java 批量代理端口例子，支持TCP和UDP

以下是一个Java批量代理端口的例子，支持TCP和UDP：

import java.io.IOException;
import java.net.*;

public class PortProxy {
    private static final int BUFFER_SIZE = 1024;
    private static final int TIMEOUT = 3000;

    private int srcPort;
    private String dstHost;
    private int dstPort;
    private boolean isTCP;

    public PortProxy(int srcPort, String dstHost, int dstPort, boolean isTCP) {
        this.srcPort = srcPort;
        this.dstHost = dstHost;
        this.dstPort = dstPort;
        this.isTCP = isTCP;
    }

    public void start() throws IOException {
        ServerSocket serverSocket = new ServerSocket(srcPort);
        while (true) {
            Socket socket = serverSocket.accept();
            new Thread(() -> {
                try {
                    if (isTCP) {
                        handleTCP(socket);
                    } else {
                        handleUDP(socket);
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }

    private void handleTCP(Socket socket) throws IOException {
        Socket dstSocket = new Socket();
        dstSocket.connect(new InetSocketAddress(dstHost, dstPort), TIMEOUT);

        byte[] buffer = new byte[BUFFER_SIZE];
        int len;
        while ((len = socket.getInputStream().read(buffer)) != -1) {
            dstSocket.getOutputStream().write(buffer, 0, len);
            dstSocket.getOutputStream().flush();

            len = dstSocket.getInputStream().read(buffer);
            socket.getOutputStream().write(buffer, 0, len);
            socket.getOutputStream().flush();
        }

        dstSocket.close();
        socket.close();
    }

    private void handleUDP(Socket socket) throws IOException {
        DatagramSocket dstSocket = new DatagramSocket();

        byte[] buffer = new byte[BUFFER_SIZE];
        int len;
        while ((len = socket.getInputStream().read(buffer)) != -1) {
            DatagramPacket packet = new DatagramPacket(buffer, len, InetAddress.getByName(dstHost), dstPort);
            dstSocket.send(packet);

            packet = new DatagramPacket(buffer, BUFFER_SIZE);
            dstSocket.receive(packet);
            socket.getOutputStream().write(packet.getData(), 0, packet.getLength());
            socket.getOutputStream().flush();
        }

        dstSocket.close();
        socket.close();
    }

    public static void main(String[] args) throws IOException {
        PortProxy tcpProxy = new PortProxy(8080, "localhost", 80, true);
        tcpProxy.start();

        PortProxy udpProxy = new PortProxy(8081, "localhost", 53, false);
        udpProxy.start();
    }
}

该例子创建了一个`PortProxy`类，用于代理指定端口的TCP或UDP流量。在`main`方法中，我们创建了两个实例分别代理本地8080端口的HTTP流量和本地8081端口的DNS流量。

在`start`方法中，我们使用一个循环不断接受客户端连接，并在新的线程中处理。处理过程中，我们首先连接到目标主机，并将数据从源端口传输到目标端口。对于TCP流量，我们使用`Socket`进行传输；对于UDP流量，我们使用`DatagramSocket`进行传输。

注意，UDP流量需要在传输数据之前先创建一个`DatagramSocket`，并将目标主机和端口封装在`DatagramPacket`中。在传输完数据后，我们需要关闭`DatagramSocket`，否则会一直等待数据到来，导致程序无法退出。