在JAVA中建立客户端服务器通信？

Question

I want to perform a two way communication between the client and the server and so far i have achieved one way communication. My code in JAVA looks like,

ServerSide

    public class server{
        @SuppressWarnings("deprecation")
        public static void main(String[] args)
        {
            try{
            ServerSocket s=new ServerSocket(9998);
            Socket ss=s.accept();
            DataInputStream din=new DataInputStream(ss.getInputStream());
            DataInputStream uip=new DataInputStream(System.in);
            DataOutputStream dout=new DataOutputStream(ss.getOutputStream());
            System.out.println("Enter message to send to client\n");
            String stc=uip.readLine();
            dout.writeBytes(""+stc);
            din.close();
            dout.close();
            uip.close();    
        }
            catch(Exception e)
            {
                System.out.println(e);
            }`enter code here`
    }
    }

ClientSide

   public class client{
    public static void main(String[] args)
    {
        try{
        Socket ss=new Socket("localhost",9998);
        DataInputStream din=new DataInputStream(ss.getInputStream());
        DataInputStream uip=new DataInputStream(System.in);
        DataOutputStream dout=new DataOutputStream(ss.getOutputStream());
        String msg=din.readLine();
        System.out.println("Received msg is "+msg);

        din.close();
        dout.close();
        uip.close();


    }
        catch(Exception e)
        {
            System.out.println(e);
        }
}
}

I tried to get input in the client side and tried to send in the same way to server. but thats not working. Where am i getting wrong? How Should i achieve a two way communication.

In the client side i got input from user and used .writeBytes(value); and performed readLine() in din in the server side as i have done above in one way communication. But that doesn't work. Where am i doing it wrong?

Answer 1

I'm assuming you are running both program in different process, and you are only expecting result on client which you are sending from server. From client you are not sending anything to server.

If you are not getting any error try to flush the stream like:

dout.writeBytes(""+stc);
dout.flush();

---

From comment: Added following code.

Receive code on Server side

// this is your code on server
dout.writeBytes(""+stc);
//Add this code 
String msgServer = din.readLine();
System.out.println("Received msg on Server: " + msgServer );

Add client side code:

// this is your code on client
System.out.println("Received msg is "+msg);
dout.writeBytes("Test data from client");
dout.flush();

Answer 2

The best approach to create a double communication system is to create two threads one for writing messages and one to receive messages (both on client and server side).

The listening thread receive a message wake itself and do something. If a response is needed it create the response and add it to a queue.

The writing thread periodically check the queue of messages to be sent. If there are it sends them.

Answer 3

This is the best way for bidirectional client server communication.. "dout.shutdownOutput();" code this line after send function in client side.This is the function named as half socket closed it will helps to back and forth communication.