JAVA 服务器套接字 - 帮助它不会发送

Question

我已经为此工作了将近一个星期，我已经将它精简为最基本的代码，但客户端仍然收不到来自客户端的消息。任何帮助将不胜感激。

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class Server {

    Socket socket;
    JTextArea textShow;
    PrintWriter writer;
    static String message;

    JButton buttonSend;

    // LAUNCH
    public static void main(String[] args) throws Exception {
        Server servobj = new Server();
        servobj.Server();

    }

    public void Server() throws Exception {

        // dECLARE
        JFrame frame = new JFrame();
        frame.setTitle("The Server");
        JPanel panel = new JPanel();
        textShow = new JTextArea(10, 40);
        JTextField textSend = new JTextField(35);
        buttonSend = new JButton("SEND");
        JScrollPane scrollPane = new JScrollPane(textShow,
                JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
                JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);

        // INITIALIZE
        frame.getContentPane().add(panel);
        panel.add(textShow);
        textShow.setLineWrap(true);
        panel.add(scrollPane);
        panel.add(textSend);
        panel.add(buttonSend);
        frame.setSize(500, 500);
        frame.setVisible(true);
        setupServer();

    }

    // SETTING UP THE SERVERS
    public void setupServer() throws Exception {

        ServerSocket servSock = new ServerSocket(443);

        socket = servSock.accept();
        System.out.println("Server Socket accepted");

        writer = new PrintWriter(socket.getOutputStream());
        writer.println("Hello");
        System.out.println("MESSAGE SENT");

        InputStreamReader isr = new InputStreamReader(socket.getInputStream());
        BufferedReader reader = new BufferedReader(isr);
        message = reader.readLine();
        System.out.println(message);

    }

}

import java.awt.TextField;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class Client {

    Socket socket;
    PrintWriter writer;
    static JTextArea textShow;
    TextField textSend;

    // LAUNCH
    public static void main(String[] args) throws Exception {
        Client clientobj = new Client();
        clientobj.Client();

    }

    public void Client() throws Exception {

        // dECLARE
        JFrame frame = new JFrame();
        frame.setTitle("Client");
        JPanel panel = new JPanel();
        textShow = new JTextArea(10, 40);
        JTextField textSend = new JTextField(35);
        JButton buttonSend = new JButton("SEND");
        JScrollPane scrollPane = new JScrollPane(textShow,
                JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
                JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);

        // INITIALIZE
        frame.getContentPane().add(panel);
        panel.add(textShow);
        textShow.setLineWrap(true);
        panel.add(scrollPane);
        panel.add(textSend);
        panel.add(buttonSend);
        frame.setSize(500, 500);
        frame.setVisible(true);

        setupConnections();
    }

    // SETTING UP THE CONNECTION
    public void setupConnections() throws Exception {

        Socket socket = new Socket("localhost", 443);
        System.out.println("Client accepted");

        // SETUP RECIEVE MESSAGE
        InputStreamReader isr = new InputStreamReader(socket.getInputStream());
        BufferedReader reader = new BufferedReader(isr);
        System.out.println("Done sam");
        String Message = reader.readLine();
        System.out.println(Message);
        System.out.println("Sent");

        // SETUP SEND MESSAGE
        writer = new PrintWriter(socket.getOutputStream());
        writer.println("Hello G");
        writer.flush();
        System.out.println("Network Established");

    }
}

Answer 1

看来你知道可能是什么问题，但你没有到处改正。

在你的客户中你有

// SETUP SEND MESSAGE
writer = new PrintWriter(socket.getOutputStream());
writer.println("Hello G");
writer.flush();

所以你意识到 PrintWriter 不会立即发送你的消息，但会把它放在内部缓冲区中，所以要强制发送给你调用 flush.

但是在服务器中您没有刷新该消息

writer = new PrintWriter(socket.getOutputStream());
writer.println("Hello");
System.out.println("MESSAGE SENT");

避免此类问题的最简单方法是使用 PrintWriter，它会自动刷新，就像您使用 println 时一样。这样的编写器可以通过 PrintWriter(OutputStream out, boolean autoFlush) 构造函数

创建

我们可以在哪里阅读

autoFlush - A boolean; if true, the println, printf, or format methods will flush the output buffer

因此请考虑在类

中使用此构造函数

writer = new PrintWriter(socket.getOutputStream(),true);

并且当您通过 println 发送消息时，它应该会自动刷新。

您当前的代码中还有一些其他可能的问题

您正在创建本地套接字变量而不是初始化套接字字段
你有与构造函数同名的方法，这不是好的做法，所以不要
```
public void Client(){

}

Client client = new Client();
client.Client();//<-here you are calling your method
```
您应该删除 return 类型 void 以创建该方法构造函数，这样您的代码将只减少到
```
Client client = new Client();
```

JAVA 服务器套接字 - 帮助它不会发送

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