网络聊天实现步骤（从功能谈论方法）：
客户端：
1.登录面板：注册提醒用户注册格式，登录账号密码不为空，点击登录的时候需要连接服务器端，启动聊天面板。（监听用户点击登录，这时候连接服务器）
2.聊天面板：消息框接收服务器端发送的消息，发送消息框保存消息内容，点击发送按钮将发送消息框递给服务器端（需要创造一个线程不断监听服务器端发送回来的消息，并且显示在消息框）
服务器端：
1.服务器端需要循环监听客户端发送过来的连接
2.把循环接收到的多个客户端用集合储存起来
3.为每个客户端建立一个线程，用来接收他们发送的消息并且为其他客户端转送消息。
4.发送公告功能：聊天面板，发送公告面板，发送按钮（将发送面板的消息发送给各个客户端）。
客户端启动界面
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.net.Socket;public class Logon extends JFrame {public Logon() {this.setTitle("欢迎登录");this.setSize(400, 400);this.setLocationRelativeTo(null);this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//标签JLabel jLabel = new JLabel("欢迎登录");jLabel.setFont(new Font("楷体", Font.BOLD, 20));//字体jLabel.setForeground(new Color(21, 12, 12));JPanel jPanel = new JPanel();jPanel.add(jLabel);//账号JPanel jPanel1 = new JPanel();JLabel jLabel1 = new JLabel("账号");JTextField jTextField1 = new JTextField(15);jPanel1.add(jLabel1);jPanel1.add(jTextField1);//密码JPanel jPanel2 = new JPanel();JLabel jLabel2 = new JLabel("密码");JTextField jTextField2 = new JTextField(15);jPanel2.add(jLabel2);jPanel2.add(jTextField2);//按钮//登录JButton jButton = new JButton("登录");jButton.addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {if (jTextField1.getText().equals("") || jTextField2.getText().equals("")) {JOptionPane.showMessageDialog(null, "请输入");} else {try {Socket socket = new Socket("192.168.124.89", 9999);new ChatMap(jTextField1.getText(),socket);dispose();} catch (IOException ioException) {ioException.printStackTrace();JOptionPane.showMessageDialog(null, "没有连接至服务器，请稍后");}}}});//注册JButton jButton1 = new JButton("注册");jButton1.addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {if (!jTextField1.getText().matches("\\w*") || !jTextField2.getText().matches("\\w*")) {JOptionPane.showMessageDialog(null, "只支持大小写字母及数字");}}});JPanel jPanel3 = new JPanel();jPanel3.add(jButton);jPanel3.add(jButton1);this.setLayout(new GridLayout(4, 1));this.add(jPanel);this.add(jPanel1);this.add(jPanel2);this.add(jPanel3);this.setVisible(true);//让窗口显示,放在代码的最后一行。}
}
客户端聊天界面
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.text.SimpleDateFormat;
import java.util.Date;public class ChatMap extends JFrame {JTextArea jTextArea;public ChatMap(String account, Socket socket) throws IOException {//向服务器发送信息DataOutputStream dataOutputStream=new DataOutputStream(socket.getOutputStream());this.setTitle("欢迎来到"+account+"聊天室");this.setSize(400, 400);this.setLocationRelativeTo(null);this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//创造面版JPanel jPanel = new JPanel(new BorderLayout());//聊天窗口jTextArea = new JTextArea(20, 15);jTextArea.setEnabled(false);jTextArea.setLineWrap(true);JScrollPane jScrollPane = new JScrollPane(jTextArea);jPanel.add(jScrollPane,BorderLayout.NORTH);//输入窗口JTextArea jTextArea1 = new JTextArea(1, 10);jTextArea.setLineWrap(true);JScrollPane jScrollPane1 = new JScrollPane(jTextArea1);jPanel.add(jScrollPane1,BorderLayout.CENTER);//按钮JButton jButton=new JButton("发送");jButton.addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {String message=jTextArea1.getText();if(message.length()==0)//为什么要依靠message长度判断{JOptionPane.showMessageDialog(null, "输入不能为空");return;}//不为空显示日期向服务器发送信息Date date=new Date();SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");String str=sdf.format(date);String msg=account+":"+str+"\n";msg+=message;try {dataOutputStream.writeUTF(msg);//发送消息jTextArea1.setText("");//清空发送框} catch (IOException ioException) {ioException.printStackTrace();JOptionPane.showMessageDialog(null, "内容发送失败，请检查网络");}}});jPanel.add(jButton,BorderLayout.EAST);this.add(jPanel);this.setVisible(true);//让窗口显示,放在代码的最后一行。