java 代理端口转发，并计算流量

以下是一个简单的Java代理程序，它将所有传入的流量转发到指定的目标主机和端口，并计算传输的字节数。

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

public class ProxyServer {
    public static void main(String[] args) throws IOException {
        int localPort = 8888;
        String remoteHost = "example.com";
        int remotePort = 80;

        ServerSocket serverSocket = new ServerSocket(localPort);
        System.out.println("Proxy server listening on port " + localPort);

        while (true) {
            Socket clientSocket = serverSocket.accept();
            System.out.println("Client connected from " + clientSocket.getRemoteSocketAddress());

            Socket serverSocket1 = new Socket(remoteHost, remotePort);
            System.out.println("Connected to remote server " + remoteHost + ":" + remotePort);

            new Thread(() -> {
                try {
                    InputStream clientIn = clientSocket.getInputStream();
                    OutputStream clientOut = clientSocket.getOutputStream();
                    InputStream serverIn = serverSocket1.getInputStream();
                    OutputStream serverOut = serverSocket1.getOutputStream();

                    byte[] buffer = new byte[1024];
                    int bytesRead;

                    long totalBytes = 0;
                    while ((bytesRead = clientIn.read(buffer)) != -1) {
                        serverOut.write(buffer, 0, bytesRead);
                        totalBytes += bytesRead;
                    }

                    clientSocket.shutdownInput();
                    serverSocket1.shutdownOutput();

                    while ((bytesRead = serverIn.read(buffer)) != -1) {
                        clientOut.write(buffer, 0, bytesRead);
                        totalBytes += bytesRead;
                    }

                    clientSocket.shutdownOutput();
                    serverSocket1.shutdownInput();

                    clientSocket.close();
                    serverSocket1.close();

                    System.out.println("Transferred " + totalBytes + " bytes");
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }
}

在上面的代码中，我们首先创建一个ServerSocket来侦听传入的连接。一旦有一个客户端连接，我们就创建一个到目标主机和端口的Socket。然后，我们使用两个线程来读取和写入每个连接的数据。在每个线程中，我们使用一个字节数组缓冲区来读取和写入数据，并计算传输的字节数。最后，我们关闭所有连接并打印传输的字节数。

请注意，上面的代码只是一个简单的代理，它没有进行任何身份验证或安全性检查。在实际应用中，您应该根据需要添加这些功能。