Telnet execution using Java

[Nizamuddin Shaikh]

Hi Everyone!

I am trying to execute a statement to retrieve some information from remote Linux server using telnet command. I am able to connect to remote server but unable to pass next statement to retrieve information.
I am posting my code (after replacing sensitive data)

import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.charset.StandardCharsets;

import com.jcraft.jsch.Channel;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;
import com.jcraft.jsch.ChannelExec;

public class RealtimeYTelnet {

		public static void main(String[] args) {
		    String host="1.2.3.4";//this is remote server - replaced
		    String user="username";
		    String password="password";
		    String command1="telnet localhost 7777";
		    String command2 = "how are you";
		    try{
		    	ByteArrayInputStream stream = new ByteArrayInputStream(command2 .getBytes(StandardCharsets.UTF_8));
		    	java.util.Properties config = new java.util.Properties(); 
		    	config.put("StrictHostKeyChecking", "no");
		    	JSch jsch = new JSch();
		    	Session session=jsch.getSession(user, host, 22);
		    	session.setPassword(password);
		    	session.setConfig(config);
		    	session.connect();
		    	System.out.println("Connected");
		    	
		    	Channel channel=session.openChannel("exec");
		        ((ChannelExec)channel).setCommand(command1);
		        
		        channel.setInputStream(null);
		        ((ChannelExec)channel).setErrStream(System.err);		        
		        channel.connect();
		        channel.setInputStream(stream);
		        InputStream in=channel.getInputStream();
		        
		        byte[] tmp=new byte[1024];
		        while(true){
		          while(in.available()>0){
		            int i=in.read(tmp,0,1);
		            if(i<0)break;
		            System.out.print(new String(tmp, 0, i));
		          }
		          
		          if(channel.isClosed()){
		            System.out.println("exit-status: "+channel.getExitStatus());
		            break;
		          }
		          try{Thread.sleep(1000);}catch(Exception ee){}
		        }
		        
		        channel.disconnect();
		        session.disconnect();
		        System.out.println("DONE");
		    }catch(Exception e){
		    	e.printStackTrace();
		    }

		}

}

However the response from the remote server should be "I am fine"

[Nizamuddin Shaikh]

In short! Can I combine two commands command1 and command2 to get the output?

[Nizamuddin Shaikh]

If I combine command1 and command2 by using echo "How are you \n" | telnet localhost 7777. I am getting "Connection closed by Foreign host"

[Tim Moores]

Does JSch support the Telnet protocol? I thought it was an SSH library.

The Apache Commons Net library includes a Telnet client.

[Nizamuddin Shaikh]

Yes it does support telnet.

[Nizamuddin Shaikh]

I was able to fix my problem. Here's the solution that worked for me. command ="{ echo 'How are you'; sleep 1; } | telnet localhost 7777"

[Nizamuddin Shaikh]

Tim Moores wrote:
The Apache Commons Net library includes a Telnet client.

I will study about Apache Commons Net library. Thank you