//面板创造完毕建立监听（服务器传入的消息）new BThread(socket,jTextArea).start();}//内部类监听服务器端class BThread extends Thread{DataInputStream dataInputStream;public BThread(Socket socket,JTextArea jTextArea) throws IOException {dataInputStream=new DataInputStream(socket.getInputStream());}@Overridepublic void run() {while(true)//循环条件：退出{try {String message=dataInputStream.readUTF();jTextArea.append(message+"\n");} catch (IOException e) {e.printStackTrace();System.out.println("服务器断开连接");break;//停止客户端线程}}}}} 
启动客户端
public class Run {public static void main(String[] args) {new Logon();}
}服务器端界面
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;public class server extends JFrame {ArrayList<Socket> sockets=new ArrayList<>();Socket socket;JTextArea jTextArea;JTextArea jTextArea1;JButton jButton;public server(){//设置窗口this.setTitle("服务器");this.setSize(400, 400);this.setLocationRelativeTo(null);this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);JPanel jPanel=new JPanel(new BorderLayout());jTextArea=new JTextArea();jTextArea.setEnabled(false);//不可进行操作jTextArea.setLineWrap(true);JScrollPane jScrollPane=new JScrollPane(jTextArea);//发送JPanel jPanel1=new JPanel();jTextArea1=new JTextArea();jTextArea1.setEnabled(true);//可进行操作jTextArea1.setLineWrap(true);JScrollPane jScrollPane1=new JScrollPane(jTextArea1);jButton=new JButton("发送");jButton.addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {String massage=jTextArea1.getText();for (Socket s:sockets){DataOutputStream dOut= null;try {dOut = new DataOutputStream(s.getOutputStream());dOut.writeUTF("公告："+massage);} catch (IOException ioException) {ioException.printStackTrace();JOptionPane.showMessageDialog(null, "发送失败");}}}});jPanel1.add(jScrollPane1);jPanel1.add(jButton);jPanel.add(jScrollPane);jPanel.add(jPanel1,BorderLayout.SOUTH);this.add(jPanel);this.setVisible(true);//启动服务器this.startServer();}public void startServer(){try {ServerSocket serverSocket=new ServerSocket(9999);while(true){socket= serverSocket.accept();//阻塞程序System.out.println("服务器启动成功");sockets.add(socket);System.out.println("有客户端连接上了，客户端连接数为："+sockets.size());//为每一个连接到服务器的客户端开启一个线程new A(socket).start();}} catch (IOException e) {e.printStackTrace();System.out.println("启动服务器失败");}}//创造一个内部类监听各个客户端是否给服务器端发送消息class A extends Thread{DataInputStream dataInputStream;public A(Socket socket) throws IOException {dataInputStream=new DataInputStream(socket.getInputStream());}@Overridepublic void run() {while (true){//一直厮混换,监听客户端发送的消息try {String msg=dataInputStream.readUTF();jTextArea.append(msg+"\n");//向不同的客户端转发消息for(Socket s:sockets){DataOutputStream dOut=new DataOutputStream(s.getOutputStream());dOut.writeUTF(msg);}} catch (IOException e) {e.printStackTrace();System.out.println("一位客户端下线了");sockets.remove(socket);break;}}}}
}
启动服务器
public class serverRun {public static void main(String[] args) {new server();}
}
