Java 客户端如何通过外部IP地址连接到服务器？

下面的应用程序是一个由java开发的聊天程序，当我使用本地IP地址时，客户端可以完美地连接到服务器。但是，当我使用外部IP地址从两台不同的机器将客户机连接到服务器时，服务器只是一直等待连接，什么也没有发生。因此，我所需要的就是使用外部IP将客户机连接到服务器

客户机：java

import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Client extends JFrame{

   private JTextField userText;
   private JTextArea chatWindow;
   private ObjectOutputStream output;
   private ObjectInputStream input;
   private String message = "";
   private String serverIP;
   private Socket connection;

   //constructor
   public Client(String host){
      super("Client mofo!");
      serverIP = host;
      userText = new JTextField();
      userText.setEditable(false);
      userText.addActionListener(
         new ActionListener(){
            public void actionPerformed(ActionEvent event){
               sendMessage(event.getActionCommand());
               userText.setText("");
            }
         }
      );
      add(userText, BorderLayout.NORTH);
      chatWindow = new JTextArea();
      add(new JScrollPane(chatWindow), BorderLayout.CENTER);
      setSize(300,150);
      setVisible(true);
   }

   //connect to server
   public void startRunning(){
      try{
         connectToServer();
         setupStreams();
         whileChatting();
      }catch(EOFException eofException){
         showMessage("\n Client terminated connection");
      }catch(IOException ioException){
         ioException.printStackTrace();
      }finally{
         closeCrap();
      }
   }

   //connect to server
   private void connectToServer() throws IOException{
      showMessage("Attempting connection... \n");
      connection = new Socket(InetAddress.getByName(serverIP), 6789);
      showMessage("Connected to: " + connection.getInetAddress().getHostName() );
   }

   //set up streams to send and receive messages
   private void setupStreams() throws IOException{
      output = new ObjectOutputStream(connection.getOutputStream());
      output.flush();
      input = new ObjectInputStream(connection.getInputStream());
      showMessage("\n Dude your streams are now good to go! \n");
   }

   //while chatting with server
   private void whileChatting() throws IOException{
      ableToType(true);
      do{
         try{
            message = (String) input.readObject();
            showMessage("\n" + message);
         }catch(ClassNotFoundException classNotfoundException){
            showMessage("\n I dont know that object type");
         }
      }while(!message.equals("SERVER - END"));
   }

   //close the streams and sockets
   private void closeCrap(){
      showMessage("\n closing crap down...");
      ableToType(false);
      try{
         output.close();
         input.close();
         connection.close();
      }catch(IOException ioException){
         ioException.printStackTrace();
      }
   }

   //send messages to server
   private void sendMessage(String message){
      try{
         output.writeObject("CLIENT - " + message);
         output.flush();
         showMessage("\nCLIENT - " + message);
      }catch(IOException ioException){
         chatWindow.append("\n something messed up sending message hoss!");
      }
   }

   //change/update chatWindow
   private void showMessage(final String m){
      SwingUtilities.invokeLater(
         new Runnable(){
            public void run(){
               chatWindow.append(m);
            }
         }
      );
   }

   //gives user permission to type crap into the text box
   private void ableToType(final boolean tof){
      SwingUtilities.invokeLater(
         new Runnable(){
            public void run(){
               userText.setEditable(tof);
            }
         }
      );      
   }
}

客户：测试

import javax.swing.JFrame;

public class ClientTest {
   public static void main(String[] args) {
      Client charlie;
      charlie = new Client("127.0.0.1");
      charlie.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      charlie.startRunning();
   }
}

服务器：java

import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Server extends JFrame{

   private JTextField userText;
   private JTextArea chatWindow;
   private ObjectOutputStream output;
   private ObjectInputStream input;
   private ServerSocket server;
   private Socket connection;

   //constructor
   public Server(){
      super("Buckys Instant Messenger");
      userText = new JTextField();
      userText.setEditable(false);
      userText.addActionListener(
         new ActionListener(){
            public void actionPerformed(ActionEvent event){
               sendMessage(event.getActionCommand());
               userText.setText("");
            }
         }
      );
      add(userText, BorderLayout.NORTH);
      chatWindow = new JTextArea();
      add(new JScrollPane(chatWindow));
      setSize(300,150);
      setVisible(true);
   }

   //set up and run the server
   public void startRunning(){
      try{
         server = new ServerSocket(6789, 100);
         while(true){
            try{
               waitForConnection();
               setupStreams();
               whileChatting();
            }catch(EOFException eofException){
               showMessage("\n Server ended the connection! ");
            }finally{
               closeCrap();
            }
         }
      }catch(IOException ioException){
         ioException.printStackTrace();
      }
   }

   //wait for connection, then display connection information
   private void waitForConnection() throws IOException{
      showMessage(" Waiting for someone to connect... \n");
      connection = server.accept();
      showMessage(" Now connected to " + connection.getInetAddress().getHostName());
   }

   //get stream to send and receive data
   private void setupStreams() throws IOException{
      output = new ObjectOutputStream(connection.getOutputStream());
      output.flush();
      input = new ObjectInputStream(connection.getInputStream());
      showMessage("\n Streams are now setup! \n");
   }

   //during the chat conversation
   private void whileChatting() throws IOException{
      String message = " You are now connected! ";
      sendMessage(message);
      ableToType(true);
      do{
         try{
            message = (String) input.readObject();
            showMessage("\n" + message);
         }catch(ClassNotFoundException classNotFoundException){
            showMessage("\n idk wtf that user sent!");
         }
      }while(!message.equals("CLIENT - END"));
   }

   //close streams and sockets after you are done chatting
   private void closeCrap(){
      showMessage("\n Closing connections... \n");
      ableToType(false);
      try{
         output.close();
         input.close();
         connection.close();
      }catch(IOException ioException){
         ioException.printStackTrace();
      }
   }

   //send a message to client
   private void sendMessage(String message){
      try{
         output.writeObject("SERVER - " + message);
         output.flush();
         showMessage("\nSERVER - " + message);
      }catch(IOException ioException){
         chatWindow.append("\n ERROR: DUDE I CANT SEND THAT MESSAGE");
      }
   }

   //updates chatWindow
   private void showMessage(final String text){
      SwingUtilities.invokeLater(
         new Runnable(){
            public void run(){
               chatWindow.append(text);
            }
         }
      );
   }

   //let the user type stuff into their box
   private void ableToType(final boolean tof){
      SwingUtilities.invokeLater(
         new Runnable(){
            public void run(){
               userText.setEditable(tof);
            }
         }
      );
   }

}

服务器：测试

import javax.swing.JFrame;

public class ServerTest {
   public static void main(String[] args) {
      Server sally = new Server();
      sally.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      sally.startRunning();
   }
}

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您需要配置防火墙并设置端口转发

端口转发是其中重要的一个。基本上，您需要告诉路由器将所有传入的请求发送到指定的端口，在那里您的程序可以处理它们

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防火墙是另一个可能的问题，有时您的网络或计算机会阻止未知的请求。

好的，我必须在防火墙上打开同一个端口吗？您可以告诉我您必须如何允许服务器通过防火墙，并且您必须用服务器运行的端口转发路由器。如果需要，请随时询问更多说明。谢谢，这将有助于您配置防火墙和设置端口转发。