如何在服務器/聊天客戶端程序中向除發件人以外的所有聊天用戶發送消息

Question

我有一個聊天程序，可以向所有聊天用戶（包括發件人）發送消息。 它需要發送給除發件人以外的所有人。 此外，似乎已將每個聊天用戶的已發送消息發送到服務器一次。 例如，如果有三個聊天用戶，如果說“你好”，它將向服務器發送“你好”三次。 這是我的代碼，問題出在run方法上：

import java.io.*;
import java.net.*;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Set;

public class BroadcastChatServer {


private static Hashtable<String, PrintWriter> writers = new Hashtable<>();  //Hash table for Client Names and corresponding PrintWriter objects
private static Hashtable<Integer, String> clientNames = new Hashtable<>();  //Hash table for Client IDs and corresponding message received
private static ServerSocket ServerSock;
private static int PORT=1234;


public static void main(String[] args) throws IOException { //main method
    try{
        ServerSock=new ServerSocket(3456);
    }
    catch(IOException e){
        System.out.println("can't listen on PORT");
        System.exit(1);
    }

    do{
        Socket client=null;
        System.out.println("Listening for connection...");
        try{
            client=ServerSock.accept();
            System.out.println("New client accepted");
            ClientHandler handler=new ClientHandler(client);
            handler.start();
        }
        catch(IOException e){
            System.out.println("accept failed");
            System.exit(1);
        }
        System.out.println("Connection successful");
        System.out.println("Listening for input..");
    }while(true);       
}//ends main




private static class ClientHandler extends Thread {//Make the ClientHandler a class inside the main class as below
private Socket client;
private BufferedReader in;
private PrintWriter out;

public ClientHandler(Socket socket) {

    client=socket;
    try{
        in=new BufferedReader(new InputStreamReader(client.getInputStream()));
        out=new PrintWriter(client.getOutputStream(),true);
    }
    catch(IOException e){
        e.printStackTrace();
    }

}

public void run() {
    try {
        String received;
        int message = 1;
        do {
            int index = 0;
            received = in.readLine();
            if (message == 1) {
                String clientName = getName().substring(getName().length() - 1);
                int clientNum = Integer.parseInt(clientName);
                //add client ID and message received to the clientnames hash table
                clientNames.put(clientNum, received);
                System.out.println(clientNames.get(clientNum) + " has joined");
                //add client name and corresponding PrintWriter to the writers hash table
                writers.put(clientNames.get(clientNum),out);
                //loop through the writers hash table and broadcast to all clients
                //that a new client has joined
                for (PrintWriter writer : writers.values()) {
                    writer.println( clientNames.get(clientNum) + " has joined");
                }
                message++;
            } else {
                String clientName = getName().substring(getName().length() - 1);
                int clientNum = Integer.parseInt(clientName);
                //Loop through the writers keySet, that is, (for String client:writers.keySet())
                for (String client:writers.keySet()){

                    //broadcast to all clients except this one                      
                    System.out.println("Message from " + clientNames.get(clientNum) + ": " + received);

                }


            }
        } while (!received.equals("BYE"));
    } 
    catch (IOException e) {
        System.out.println("failed");
        System.exit(1);
    }
}//ends run
}

}//ends broadcast chat server

Answer 1

看一下觀察者設計模式。 在那種情況下很好，並且很容易實現。