[NET-608] Exception when using addProtocolCommandListener with library org.apache.commons.net.telnet.TelnetClient

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Not A Problem
• Affects Version/s: 3.5
• Component/s: Telnet
• Labels: newbie

Environment

Windows 7, Java JDK 1.8,

• Assignee: Unassigned
• Reporter: Anthony Kearns
• Created: 03/Jan/17 23:48
• Updated: 07/Feb/17 19:35
• Resolved: 07/Feb/17 19:35

Description

According to the API documentation for WhoisClient and FTPClient these commands appear to support inherited functionality of addProtocolCommandListener.

However, when i used this as follows....i get exceptions raised for TelnetClient and WhoisClient but not the FTPClient.

Is this a bug or as designed? Or am I missing something ?

import org.apache.commons.net.*;
import org.apache.commons.net.ProtocolCommandListener;
import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.telnet.TelnetClient;
import org.apache.commons.net.whois.WhoisClient;
import java.io.PrintWriter;

public class WhoisExample
{
public static void main(String args[])
{
try

{ WhoisClient whoisClient = new WhoisClient(); whoisClient.addProtocolCommandListener(new PrintCommandListener(new PrintWriter(System.out))); }

catch(Exception e)

{ System.out.println("whois client exception" + e); }

try

{ TelnetClient telnetClient = new TelnetClient(); telnetClient.addProtocolCommandListener(new PrintCommandListener(new PrintWriter(System.out))); }

catch(Exception e)

{ System.out.println("telnet client exception" + e); }

try

{ FTPClient ftpClient = new FTPClient(); ftpClient.addProtocolCommandListener(new PrintCommandListener(new PrintWriter(System.out))); System.out.println("no ftp client exception here !"); }

catch(Exception e)

{ System.out.println("ftp client exception" + e); }

}
}

I get the following exception....

Caught: java.lang.NullPointerException Disconnected from the target VM, address: '127.0.0.1:3140', transport: 'socket' java.lang.NullPointerException at org.apache.commons.net.SocketClient.addProtocolCommandListener(SocketClient.java:772) at org.apache.commons.net.SocketClient$addProtocolCommandListener.call(Unknown Source)