java - 为什么ServerSocket对象的accept方法返回具有不同端口的Socket对象

Question

我已经在 stackoverflow 上搜索了我的问题的答案，但我无法从这些线程中得​​到答案。我的问题是为什么 ServeerSocket 对象的 accept() 方法返回一个监听服务器计算机上不同端口的 Socket 对象，而服务器正在监听的端口是另一个端口。

JAVA代码:

package chat.server;

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

public class ServerApp {
    public String[] advices = {"Take smaller bites",
            "Go for the tight jeans. No they do NOT make you look fat.",
            "One word: inappropriate",
            "Just for today, be honest. Tell your boss what you *really* think",
            "You might want to rethink that haircut."};
    public ServerSocket serverSocket;

    public ServerApp()
    {
        try
        {
            serverSocket = new ServerSocket(4245);
            System.out.println("Server Started.");
        }catch (Exception exception)
        {
            exception.printStackTrace();
        }
    }

    public static void main(String[] args) {
        ServerApp server = new ServerApp();
        while(true)
        {
                server.sendMessage();
        }

    }

    public void sendMessage()
    {
        String advice;
        try
        {
            Socket socket = serverSocket.accept();//here comes my question
            System.out.println(socket.getPort());
            PrintWriter printWriter = new PrintWriter(socket.getOutputStream());

            advice = getAdvice();
            printWriter.write(advice);

            printWriter.close();
            System.out.println(advice);
        }catch (Exception exception)
        {
            exception.printStackTrace();
        }
    }

    private String getAdvice() {
        int random = (int) (Math.random() * advices.length);
        return advices[random];
    }
}

服务器从同一个端口号监听并应答客户端，这不是很正常吗？

Answer 1

如果您希望从连接的套接字获取值 4245(您的服务器套接字正在监听的端口)，您需要使用 getLocalPort，而不是 getPort。

getPort :

Returns the remote port number to which this socket is connected.

getLocalPort :

Returns the local port number to which this socket is bound.

(我的重点)