如何使用服务器套接字在Java中一次监听一个客户端？

Question

import java.io.*;
import java.net.*;
class MultiServer
{
    public static void main(String[] args) throws IOException
    {
        ServerSocket serverSock=new ServerSocket(3000);
        //server socket creation

        System.out.println("waiting for client.........");

        Socket socket=serverSock.accept();

        System.out.println("client connected ");

        BufferedReader keyRead=new BufferedReader(new 

        inputStreamReader(System.in));
        OutputStream ostream=socket.getOutputStream();//sending to client
        PrintWriter pw=new PrintWriter(ostream,true);
        InputStream istream=socket.getInputStream();//receiving from      
        server(istream objehect)
        BufferedReader receiveRead=new BufferedReader(new 
        InputStreamReader(istream));
        String receiveMessage,sendMessage;
        while(true)
        {
            if((receiveMessage=receiveRead.readLine())!= null)
            {
                System.out.println("client:>"+ receiveMessage);
            }

            sendMessage=keyRead.readLine();
            pw.println(sendMessage);
            System.out.flush();//flush the Stream
            if(sendMessage.equals("bye"))
            {
                break;
            }  
        }
    }
}

this code is to connect a client at a time , but i want to display a message that the server is busy if other client attempts to chat with the same server. that message should respond on both the side.

Answer 1

i want to display a message that the server is busy if other client attempts to chat with the same server. that message should respond on both the side

Basically impossible. The listen() backlog queue will cause a subsequent client's connection attempt to complete and be queued for the next accept() call by the server. There is nothing you can do about this short of closing the listening socket until you're ready to accept the next client, which introduces all kinds of timing constraints.

You could set a flag while you have a client and check it when you accept another one, and send him the message and disconnect him, but I fail to see the point.

that message should respond on both sides

What both sides? The side of the new client and who else?

Strange requirement. How can a chat server only want one client? Who is he chatting to?