当套接字在Java中读取输入时，while循环失败 [英] While loop fails when socket reading input in java

问题描述

所以我在从客户端读取输入时遇到问题.每当我在服务器类中使用if语句而没有while语句时，它都可以正常工作.有人可以指出为什么这可能会失败吗?

so I am having an issue with reading input from a client. It works completely fine whenever I am using my if statements without the while statements wrapped around it in the server class. Could anybody point me to why this may be failing?

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(9999);
        System.out.println("The Server is waiting for a client on port 9999");
        //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);

    //When this while is here.  The match fails and it goes to the else statement.
    //Without the while statement it will work and print "Received our hello message." 
    //when the client says HELLO.

     while(message != null)
     {
            if(message.equals("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");
            }
        }
    }
}

客户端类:

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

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("localhost", 9999);
        //Sends message to the server
        PrintStream ps = new PrintStream(clientSocket.getOutputStream());
        Scanner scan = new Scanner(System.in);
        String cMessage = scan.nextLine();
        ps.println(cMessage);
        //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);        
    }

}

推荐答案

您只在服务器端循环，而您忘了在客户端循环，我为您做了快速修复，还帮助您关闭了连接

You only loops at the Server side, while u forgot to loop at the Client side, I did a quick fix for you, and also help you closed your connections.

Server.java

Server.java

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(9999);
        System.out.println("The Server is waiting for a client on port 9999");
        //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

    //When this while is here.  The match fails and it goes to the else statement.
    //Without the while statement it will work and print "Received our hello message." 
    //when the client says HELLO.
        PrintStream ps = new PrintStream(socket.getOutputStream());
        while((message =br.readLine())!=null)
         {
             System.out.println(message);
                if(message.equals("HELLO"))
                {

                    ps.println("Received our hello message.");
                }
                if(message.equals("END"))
                {
                    ps.println("Client ended the connection");
                    break;
                }
                else
                {

                    ps.println("Did not receive your hello message");
                }
        }
        ps.close();
        br.close();
        ir.close();
        serverSocket.close();
    }
}

Client.java

Client.java

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

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("localhost", 9999);
        //Sends message to the server
        PrintStream ps = new PrintStream(clientSocket.getOutputStream());
        Scanner scan = new Scanner(System.in);
        String cMessage ="";
        InputStreamReader ir = new InputStreamReader(clientSocket.getInputStream());
        BufferedReader br = new BufferedReader(ir);
        while(!(cMessage.trim().equals("END"))){
        cMessage = scan.nextLine();
        ps.println(cMessage);
        //Reads and displays response from server
        String message = br.readLine().trim();
        System.out.println(message);
        }
        br.close();
        ir.close();
        scan.close();
        ps.close();
        clientSocket.close();
    }

}

这篇关于当套接字在Java中读取输入时，while循环失败的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！