客户端和服务器的Java套接字问题

Question

我在比较从客户端发送到服务器的字符串时遇到问题。我试图从客户端读取消息“HELLO”，然后从服务器回复hello。我的问题是，当我在服务器类中得到我的if语句时，我总是碰到else。我相信我无法理解哪些行正在收集数据或只是打印。同时要做一些研究，我想学习这个好东西。任何想法为什么，提前谢谢你？

服务器类：

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

public class Server { 

    public static void main(String[] args) throws Exception 
    { 
     Server myServer = new Server(); 
     myServer.run(); 
    } 

    public void run() throws Exception 
    { 

     //Initializes the port the serverSocket will be on 
     ServerSocket serverSocket = new ServerSocket(4200); 
      System.out.println("The Server is waiting for a client on port 4200"); 
     //Accepts the connection for the client socket 
     Socket socket = serverSocket.accept(); 

     InputStreamReader ir = new InputStreamReader(socket.getInputStream()); 
     BufferedReader br = new BufferedReader(ir); 
     String message = br.readLine(); 
     //Confirms that the message was received 
     System.out.println(message); 

      if(message == "HELLO") 
      { 
       PrintStream ps = new PrintStream(socket.getOutputStream()); 
       ps.println("Received our hello message."); 
      } 
      else 
      { 
       PrintStream ps = new PrintStream(socket.getOutputStream()); 
       ps.println("Did not receive your hello message"); 
      } 
    } 

} 

Client类：

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

public class Client { 

    public static void main(String[] args) throws Exception 
    { 
     Client myClient = new Client(); 
     myClient.run(); 
    } 

    public void run() throws Exception 
    { 
     Socket clientSocket = new Socket("cmps329.csit.selu.edu", 4200); 
     //Sends message to the server 
     PrintStream ps = new PrintStream(clientSocket.getOutputStream()); 
     ps.println("HELLO"); 
     //Reads and displays response from server 
     InputStreamReader ir = new InputStreamReader(clientSocket.getInputStream()); 
     BufferedReader br = new BufferedReader(ir); 
     String message = br.readLine(); 
     System.out.println(message);   
    } 

} 

Answer 1

使用

if (message.equals("HELLO")) 

对于为什么见How do I compare strings in Java?。