昨天回忆了一下以前做的一个实时的群聊小程序。用JAVA写得。开发步骤如下：
这是面向过程的开发。
第一步，建立服务器端。
第二步，建立客户端并连接服务端。
第三步，客户端发送消息服务器端能接收到。
第四步，实现多客户连接服务端，并能接收多客户端发来的消息。可以采用多线程和异步的方法解决服务端被占用的情况。
第五步，服务端转发客户端发送的信息到每一个客户端。
第六步，消除小Bug。
ChatServer.java
import java.io.DataInputStream;import java.io.DataOutputStream;import java.io.EOFException;import java.util.*;import java.io.IOException;import java.net.BindException;import java.net.ServerSocket;import java.net.Socket;import java.net.SocketException;public class ChatServer{ boolean started = false; ServerSocket ss = null; List clients = new ArrayList (); public static void main(String[] args) { new ChatServer().start(); } public void start(){ try { ss = new ServerSocket(8881); } catch (BindException e){ System.out.println("端口已被占用！"); System.out.println("请结束相关进程！"); System.exit(0); } catch (Exception e) { e.printStackTrace(); } try{ started = true; while (started) { Socket s = ss.accept(); //阻塞性函数，不断接收客户端连接 Client c = new Client(s);//不能再静态main()里面new一个动态的方法,故将启动过程包装成一个public函数System.out.println("a client connected"); new Thread(c).start(); clients.add(c); } } catch (Exception e) { e.printStackTrace(); }finally{ try { ss.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } class Client implements Runnable{//区分客户端，用一个线程操作一个客户端，也可以采用异步的方法。这里用线程，比较占资源。等我写出异步的方法后再共享。 private Socket s= null; private DataInputStream dis= null; private DataOutputStream dos=null; private boolean bConnected = false; public Client(Socket s){ this.s= s; try { dis=new DataInputStream(s.getInputStream()); dos=new DataOutputStream(s.getOutputStream()); bConnected = true; } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public void send(String str){ // try { dos.writeUTF(str); } catch (IOException e) { // TODO Auto-generated catch block clients.remove(this); System.out.println("一个客户退出了！List已去除"); //e.printStackTrace(); } } public void run() { try { while (bConnected) { String str; str = dis.readUTF();// 阻塞性函数，会一直占用线程资源System.out.println(str); for (int i = 0; i < clients.size(); i++) { Client c = clients.get(i); c.send(str); } } } catch (EOFException e){ System.out.println("一个客户已退出！"); }catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ if(dis!=null) try { dis.close(); if (dos != null) dos.close(); if (s != null) s.close(); } catch (SocketException e) { clients.remove(this); System.out.println("一个客户已退出！"); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }} ChatClient.java
import java.awt.BorderLayout;import java.awt.Frame;import java.awt.TextArea;import java.awt.TextField;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.event.WindowAdapter;import java.awt.event.WindowEvent;import java.io.DataInputStream;import java.io.DataOutputStream;import java.io.EOFException;import java.io.IOException;import java.net.Socket;import java.net.SocketException;import java.net.UnknownHostException; public class ChatClient extends Frame{ Socket s = null; DataOutputStream dos = null; DataInputStream dis = null; private boolean bConnected=false; TextField tfTxt = new TextField();//输入框 TextArea taContent = new TextArea();//显示聊天信息框 public static void main(String[] args) { new ChatClient().lanunchFrame(); } public void lanunchFrame(){ setLocation(400,300); this.setSize(300, 300); add(tfTxt,BorderLayout.SOUTH); add(taContent,BorderLayout.NORTH); pack();//调整空隙 this.addWindowListener(new WindowAdapter(){ @Override public void windowClosing(WindowEvent e) { disconnect(); System.exit(0); } }); tfTxt.addActionListener(new TexFileListener()); setVisible(true); connect(); new Thread(new RecvThread()).start(); } public void connect(){ try { s= new Socket("127.0.0.1",8881); dos=new DataOutputStream(s.getOutputStream()); dis=new DataInputStream(s.getInputStream());System.out.println("connected!"); bConnected =true; } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } public void disconnect() { try { dos.close(); dis.close(); s.close(); } catch (Exception e1) { e1.printStackTrace(); } /*try { bConnected = false; //保证 recvThread.join(); } catch (InterruptedException e){ e.printStackTrace(); } finally{ try { dos.close(); dis.close(); s.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } }*/ } private class TexFileListener implements ActionListener{ public void actionPerformed(ActionEvent e) { String str=tfTxt.getText().trim(); //taContent.setText(str); tfTxt.setText(""); try { dos.writeUTF(str); dos.flush(); //dos.close(); } catch (IOException e1) { e1.printStackTrace(); } } } private class RecvThread implements Runnable{ public void run() { try { while (bConnected) { String str = dis.readUTF(); //System.out.println(str); taContent.setText(taContent.getText()+str+'\n'); } } catch (SocketException e){ System.out.println("已退出！"); } catch (EOFException e){ System.out.println("已退出！"); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }}