Java 不是",；“本地主机”；套接字网络示例

您可能听说过使用java套接字网络。一个简单的总结是，他正在使用

127.0.0.1

IP地址在客户端和服务器之间创建连接。一切都对我有用，但当我试图更改代码并将其放在两台独立的计算机（客户端和服务器）上时，它无法建立连接。我做错了什么

服务器代码

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

public class Server extends JFrame{

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

//constructor
public Server()
{

    super("My Instant Messenger");
    userTextField = new JTextField();
    userTextField.setEditable(false);

    userTextField.addActionListener(new ActionListener(){
     public void actionPerformed(ActionEvent event)
     {

        sendMessage(event.getActionCommand());
        userTextField.setText("");

     }
    }
    );

    add(userTextField, 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 e){
       showMessage("\n Server ended the connection! ");  
      }finally{
       closeCrap();  
      }
  }

 }catch(IOException e){
  e.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 coversation
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 e){
            showMessage("\n idk wtf that user sent!");
        }
    }while(!message.equals("CLIENT - END"));
}

//close streams and sockets after you are done chating
private void closeCrap(){
    showMessage("\n Closing connection... \n");
    ableToType(false);
    try{

        output.close();
        input.close();
        connection.close();

    }catch(IOException e){
        e.printStackTrace();
    }
}

//send a message to client
private void sendMessage (String message){
    try{

        output.writeObject("SERVER -  " + message);
        output.flush();
        showMessage("\nSERVER - " + message);

    }catch(IOException e){
        chatWindow.append("\n ERROR: DUDE I CANT SEND THAT MESSAGE!");
    }
}    

//update 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(){
        userTextField.setEditable(tof);
    }
    }
    );
}

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

}

客户端代码

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

public class Client extends JFrame{
private JTextField userTextField;
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");
    serverIP = host;
    userTextField = new JTextField();
    userTextField.setEditable(false);
    userTextField.addActionListener(
        new ActionListener(){
            public void actionPerformed(ActionEvent event){
                sendMessage(event.getActionCommand());
                userTextField.setText("");
            }
        }
    );
    add(userTextField, 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 e){
        showMessage("\n Client terminated connection");
    }catch(IOException e){
        e.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 chating with server
private void whileChatting() throws IOException{
    ableToType(true);
    do{
        try{
            message = (String) input.readObject();
            showMessage("\n" + message);
        }catch(ClassNotFoundException e){
            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 e){
        e.printStackTrace();
    }
}

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

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

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

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

---

在IPv4和v6平台上运行时，问题在于Java本身

请尝试将serverSocket绑定到IPv4地址

“0.0.0.0”

，这意味着此主机上的所有IP都可用，或者使用客户端代码中的IP（

192.168.x.x

）

像这样

server = new ServerSocket(6789, 100, InetAddress.getByName("0.0.0.0"));

---

我想你算出了这两台计算机的两个IP地址。你们要开哪个港口？是否有防火墙处于活动状态？（你能给我们看一下你的代码吗？）？其他网络硬件？绑定到套接字时出错？@PhilW port是6789，我也尝试了新的ServerSocket（0），但它仍然无法连接。是否有异常？您可以将代码添加到问题中吗？您需要做的事情是，在尝试运行程序之前，首先确保您可以从客户端ping服务器，然后还要确保服务器绑定的端口未被防火墙阻止。如果我使用服务器的外部IP地址，会发生什么情况？我想这就是我在不同的计算机上工作所必须做的。我试过这样做，但不起作用，我假设外部IP是您的公共WAN IP（internet）。这取决于您的网络配置：如果您有路由器/调制解调器，WAN-IP将分配给该设备，并且您的电脑有LAN IP（10.x.x.x或192.168.x.x或类似的）。您需要使用NAT（网络地址（“端口转发”）转换）来实现这一点。我将对此进行研究，但NAT（端口转发）与java中的套接字网络在哪里发生冲突？因为每次我读到其他问题和答案时，人们似乎都不会一起提到它们。这与Java无关，而是与网络有关。您必须分层查看：告诉Java打开套接字会告诉OS（操作系统）打开网络驱动程序上的套接字等。当您连接时，它会通过OS、防火墙、路由器、调制解调器等。因此，在这些步骤的任何一点上，都可能存在一个问题，这不是Java的问题，而是网络的问题（或操作系统）。由于出站连接（PC到Internet）通常正常工作，因此只剩下防火墙和路由（NAT）配置来配置入站通信