UDP和TCP示例程序

查看自己的IP地址

以管理员身份运行cmd

输入

ipconfig

复制图中的IPv4地址

UDP通信程序

UdpReceiver.java

import java.net.*;public class UdpReceiver {public static void main(String[] args) {// 监听端口（需与发送端保持一致）int listenPort = 8888;// 接收数据的缓冲区大小（这里设置为1024字节）byte[] receiveBuffer = new byte[1024];try (DatagramSocket socket = new DatagramSocket(listenPort)) {System.out.println("接收端已启动，正在监听端口 " + listenPort + " ...");// 创建用于接收数据的空数据报包DatagramPacket packet = new DatagramPacket(receiveBuffer, receiveBuffer.length);// 阻塞等待接收数据（程序会在此处暂停，直到收到数据）socket.receive(packet);// 解析接收到的数据String receivedMessage = new String(packet.getData(), 0, packet.getLength()  // 只取有效数据部分（避免缓冲区残留数据干扰）);// 打印发送方信息和接收内容System.out.println("收到来自 " + packet.getAddress().getHostAddress() + ":" + packet.getPort() + " 的消息：" + receivedMessage);} catch (SocketException e) {System.err.println("Socket创建失败（可能端口被占用）：" + e.getMessage());} catch (Exception e) {System.err.println("接收过程中发生异常：" + e.getMessage());}}
}

UdpSender.java

import java.net.*;public class UdpSender {public static void main(String[] args) {// 目标IP地址String targetIp = "172.18.92.212";// 目标端口（需与接收端保持一致）int targetPort = 8888;// 要发送的数据String message = "这是来自UDP发送端的测试消息！";try (DatagramSocket socket = new DatagramSocket()) {// 将字符串转换为字节数组byte[] sendData = message.getBytes();// 创建数据报包：指定目标地址、端口和要发送的数据DatagramPacket packet = new DatagramPacket(sendData, sendData.length, InetAddress.getByName(targetIp), targetPort);// 发送数据报socket.send(packet);System.out.println("发送成功！发送内容：" + message);} catch (SocketException e) {System.err.println("Socket创建失败：" + e.getMessage());} catch (UnknownHostException e) {System.err.println("目标IP地址解析失败：" + e.getMessage());} catch (Exception e) {System.err.println("发送过程中发生异常：" + e.getMessage());}}
}

运行

先启动接收端，再启动发送端

TCP通信程序

TcpClient.java

import java.io.*;
import java.net.*;public class TcpClient {public static void main(String[] args) {// 目标服务器IPString serverIp = "172.18.92.212";// 目标服务器端口（需与服务器端保持一致）int serverPort = 9999;// 要发送的数据String message = "这是来自TCP客户端的测试消息！";try (Socket socket = new Socket(serverIp, serverPort);OutputStream os = socket.getOutputStream();PrintWriter pw = new PrintWriter(os, true)) {  // 自动刷新缓冲区// 发送数据pw.println(message);System.out.println("客户端已连接服务器，消息发送成功：" + message);} catch (UnknownHostException e) {System.err.println("目标服务器IP解析失败：" + e.getMessage());} catch (ConnectException e) {System.err.println("连接失败（可能服务器未启动/端口错误）：" + e.getMessage());} catch (IOException e) {System.err.println("通信过程中发生异常：" + e.getMessage());}}
}

TcpServer.java

import java.io.*;
import java.net.*;public class TcpServer {public static void main(String[] args) {// 监听端口（需与客户端保持一致）int listenPort = 9999;try (ServerSocket serverSocket = new ServerSocket(listenPort)) {System.out.println("服务器已启动，正在监听端口 " + listenPort + " ...");// 阻塞等待客户端连接（程序会在此处暂停，直到有客户端连接）try (Socket clientSocket = serverSocket.accept()) {  // 接收到连接后自动关闭clientSocketInetSocketAddress clientAddress = (InetSocketAddress) clientSocket.getRemoteSocketAddress();System.out.println("客户端连接成功！客户端地址：" + clientAddress.getAddress().getHostAddress() + ":" + clientAddress.getPort());// 获取输入流读取客户端数据InputStream is = clientSocket.getInputStream();BufferedReader br = new BufferedReader(new InputStreamReader(is));// 读取一行数据（与客户端的println对应）String receivedMessage = br.readLine();System.out.println("收到客户端消息：" + receivedMessage);} catch (IOException e) {System.err.println("客户端连接处理异常：" + e.getMessage());}} catch (IOException e) {System.err.println("服务器启动失败（可能端口被占用）：" + e.getMessage());}}
}