前言
前几天没什么事儿，在学习UDP和TCP传输协议，顺手做了一个基于UDP协议的聊天小程序，同时复习了Java的GUI知识。程序运行截图展示
1.运行程序，生成第一个窗口，输入要监听的端口号:1234(示例端口号）
2.再次运行程序，生成第二个聊天窗口，并且要输入端口号：4321（示例端口号）
3.然后，两个聊天窗口之间便可以对话了。
3.程序代码解读
首先，贴上全部代码，稍后会慢慢解释每一部分。/**
*
*/
package com.bert.udp;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.SocketException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
/**
* @author Bert
* 2019.03.09
*/
public class GuiChat extends JFrame {
private static final int DEFAULT_PORT = 8899;
//把主窗口分为 NORTH.CENTER.SOUTH 三部分
private JLabel stateLB; //显示监听状态
private JTextArea centerTextArea; //显示聊天记录
private JPanel sourthPanel; //最下面的面板
private JTextArea inputTextArea; //聊天输入框
private JPanel bottomPanel; //放置IP输入框，按钮等
private JTextField ipTextField; //IP输入框
private JTextField remotePortTF; //端口号输入框
private JButton sendBT; //发送按钮
private JButton clearBT; //清除按钮
private DatagramSocket datagramSocket; //发送数据用的载体
/*
* 在构造方法中完成界面初始化，Socket连接初始化，和建立监听状态
*/
public GuiChat() {
setUPUI();
initSocket();
setListener();
}
/*
* 在 main方法中创建一个GuiChat类的对象，便是运行了程序；
*/
public static void main(String [] args) {
new GuiChat();
}
/*
* 初始化聊天界面
*/
private void setUPUI() { //聊天页面初始化
setTitle("GUI聊天程序---出自JaffyMore"); //窗口标题栏设置
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //窗口关闭时触发动作：退出程序
setSize(400, 400); //窗口默认尺寸设置
setResizable(false); //窗口大小不允许改动
setLocationRelativeTo(null); //窗口居中
//设置窗口中的North部分
stateLB = new JLabel("当前还未启动监听");
stateLB.setHorizontalAlignment(JLabel.RIGHT);
//窗口中的Center部分
centerTextArea = new JTextArea();
centerTextArea.setEditable(false);
centerTextArea.setBackground(new Color(211, 211, 211));
//窗口中的South部分
sourthPanel = new JPanel(new BorderLayout());
inputTextArea = new JTextArea(5,20);
bottomPanel = new JPanel(new FlowLayout(FlowLayout.CENTER,5,5));
ipTextField = new JTextField("127.0.0.1",8);
remotePortTF = new JTextField(String.valueOf(DEFAULT_PORT),3);
sendBT =new JButton("发送");
clearBT = new JButton("清屏");
bottomPanel.add(ipTextField);
bottomPanel.add(remotePortTF);
bottomPanel.add(sendBT);
bottomPanel.add(clearBT);
sourthPanel.add(new JScrollPane(inputTextArea),BorderLayout.CENTER);
sourthPanel.add(bottomPanel,BorderLayout.SOUTH);
add(stateLB,BorderLayout.NORTH);
add(new JScrollPane(centerTextArea), BorderLayout.CENTER);
add(sourthPanel, BorderLayout.SOUTH);
setVisible(true);
}
private void setListener() {//为按钮添加监听事件
sendBT.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
//获取发送的目标IP和端口号
final String ipAddress = ipTextField.getText();
final String remotePort = remotePortTF.getText();
//判断IP地址和端口号是否为空
if(ipAddress == null ||ipAddress.trim().equals("")
||remotePort == null || remotePort.trim().equals("")){
JOptionPane.showMessageDialog(GuiChat.this, "请输入IP地址和端口号");
return;
}
if(datagramSocket == null || datagramSocket.isClosed()) {
JOptionPane.showMessageDialog(GuiChat.this, "监听不成功");
return;
}
//获取需要发送的内容
String sendContent = inputTextArea.getText();
byte[] buf = sendContent.getBytes();
try {
//将发送的内容显示到自己的聊天记录中
centerTextArea.append("我对" + ipAddress + ":" +
remotePort + "说 \n" + inputTextArea.getText() +"\n\n" );
//添加内容后，使滚动条自动滚动到最低端
centerTextArea.setCaretPosition(centerTextArea.getText().length());
//发送数据
DatagramPacket packet = new DatagramPacket(buf,buf.length,
InetAddress.getByName(ipAddress),Integer.parseInt(remotePort));
datagramSocket.send(packet);
inputTextArea.setText("");
}catch(IOException e1) {
JOptionPane.showMessageDialog(GuiChat.this, "出错了，本次发送失败");
e1.printStackTrace();
}
}
});
//为ClearBT 按钮添加事件监听器
clearBT.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
centerTextArea.setText("当前聊天内容为空，哈哈哈");
}
});
}
private void initSocket() {
int port = DEFAULT_PORT;
while(true) {
try {
if(datagramSocket != null && !datagramSocket.isClosed()) {
datagramSocket.close();
}
try {
//判断端口号范围
port = Integer.parseInt(JOptionPane.showInputDialog(this,
"请输入端口号","端口号",JOptionPane.QUESTION_MESSAGE));
if(port <1 || port >65535) {
throw new RuntimeException("端口号超出范围" + port);
}
}catch(Exception e) {
JOptionPane.showMessageDialog(null, "你输入的端口号不正确" );
continue;
}
//启动DataGramSocket
datagramSocket = new DatagramSocket(port);
startListen();
stateLB.setText("正在监听端口号：" + port);
break;
}catch(SocketException e) {
JOptionPane.showMessageDialog(this, "端口号已经被占用，请重新输入" );
stateLB.setText("当前还未启动监听");
}
}
}
private void startListen() { //创建线程进行消息接收
new Thread() {
private DatagramPacket datagramPacket;
public void run() {
byte [] buf = new byte[1024];
//创建数据包
datagramPacket = new DatagramPacket(buf, buf.length);
while(!datagramSocket.isClosed()) {
try {
datagramSocket.receive(datagramPacket);
centerTextArea.append(datagramPacket.getAddress().getHostAddress()
+ ":" + ((InetSocketAddress) datagramPacket.getSocketAddress()
).getPort() +"对我说： \n" + new String(datagramPacket.getData(),0,datagramPacket.getLength())
+"\n\n" );
}catch(IOException e) {
e.printStackTrace();
}
}
}
}.start();
}
}