Question

I wrote this simple Java program which connects to internic server and returns the domain details. However, I am facing a strange problem. I may sound dumb but here is the program!

import java.io.*;
import java.net.*;
public class SocketTest {
    public static void main(String[] args) {
        String hostName;
        int i = 0;

        try {                  
            Socket socketClient = new Socket("whois.internic.net", 43);
            BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
            InputStream in = socketClient.getInputStream();
            OutputStream out = socketClient.getOutputStream();
            System.out.println("Please Enter the Host Name!!");
            hostName = bf.readLine();      
            hostName = hostName + "\n";
            byte[] buf = hostName.getBytes();
            out.write(buf);

            while((i = in.read()) != -1) {
                System.out.print((char)i);
            }

            socketClient.close();
        } catch(UnknownHostException uht) {
            System.out.println("Host Error");
        } catch(IOException ioe) {
            System.out.println("IO Error " + ioe);
        } catch(Exception e) {
            System.out.println("Exception " + e);
        }
    }
}

The program runs fine, without any runtime errors, but it shows no output when I try to print the result from internic server in the last piece of try block. I tried rearranging the code and found that if I place the bf.readLine() after creating socket streams, there is no output. However, if I place it before the socket creation (at the start of main method), the program displays intended output.

Is there any stream conflict or so? I am a newbie to networking in Java. The solution may be obvious but I am not able to understand! Please help me!!!

Answer 1

Move your input stream initialization after you send the domain to the output stream… This works for me locally:

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

public class SocketTest {
    public static void main(String[] args) {
        String hostName;
        int i = 0;
        try {
            Socket socketClient = new Socket("whois.internic.net", 43);
            BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));

            OutputStream out = socketClient.getOutputStream();
            System.out.println("Please Enter the Host Name!!");
            hostName = bf.readLine();
            hostName = hostName + "\n";
            byte[] buf = hostName.getBytes();
            out.write(buf);

            InputStream in = socketClient.getInputStream();
            while ((i = in.read()) != -1) {
                System.out.print((char) i);
            }
            in.close();
            out.close();
            socketClient.close();

        } catch (UnknownHostException uht) {
            System.out.println("Host Error");
        } catch (IOException ioe) {
            System.out.println("IO Error " + ioe);
        } catch (Exception e) {
            System.out.println("Exception " + e);
        }
    }
}

Output:

Please Enter the Host Name!!
yahoo.com

Whois Server Version 2.0

Domain names in the .com and .net domains can now be registered
with many different competing registrars. Go to http://www.internic.net
for detailed information.

YAHOO.COM.ZZZZZZZ.GET.ONE.MILLION.DOLLARS.AT.WWW.UNIMUNDI.COM
YAHOO.COM.ZZZZZZ.MORE.INFO.AT.WWW.BEYONDWHOIS.COM
....Whole bunch more