		// create a new thread
		super(threadName);

		this.r = r;
		this.port = port;

		// start the thread
		start();
	}

	/*
	 * Method Name: run
	 * 
	 * Use: To start the execution of the thread
	 */
	public void run() {
		// The socket used to listen on the port
		ServerSocket l = null;

		// The socket for representing accepted connection
		Socket t;

		// The input stream associated with the connection
		ObjectInputStream ois;

		try {
			// listen on the port
			l = new ServerSocket(port);
			System.out
					.println("Router "+Thread.currentThread().getName()+": Listening for neighbors' updates on port "
							+ port);
		} catch (Exception e) {
			System.out
					.println("Router "+Thread.currentThread().getName()+": Unable to open a listening socket on port: "
							+ port);
			System.out.println("Quitting.");
			System.exit(1);
		}

		while (true) {
			try {
				// accept a connection
				t = l.accept();
			} catch (Exception e) {
				System.out.println("Router "+Thread.currentThread().getName()+" :"+e.getMessage());
				e.printStackTrace();
				System.out
						.println("Router "+Thread.currentThread().getName()+": An I/O error occired while accepting a connection");
				continue;
			}

			try {
				// open the input stream
				ois = new ObjectInputStream(t.getInputStream());

				// read the distance vector packet
				Packet p = (Packet) ois.readObject();

				// process the packet
				r.processDV(p);

				// close the stream and the connection
				ois.close();
				t.close();
			} catch (Exception e) {
				System.out.println("Router "+Thread.currentThread().getName()+" :"+e.getMessage());
				e.printStackTrace();
				System.out.println("Router "+Thread.currentThread().getName()+": An I/O error occured while communicating");
				continue;
			}
		}
	}
}