java中DatagramPacket表示存放数据的数据报，DatagramSocket表示接受或发送数据报的套接字。
这两个类所有构成的网络链接是基于UDP协议的。
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
public class Sender {
public static void main(String[] args) {
try {
// 创建发送方的套接字，IP默认为本地，端口号随机
DatagramSocket sendSocket = new DatagramSocket();
// 确定要发送的消息：
String mes = "你好！接收方！";
// 由于数据报的数据是以字符数组传的形式存储的，所以传转数据
byte[] buf = mes.getBytes();
// 确定发送方的IP地址及端口号，地址为本地机器地址
int port = 8888;
InetAddress ip = InetAddress.getLocalHost();
// 创建发送类型的数据报：
DatagramPacket sendPacket = new DatagramPacket(buf, buf.length, ip, port);
// 通过套接字发送数据：
sendSocket.send(sendPacket);
// 确定接受反馈数据的缓冲存储器，即存储数据的字节数组
byte[] getBuf = new byte[1024];
// 创建接受类型的数据报
DatagramPacket getPacket = new DatagramPacket(getBuf, getBuf.length);
// 通过套接字接受数据
sendSocket.receive(getPacket);
// 解析反馈的消息，并打印
String backMes = new String(getBuf, 0, getPacket.getLength());
System.out.println("接受方返回的消息：" + backMes);
// 关闭套接字
sendSocket.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketAddress;
public class Receive {
public static void main(String[] args) {
try {
// 确定接受方的IP和端口号，IP地址为本地机器地址
InetAddress ip = InetAddress.getLocalHost();
int port = 8888;
// 创建接收方的套接字,并制定端口号和IP地址
DatagramSocket getSocket = new DatagramSocket(port, ip);
// 确定数据报接受的数据的数组大小
byte[] buf = new byte[1024];
// 创建接受类型的数据报，数据将存储在buf中
DatagramPacket getPacket = new DatagramPacket(buf, buf.length);
// 通过套接字接收数据
getSocket.receive(getPacket);
// 解析发送方传递的消息，并打印
String getMes = new String(buf, 0, getPacket.getLength());
System.out.println("对方发送的消息：" + getMes);
// 通过数据报得到发送方的IP和端口号，并打印
InetAddress sendIP = getPacket.getAddress();
int sendPort = getPacket.getPort();
System.out.println("对方的IP地址是：" + sendIP.getHostAddress());
System.out.println("对方的端口号是：" + sendPort);
// 通过数据报得到发送方的套接字地址
SocketAddress sendAddress = getPacket.getSocketAddress();
// 确定要反馈发送方的消息内容，并转换为字节数组
String feedback = "接收方说：我收到了！";
byte[] backBuf = feedback.getBytes();
// 创建发送类型的数据报
DatagramPacket sendPacket = new DatagramPacket(backBuf,
backBuf.length, sendAddress);
// 通过套接字发送数据
getSocket.send(sendPacket);
// 关闭套接字
getSocket.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
public class WC7 extends Frame implements ActionListener,Runnable
{
DatagramSocket D;
byte dataBuf[] = new byte[512];
InetAddress A;
DatagramPacket Pac = new DatagramPacket(dataBuf,dataBuf.length);
TextArea T1 = new TextArea();
TextField T2 = new TextField(23);
public WC7()
{
add(T1,"Center");
Panel P = new Panel();
P.add(new Label ("发送的信息"));
P.add(T2);
T2.addActionListener(this);
add(P,"South");
setSize(350,200);
setVisible(true);
setTitle("WC7");
addWindowListener (new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
(new Thread (this)).start();
}
public void actionPerformed(ActionEvent e1){
try {
String str = T2.getText();
byte[] buf = str.getBytes();
DatagramSocket D = new DatagramSocket();
InetAddress A = InetAddress.getLocalHost();
DatagramPacket P1 = new DatagramPacket (buf,buf.length,A,8002);
D.send(P1);
T2.setText("");
}
catch(Exception e2){
}
}
public void run()
{
try {
DatagramSocket D = new DatagramSocket(8001);
while(true)
{
D.receive(Pac);
String str = new String(Pac.getData(),0,Pac.getLength());
T1.append(Pac.getAddress()+" WC7说 "+str+"\n");
}
}
catch(Exception e3){
}
}
public static void main(String args[]){
new WC7();
}
}
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
public class WS7 extends Frame implements ActionListener,Runnable
{
DatagramSocket D;
byte dataBuf[] = new byte[512];
InetAddress A;
DatagramPacket Pac = new DatagramPacket(dataBuf,dataBuf.length);
TextArea T1 = new TextArea();
TextField T2 = new TextField(23);
public WS7()
{
add(T1,"Center");
Panel P = new Panel();
P.add(new Label ("发送的信息"));
P.add(T2);
T2.addActionListener(this);
add(P,"South");
setSize(350,200);
setVisible(true);
setTitle("WS7");
addWindowListener (new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
(new Thread (this)).start();
}
public void actionPerformed(ActionEvent e1){
try {
String str = T2.getText();
byte[] buf = str.getBytes();
DatagramSocket D = new DatagramSocket();
InetAddress A = InetAddress.getLocalHost();
DatagramPacket P1 = new DatagramPacket (buf,buf.length,A,8001);
D.send(P1);
T2.setText("");
}
catch(Exception e2){
}
}
public void run()
{
try {
DatagramSocket D = new DatagramSocket(8002);
while(true)
{
D.receive(Pac);
String str = new String(Pac.getData(),0,Pac.getLength());
T1.append(Pac.getAddress()+" WS7说 "+str+"\n");
}
}
catch(Exception e3){
}
}
public static void main(String args[]){
new WS7();
}
}
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