Java - 客户端和服务器通信问题

Question

我正在尝试创建一个简单的 Java 聊天应用程序，但遇到了一些问题。

下面是我的两个类的代码：

Serveur.java：

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

class Serveur{

    private String msgClient, msgServeur;
    private ServerSocket serverSocket;
    private DataOutputStream out;
    private Socket socket;
    private int port;
    private BufferedReader in;

    public Serveur() throws IOException{
        System.out.println("Serveur OK...");
        this.port = 21;
        this.serverSocket = new ServerSocket(this.port);
        while(true){
            this.socket = serverSocket.accept();
            this.in = new BufferedReader(new InputStreamReader(this.socket.getInputStream()));
            this.out = new DataOutputStream(this.socket.getOutputStream());
            this.msgClient = this.in.readLine();
            System.out.println("Received: " + this.msgClient);
            this.msgServeur = this.msgClient.toUpperCase() + '\n';
            send(this.msgServeur);
        }
    }

    public void send(String msg) throws IOException{
        this.out.writeBytes(msg);
    }

    public static void main(String argv[]) throws Exception {
        Serveur serveur = new Serveur();
    }
}

Client.java：

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

class Client{

    private String sentence;
    private String modifiedSentence;
    private int port;
    private BufferedReader inUser;
    private BufferedReader inServeur;
    private Socket socket;
    private DataOutputStream out;

    public Client() throws UnknownHostException, IOException{
        this.sentence = "";
        this.modifiedSentence = "";
        this.port = 21;
        this.inUser = new BufferedReader(new InputStreamReader(System.in));
        this.socket = new Socket("localhost", this.port);
        this.out = new DataOutputStream(this.socket.getOutputStream());
        this.inServeur = new BufferedReader(new InputStreamReader(this.socket.getInputStream()));
        sentence = this.inUser.readLine();
        this.out.writeBytes(sentence + '\n');
        modifiedSentence = this.inServeur.readLine();
        System.out.println("FROM SERVER: " + modifiedSentence);
        this.socket.close();
    }

    public static void main(String argv[]) throws Exception{
        Client client = new Client();
    }
}

我有两个问题：
- 客户端发送消息，服务器返回相同的大写消息。如何允许客户端在不立即关闭其套接字连接的情况下发送消息？
- 服务器看起来不错，但是当我有多个客户端时，连接多个客户端会有什么变化吗？如何向特定客户端广播消息和消息？

Answer 1

客户端发送消息，服务器返回相同的消息 大写。我怎样才能让客户端发送无限的消息和 发送第一条消息后不要自行销毁？

让客户端使用循环

boolean quit = false;
while (!quit) {
    sentence = this.inUser.readLine();
    quit = sentence.trim().equals("quit");
    this.out.writeBytes(sentence + '\n');
    modifiedSentence = this.inServeur.readLine();
    System.out.println("FROM SERVER: " + modifiedSentence);
}
this.socket.close();

服务器看起来不错，但是当我有多个客户端时，会吗 在多个客户端之间有所不同？我该如何广播？发送 给重点客户的消息？

是的，此服务器阻止读取第一个客户端，因此任何其他客户端都必须等待。您可能希望将每个客户端上的阻塞代码放在单独的线程中，或者将其提交给ExecutiveService。并且特定于客户端的所有变量都不能在单个服务器类中，因为您需要为每个客户端设置一组。

while (true) {
    final Socket socket = serverSocket.accept();
    new Thread(() -> {
        try {
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            DataOutputStream out = new DataOutputStream(socket.getOutputStream());
            boolean quit = false;
            while (!quit) {
                String msgClient = in.readLine();
                quit = msgClient.trim().equals("quit");
                System.out.println("Received: " + msgClient);
                String msgServeur = msgClient.toUpperCase() + '\n';
                out.writeBytes(msgServeur);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }).start();
}