chatserver.java

简易的局域网聊天工具

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

public class ChatServer {

	boolean started = false;

	ServerSocket ss = null;

	List clients = new ArrayList();

	public void start() {

		try {
			ss = new ServerSocket(8888);
			started = true;
		} catch (BindException e) {
			// 检测到已经有服务端在运行时，要及时地推出，否则会继续执行下面的代码
			System.out.println("端口使用中......!");
			System.out.println("请关掉相关程序并重新运行服务器");
			System.exit(0);
		} catch (IOException e) {
			e.printStackTrace();
		}

		try {// 主线程负责接收客户端的链接

			while (started) {
				boolean bConnected = false;
				Socket s = ss.accept();
				// 当接收到客户端的链接后，各个客户启动自己的一个线程
				Client c = new Client(s);
				System.out.println("a client connected!");
				new Thread(c).start();
				clients.add(c);
			}

		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				// if(ss != null)
				ss.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	// 代表的是客户端在服务器端的一个包装
	class Client implements Runnable {
		// 每个客服都要有自己的链接
		private Socket s;

		private DataInputStream dis = null;

		private DataOutputStream dos = null;

		private boolean bConnected = true;

		public Client(Socket s) {
			this.s = s;
			try {
				dis = new DataInputStream(s.getInputStream());
				dos = new DataOutputStream(s.getOutputStream());
				// 一旦连上了，就设置为true，开始服务，不停的读
				bConnected = true;
			} catch (IOException e) {
				e.printStackTrace();
			}
		}

		public void send(String str) {
			
			try {
				dos.writeUTF(str);
			} catch (IOException e) {
				clients.remove(this);
				System.out.println("对方退出了，我从List里面退出了");
			}

		}

		public void run() {
			try {
				while (bConnected) {
					String str = dis.readUTF();
					System.out.println(str);
					// 只要一接收到每个client端的信息就马上转发给其他的client
					for (int i = 0; i < clients.size(); i++) {
						Client c = (Client) clients.get(i);
						c.send(str);
					}

					/*
					 * 下面的两个循环都可以代替上面的循环，但是程序内部会 for(Iterator it =
					 * clients.iterator();it.hasNext();) { Client c = (Client)
					 * it.next(); c.send(); }
					 */
					/*
					 * Iterator it = clients.iterator(); while(it.hasNext()) {
					 * Client c = (Client) it.next(); c.send(); }
					 */
				} 
			} catch (EOFException e) {
				System.out.println("Client Close!");
			} catch (Exception e) {
				e.printStackTrace();
			} finally {

				try {
					if (dis != null)
						dis.close();
					if (dos != null)
						dos.close();
					if (s != null)
						s.close();// 如果客户端断掉了，则要马上把Socket关掉，否则会出错
					// s = null;
				} catch (IOException e1) {
					e1.printStackTrace();
				}
				
			}
		}
	}

	public static void main(String[] args) {
		new ChatServer().start();
	}

}