package org.dragon;
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;
/**
 * 用于雙向通信的客戶端
 * */
public class Client {
	private static final String REMOTE_HOST = "公網(wǎng)IP";
	private static final String LOCAL_HOST = "127.0.0.1";
	public static void main(String[] args) {
		try {
			Socket proxy = new Socket(REMOTE_HOST, 10000);       
			System.out.println("Connect Server Successfully!");
			ProxyConnection proxyConnection = new ProxyConnection(proxy);  // 維持和內(nèi)網(wǎng)穿透服務端的長連接
			// 可以實現(xiàn)同一個人多次訪問
			while (true) {
				Msg msg = proxyConnection.receiveMsg();
				Connection connection = new Connection(new Socket(LOCAL_HOST, 8080));
				connection.sendMsg(msg);    // 將請求報文發(fā)送給內(nèi)網(wǎng)服務器，即模擬發(fā)送請求報文
				msg = connection.receiveMsg();  // 接收內(nèi)網(wǎng)服務器的響應報文
				proxyConnection.sendMsg(msg);  // 將內(nèi)網(wǎng)服務器的響應報文轉(zhuǎn)發(fā)給公網(wǎng)服務器（內(nèi)網(wǎng)穿透服務端）
			}
		} catch (UnknownHostException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

package org.dragon;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
/**
 * 維持用戶和服務器的連接
 * */
public class Connection {
	private InputStream input;
	private OutputStream output;
	public Connection(Socket client) throws IOException {
		this.input = new BufferedInputStream(client.getInputStream());
		this.output = new BufferedOutputStream(client.getOutputStream());
	}
	public Msg receiveMsg() throws IOException {
		byte[] msg = new byte[2*1024];
		int len = input.read(msg);
		return new Msg(len, msg);
	}
	public void sendMsg(Msg msg) throws IOException {
		output.write(msg.getMsg(), 0, msg.getLen());
		output.flush();  // 每一次寫入都要刷新，防止阻塞。
	}
}

package org.dragon;
public class Msg {
	private int len;
	private byte[] msg;
	public Msg(int len, byte[] msg) {
		this.len = len;
		this.msg = msg;
	}
	public int getLen() {
		return len;
	}
	public byte[] getMsg() {
		return msg;
	}
	@Override
	public String toString() {
		return "msg: " + len + " --> " + new String(msg, 0, len);
	}
}

package org.dragon;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;
/**
 * @author Alfred
 * 
 * 代理服務器和代理客戶端是用于維持兩者之間通信的一個長連接Socket，
 * 主要的目的是因為雙方之間的通信方式是全雙工的，它們的作用是為了傳遞報文。
 * */
public class ProxyConnection {
	private Socket proxySocket;
	private DataInputStream input;
	private DataOutputStream output;
	public ProxyConnection(final Socket socket) throws UnknownHostException, IOException {
		proxySocket = socket;
		input = new DataInputStream(new BufferedInputStream(proxySocket.getInputStream()));
		output = new DataOutputStream(new BufferedOutputStream(proxySocket.getOutputStream()));
	}
	/**
	 * 接收報文
	 * @throws IOException 
	 * */
	public Msg receiveMsg() throws IOException {
		int len = input.readInt();
		if (len <= 0) {
			throw new IOException("異常接收數(shù)據(jù)，長度為：" + len);
		}
		byte[] msg = new byte[len];
		int size = input.read(msg);  // 這里到底會不會讀取到這么多，我也有點迷惑！
		return new Msg(size, msg);   // 為了防止出錯，還是使用一個記錄實際讀取值size
	}
	/**
	 * 轉(zhuǎn)發(fā)報文
	 * @throws IOException 
	 * */
	public void sendMsg(Msg msg) throws IOException {
		output.writeInt(msg.getLen());
		output.write(msg.getMsg(), 0, msg.getLen());
		output.flush();  // 每一次寫入都需要手動刷新，防止阻塞。
	}
}

package org.dragon;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
/**
 * 用于雙向通信的服務器
 * */
public class Server {
	public static void main(String[] args) {
		try (ServerSocket server = new ServerSocket(10000)) {
			// 用于交換控制信息的Socket
			Socket proxy = server.accept();
			ProxyConnection proxySocket = new ProxyConnection(proxy);
			// 用于正常通訊的socket
			while (true) {
				Socket client = server.accept();
				Connection connection = new Connection(client);
				Msg msg = connection.receiveMsg();  // 接收用戶的請求報文
				proxySocket.sendMsg(msg);           // 轉(zhuǎn)發(fā)用戶的請求報文給內(nèi)網(wǎng)服務器
				msg = proxySocket.receiveMsg();     // 接收內(nèi)網(wǎng)服務器的響應報文
				connection.sendMsg(msg);            // 轉(zhuǎn)發(fā)內(nèi)網(wǎng)服務器的響應報文給用戶
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

package org.dragon.controller;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class Controller {
	@GetMapping("/loveEN")
	public String testEN() {
		return "I love you yesterday and today!";
	}
	@GetMapping("/loveZH") 
	public String loveZH() {
		return "有一美人兮，見之不忘。一日不見兮，思之如狂。鳳飛翱翔兮，四海求凰。無奈佳人兮，不在東墻。";
	}
	@GetMapping("/loveJson")
	public Map<String, String> loveJson() {
		HashMap<String, String> map = new LinkedHashMap<>();
		map.put("english", "I love you yesterday and today!");
		map.put("chinese", "有一美人兮，見之不忘。一日不見兮，思之如狂。"
				+ "鳳飛翱翔兮，四海求凰。無奈佳人兮，不在東墻。");
		return map;
	}
}