java socket 之UDP编程
一、概念
在TCP的所有操作中都必须建立可靠的连接，这样一来肯定会浪费大量的系统性能，为了减少这种开销，在网络中又提供了另外的一种传输协议——UDP，不可靠的连接（这种协议在各种聊天工具中被广泛使用）。
在UDP程序的开发中使用DatagramPacket包装一条要发送的信息，之后使用DatagramSocket用于完成信息的发送操作。
例如：现在使用聊天工具进行聊天，那么A发送的信息B不一定能够接收的到，因为使用的就是UDP协议。
基于UDP通信的基本模式：
（1）将数据打包，称为数据包（好比将信件装入信封一样），然后将数据包发往目的地。
（2）接受别人发来的数据包（好比接收信封一样），然后查看数据包中的内容。
以下用一个聊天程序来说明，功能效果如下图所示：
二、工程目录
三、服务端
1）UDPServer类，服务端主类
import java.awt.event.ActionEvent;import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JTextField;
public class UDPServer extends JFrame implements ActionListener{
JTextArea jta;
JTextField jtf;
JButton jb;
JPanel jp;
ServerToClientThread stcT;
public static void main(String[] args) {
// TODO Auto-generated method stub
new UDPServer();
}
public UDPServer()
{
setTitle("UDP服务端");
jta=new JTextArea();
jtf=new JTextField(15);
jb=new JButton("发送");
jb.addActionListener(this);
jp=new JPanel();
jp.add(jtf);
jp.add(jb);
this.add(jta,"Center");
this.add(jp,"South");
this.setBounds(300, 200, 300, 200);
this.setVisible(true);
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
stcT = new ServerToClientThread(jta);
stcT.start();
/**窗体关闭按钮事件*/
this.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
if(JOptionPane.showConfirmDialog(null, "<html>确定退出吗？","系统提示",JOptionPane.OK_CANCEL_OPTION,JOptionPane.INFORMATION_MESSAGE)==0)
{
System.exit(0);
stcT.closeSocket();
}
else
{
return;
}
}
});
}
@Override
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
//假如点击了按钮jb
if(arg0.getSource()==jb)
{
byte buffer[] = jtf.getText().trim().getBytes();
stcT.sendData(buffer);
}
}
}
2）ServerToClientThread类，服务端处理线程
import java.net.DatagramPacket;import java.net.DatagramSocket;
import java.net.InetAddress;
import javax.swing.JTextArea;
/**
* @author lenovo
*
*/
public class ServerToClientThread extends Thread{
private String sendIP = "127.0.0.1";
private int sendPORT = 6666;
private int receivePORT = 8888;
//声明发送信息的数据报套结字
private DatagramSocket sendSocket = null;
//声明发送信息的数据包
private DatagramPacket sendPacket = null;
//声明接受信息的数据报套结字
private DatagramSocket receiveSocket = null;
//声明接受信息的数据报
private DatagramPacket receivePacket = null;
//缓冲数组的大小
public static final int BUFFER_SIZE = 5120;
private byte inBuf[] = null; //接收数据的缓冲数组
JTextArea jta;
// 构造函数
public ServerToClientThread(JTextArea jta) {
this.jta = jta;
}
public void run() {
try{
inBuf = new byte[BUFFER_SIZE];
receivePacket = new DatagramPacket(inBuf,inBuf.length);
receiveSocket = new DatagramSocket(receivePORT);
}catch (Exception e) {
e.printStackTrace();
// TODO: handle exception
}
while (true) {
if(receiveSocket == null){
break;
} else {
try {
receiveSocket.receive(receivePacket);
String message = new String(receivePacket.getData(),0,receivePacket.getLength());
jta.append("收到数据"+message+"\n");
} catch (Exception e) {
e.printStackTrace();
// TODO: handle exception
}
}
}
}
public void sendData(byte buffer[]){
try{
InetAddress address = InetAddress.getByName(sendIP);
// outBuf = new byte[BUFFER_SIZE];
sendPacket = new DatagramPacket(buffer,buffer.length,address,sendPORT);
sendSocket = new DatagramSocket();
sendSocket.send(sendPacket);
}catch (Exception e) {
e.printStackTrace();
// TODO: handle exception
}
}
public void closeSocket(){
receiveSocket.close();
}
}
三、客户端
1）UDPClient类，客户端主类
import java.awt.event.ActionEvent;import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JTextField;
public class UDPClient extends JFrame implements ActionListener{
JTextArea jta;
JTextField jtf;
JButton jb;
JPanel jp;
ClientToServerThread ctsT;
public static void main(String[] args) {
// TODO Auto-generated method stub
new UDPClient();
}
public UDPClient()
{
setTitle("UDP客户端");
jta=new JTextArea();
jtf=new JTextField(15);
jb=new JButton("发送");
jb.addActionListener(this);
jp=new JPanel();
jp.add(jtf);
jp.add(jb);
this.add(jta,"Center");
this.add(jp,"South");
this.setBounds(300, 200, 300, 200);
this.setVisible(true);
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
ctsT = new ClientToServerThread(jta);
ctsT.start();
/**窗体关闭按钮事件*/
this.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
if(JOptionPane.showConfirmDialog(null, "<html>确定退出吗？","系统提示",JOptionPane.OK_CANCEL_OPTION,JOptionPane.INFORMATION_MESSAGE)==0)
{
System.exit(0);
ctsT.closeSocket();
}
else
{
return;
}
}
});
}
@Override
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
//假如点击了按钮jb
if(arg0.getSource()==jb)
{
byte buffer[] = jtf.getText().trim().getBytes();
ctsT.sendData(buffer);
}
}
}
2）ClientToServerThread类，客户端线程处理类
import java.net.DatagramPacket;import java.net.DatagramSocket;
import java.net.InetAddress;
import javax.swing.JTextArea;
/**
* @author lenovo
*
*/
public class ClientToServerThread extends Thread{
private String sendIP = "127.0.0.1";
private int sendPORT = 8888;
private int receivePORT = 6666;
//声明发送信息的数据报套结字
private DatagramSocket sendSocket = null;
//声明发送信息的数据包
private DatagramPacket sendPacket = null;
//声明接受信息的数据报套结字
private DatagramSocket receiveSocket = null;
//声明接受信息的数据报
private DatagramPacket receivePacket = null;
//缓冲数组的大小
public static final int BUFFER_SIZE = 5120;
private byte inBuf[] = null; //接收数据的缓冲数组
JTextArea jta;
// 构造函数
public ClientToServerThread(JTextArea jta) {
this.jta = jta;
}
public void run() {
try{
inBuf = new byte[BUFFER_SIZE];
receivePacket = new DatagramPacket(inBuf,inBuf.length);
receiveSocket = new DatagramSocket(receivePORT);
}catch (Exception e) {
e.printStackTrace();
// TODO: handle exception
}
while (true) {
if(receiveSocket == null){
break;
} else {
try {
receiveSocket.receive(receivePacket);
String message = new String(receivePacket.getData(),0,receivePacket.getLength());
jta.append("收到数据"+message+"\n");
} catch (Exception e) {
e.printStackTrace();
// TODO: handle exception
}
}
}
}
public void sendData(byte buffer[]){
try{
InetAddress address = InetAddress.getByName(sendIP);
sendPacket = new DatagramPacket(buffer,buffer.length,address,sendPORT);
//注意发送的时候，socket不需要绑定地址
sendSocket = new DatagramSocket();
sendSocket.send(sendPacket);
}catch (Exception e) {
e.printStackTrace();
// TODO: handle exception
}
}
public void closeSocket(){
receiveSocket.close();
}
}
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