计算机网络聊天程序（分别采用UDP和TCP实现）java代码

在Java中，我们可以使用Socket API来创建基于UDP（用户数据报协议）和TCP（传输控制协议）的网络聊天程序。这里提供一个简化的示例，展示了如何基本地使用这两种协议：

**UDP实现（无连接，不可靠）**:

import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class UDPChatServer {
    private DatagramSocket serverSocket;

    public void start(int port) throws Exception {
        serverSocket = new DatagramSocket(port);
        byte[] buffer = new byte[1024];
        while (true) {
            DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
            serverSocket.receive(packet);
            String message = new String(packet.getData());
            System.out.println("Received message from client: " + message);
        }
    }

    // 这里省略了客户端发送消息的部分，因为UDP是无连接的
}

// UDP客户端类似
public class UDPChatClient {
    private DatagramSocket clientSocket;
    // 发送消息等操作...
}

**TCP实现（面向连接，可靠）**:

import java.io.*;
import java.net.Socket;

public class TCPChatServer {
    private ServerSocket serverSocket;

    public void start(int port) throws IOException {
        serverSocket = new ServerSocket(port);
        Socket clientSocket = null;
        try {
            clientSocket = serverSocket.accept();
            BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
            String inputLine;
            while ((inputLine = in.readLine()) != null) {
                System.out.println("Received message from client: " + inputLine);
                out.println("Message received");
            }
        } finally {
            if (clientSocket != null) {
                clientSocket.close();
            }
        }
    }
}

// TCP客户端类似
public class TCPChatClient {
    private Socket socket;
    // 发送接收消息、连接服务器等操作...
}

请注意，这只是一个基础示例，实际应用中需要处理异常、线程安全、错误检测等问题，并可能包含更复杂的交互机制。