Question

I am just working on my assignment of client-server and found an program online of a server.java as:

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

public class MyServer{

    public static void main(String [] args){
        try{
        ServerSocket ssc = new ServerSocket(7500);

        Socket newSsc = ssc.accept();
        DataInputStream din = new DataInputStream(newSsc.getInputStream());
        DataOutputStream dout = new DataOutputStream(newSsc.getOutputStream());

        PrintWriter pw = new PrintWriter(dout);
        pw.println("Hello! Welcome to vinit's server.");
        boolean more_data = true;
        while(more_data){
            String line = din.readLine();
            if(line == null){
                more_data = false;
            }
            else{
                pw.println("From Server "+line + "\n");
                System.out.println("From Client "+line);
                if(line.trim().equals("QUIT"))
                    more_data = false;
            }
        }
            newSsc.close();
        }
        catch(IOException e){
            System.out.println("IO error");

        }   

    }
}

THen after I used this server by typing the command as

$ telnet 127.0.0.1 7500

Now I want to ask how my server will be getting null from client, i mean what should be entered so that server will get null

Thanks in Advance.

Answer 1

You have to gracefully close the TCP connection, simply CTRL+C or killing the telnet program won’t do, it’ll result in an exception in the Java code.

This is a challenge with telnet, depending on your keyboard layout and OS.

$ telnet localhost 8080
Trying 127.0.0.1...
Connected to localhost (127.0.0.1).
Escape character is '^]'.
^]
telnet> quit
Connection closed.

Basically, once inside telnet you’ll have to press the telnet escape key, which on my keyboard is CTRL+å and type quit , and on an US keyboard probably is what the telnet program tells you, just CTRL+]

If you’re using the netcat program instead of telnet, you can just hit ctrl+d , or pipe some text to it, and the connection will be closed normally.

echo "Some text" | nc localhost 7500