java - 在 Java 中使用外部 IP 地址建立连接

Question

我正在尝试构建一个聊天程序。我编写了代码，一切正常，并且在我使用我的计算机并使用 127.0.0.1 连接时仍然运行良好。我也成功地在我的笔记本电脑和我的电脑之间成功连接，它们运行在同一个路由器上。 (我使用内部 IP 地址 10.0.0.3 来执行此操作)。

现在我正在尝试在我的路由器和其他路由器之间建立连接。为此，我正在尝试连接到外部 IP 地址。我通过我的路由器做端口转发部分，我也做了一个静态 IP。当我运行代码时，我总是收到“连接被拒绝错误”。

代码如下:

主服务器.java:

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

public class MainServer {
  private ArrayList<Socket> sockets;
  public MainServer() {
    ServerSocket server_socket;
    try {
      server_socket = new ServerSocket(5005);
      sockets = new ArrayList<Socket>();
      System.out.println("server is now running");
      while(true) {
        Socket socket = server_socket.accept();
        sockets.add(socket);
        try {
          PrintWriter writer = new PrintWriter(socket.getOutputStream());
          writer.println("---you are connected to the server---\r\n");
          writer.flush();
        } catch(Exception e) {e.printStackTrace();}
        System.out.println("server connected to " + socket.getInetAddress());
        Reader reader = new Reader(socket);
        Thread thread = new Thread(reader);
        thread.start();
      }
    } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
  }

  public static void main(String[] args) {
    MainServer server = new MainServer();
  }
  class Reader implements Runnable {
    Socket socket;
    public Reader(Socket socket) {
      this.socket=socket;
    }
    public void run() {
      while(true) {
        try {
          InputStreamReader stream_reader = new InputStreamReader(socket.getInputStream());
          BufferedReader reader = new BufferedReader(stream_reader);
          while(true) {
            String str = reader.readLine();
            if(str==null)
              continue;
            System.out.println("message from the client " + socket.getInetAddress() + ": " + str);
            send_back_message(str);
          }
        } catch (IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        }
      }
    }
    public void send_back_message(String str) {
      try {
        for(Socket send_to_socket: sockets) {
          PrintWriter writer = new PrintWriter(send_to_socket.getOutputStream());
          writer.println(send_to_socket.getInetAddress()+ ": " + str);
          writer.flush();
        }
      } catch(Exception e) {e.printStackTrace();}
    }
  }
}

客户端.java:

public Client() {
  frame = new JFrame();
  JPanel panel = new JPanel();
  chat = new JTextArea(20,40);
  chat.setEditable(false);
  JScrollPane scroll = new JScrollPane(chat);
  text = new JTextField(32);
  JButton send = new JButton("Send");
  send.addActionListener(new SendButtonListener());
  panel.add(scroll);
  panel.add(text);
  panel.add(send);
  frame.getContentPane().add(panel);
  frame.setSize(500,500);
  frame.setVisible(true);
  try {
    socket = new Socket("77.126.189.65",5005);
  } catch (Exception e) {
    e.printStackTrace();
  }
  Thread thread = new Thread(new ClientReader());
  thread.start();
}
public static void main(String[] args) {
  Client client = new Client();
}
class SendButtonListener implements ActionListener {
  public void actionPerformed(ActionEvent e) {
    try {
      PrintWriter writer = new PrintWriter(socket.getOutputStream());
      writer.println(text.getText());
      writer.flush();
      text.setText("");
    } catch (IOException e1) {
      e1.printStackTrace();
    }
  }
}
class ClientReader implements Runnable {
  public void run() {
    try {
      InputStreamReader stream_reader = new InputStreamReader(socket.getInputStream());
      BufferedReader reader = new BufferedReader(stream_reader);
      while(true) {
        String str = reader.readLine();
        if(str==null)
          continue;
        chat.setText(chat.getText() + str + "\r\n" );
      }
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}
}

我也试过this tool .当我运行 MainServer 文件并试用该工具时，我得到了肯定的答案。我对自己的 Eclipse 也很满意。当我的 MainServer 成功连接时，它会使用以下几行打印有关它的消息:

Socket socket = server_socket.accept();
System.out.println("server connected to " + socket.getInetAddress());

所以每次我在上面的工具中单击“检查”按钮时，我都会在我的 Eclipse 控制台(system.out.println 部分)中收到一条消息:

server connected to /69.163.149.200

因此我认为问题可能是没有连接到 MainServer 或 portforwading/firewall/static IP。

我还认为可能会出现问题，因为我正在尝试从我自己的路由器设备连接到我自己的路由器。在接下来的半小时内，我将让 MainServer 文件保持打开状态，这样如果有人可以在他的计算机上运行 Client.java，那将会很有帮助。

Answer 1

您尝试做的事情有点奇怪，但这是可能的。

你只需要知道你的路由器是否支持NAT Loopback / NAT Reflection并激活它。

NAT-loopback

Also known as NAT-hairpinning or NAT-reflection. NAT-loopback is a feature in many consumer routers which allows a user to connect to its own public IP address from inside the LAN-network. This is especially useful when a website (with domain) is hosted at that IP address.