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Writng a Java Telnet Client

Posted on 2001-08-01
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Last Modified: 2008-02-01
Hi,
   I am now writing a Java Client Telnet program to telnet to other server. I have new a Socket on the server on Port 23 which is the default telnet port. However, when I run the program:

c:>java JavaTelnet xxx.yyy.com

server is : xxx.yyy.com
server socket connected! Socket[addr=xxx.yyy.com/192.168.1.1.,port=23, localport=1212]

then.. the program keep waiting and has no any reply from the server. Can anyone tell me what have I missed? Thanks!


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

public class JavaTelnet {
    public static void main(String[] args) throws IOException {

          //The args should be the server host name
        Socket telnetSocket = null;
        PrintWriter out = null;
        BufferedReader in = null;
        String host = null;
       
        if (args!=null && args.length>0){
          if (args[0]!=null && !args[0].equals("")){
               host = args[0];
                  try {
                      telnetSocket = new Socket(host, 23);
                      out = new PrintWriter(telnetSocket.getOutputStream(), true);
                      in = new BufferedReader(new InputStreamReader(
                                                  telnetSocket.getInputStream()));
                  } catch (UnknownHostException e) {
                      System.err.println("Don't know about host: " + host + ".");
                      System.exit(1);
                  } catch (IOException e) {
                      System.err.println("Couldn't get I/O for "
                                         + "the connection to: "+ host +".");
                      System.exit(1);
                  }
                  System.out.println("server is : " + host);
                  System.out.println("server socket connected! " + telnetSocket.toString());
                  System.out.println(in.readLine());
                  System.out.println("from server: " + in.readLine());
                 
         
               BufferedReader stdIn = new BufferedReader(
                                             new InputStreamReader(System.in));
               String userInput;
         
               while ((userInput = stdIn.readLine()) != null) {
                   out.println(userInput);
                   System.out.println("telnet: " + in.readLine());
               }
         
               out.close();
               in.close();
               stdIn.close();
               telnetSocket.close();              
          }
        }
    }
}
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Question by:john_law70
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2 Comments
 
LVL 92

Accepted Solution

by:
objects earned 30 total points
ID: 6344059
It's not that simple, read the telnet rfc:

http://www.faqs.org/rfcs/rfc854.html

Here's a telnet client with source:

http://www.mud.de/se/jta/


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LVL 92

Expert Comment

by:objects
ID: 6391338
Thanks for the points and best of luck :)
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