Java实现端口映射/转发

  1 import java.io.IOException;
  2 import java.io.InputStream;
  3 import java.io.OutputStream;
  4 import java.net.ServerSocket;
  5 import java.net.Socket;
  6 import java.util.Date;
  7 import java.util.HashMap;
  8 
  9 public class SimpleForward {
 10     // 服务器
 11     private ServerSocket server;
 12     // 监听本地端口
 13     private int localPort = 1080;
 14     // 目标主机地址
 15     private String remoteHostAddr = "0.0.0.0";
 16     // 目标主机端口
 17     private int remoteHostPort = 8388;
 18     // 设置超时时间 30s
 19     private static int TIMEOUT = 30;
 20     // 客户端列表 用于删除失效连接和超时连接 这里的超时是指长时间没有流量的连接 不是连接超时
 21     private static HashMap<Socket, Date> clientList = new HashMap<>();
 22 
 23     public static void main(String[] args) throws IOException {
 24 //        new SimpleForward();
 25         new SimpleForward(1234, "127.0.0.1", 1080);
 26     }
 27 
 28     public SimpleForward() throws IOException {
 29         run();
 30     }
 31 
 32     public SimpleForward(int localPort, String remoteHostAddr, int remoteHostPort) throws IOException {
 33         this.localPort = localPort;
 34         this.remoteHostAddr = remoteHostAddr;
 35         this.remoteHostPort = remoteHostPort;
 36         run();
 37     }
 38 
 39     private void run() throws IOException {
 40         this.server = new ServerSocket(this.localPort);
 41         System.out.println("服务器开启成功");
 42         System.out.println("监听端口 : " + this.localPort);
 43         // 自动清除失效连接和超时连接
 44         new Thread(new AutoDestroy()).start();
 45         while (true) {
 46             Socket socket = server.accept();
 47             // 接收到请求就把socket扔进map,value为刷新时间
 48             clientList.put(socket, new Date());
 49             String address = socket.getRemoteSocketAddress().toString();
 50             System.out.println("新连接 ： " + address);
 51             // 建立与目标主机的连接
 52             Socket remoteHost = new Socket(this.remoteHostAddr, this.remoteHostPort);
 53             System.out.println("连接地址 : " + this.remoteHostAddr + ":" + this.remoteHostPort);
 54             // 端口转发
 55             new Thread(new Switch(socket, remoteHost.getInputStream(), socket.getOutputStream())).start();
 56             new Thread(new Switch(socket, socket.getInputStream(), remoteHost.getOutputStream())).start();
 57         }
 58     }
 59 
 60     // 用于端口转发
 61     private class Switch implements Runnable {
 62         private Socket socket;
 63         private InputStream in;
 64         private OutputStream out;
 65 
 66         Switch(Socket socket, InputStream in, OutputStream out) {
 67             this.socket = socket;
 68             this.in = in;
 69             this.out = out;
 70         }
 71 
 72         @Override
 73         public void run() {
 74             int length = 0;
 75             byte[] buffer = new byte[1024];
 76             try {
 77                 while (!socket.isClosed() && (length = in.read(buffer)) > -1) {
 78                     clientList.put(socket, new Date());
 79                     out.write(buffer, 0, length);
 80                 }
 81             } catch (IOException e) {
 82                 System.out.println("连接关闭");
 83             }
 84         }
 85     }
 86 
 87     // 用于清除失效连接和超时连接
 88     private class AutoDestroy implements Runnable {
 89 
 90         @Override
 91         public void run() {
 92             for (Socket socket : clientList.keySet()) {
 93                 Date lastTime = clientList.get(socket);
 94                 long time = new Date().getTime() - lastTime.getTime();
 95                 if (socket.isClosed() || time / 1000 >= TIMEOUT) {
 96                     try {
 97                         clientList.remove(socket);
 98                         socket.close();
 99                     } catch (IOException e) {
100                         e.printStackTrace();
101                     }
102                 }
103             }
104         }
105     }
106 }