topic Re: How to change telnet client default port? in Operating System - HP-UX

How to change telnet client default port?

Guna_2 — Mon, 25 Jun 2007 05:34:33 GMT

Hi all,

From a hpux box if we issue the command

#telnet hostname

By default it connects to port No 23. I want to configure the telnet command to connect some other port.

How can i do this?

Thanks and Regards
--MGP--

Re: How to change telnet client default port?

Luk Vandenbussche — Mon, 25 Jun 2007 05:42:12 GMT

Change the port number in /etc/services

Re: How to change telnet client default port?

Guna_2 — Mon, 25 Jun 2007 05:50:37 GMT

Hi

If i change the port no in /etc/services. Then my telnet server daemon also will listen only in that new port. I don't want to disturb the telnetd daemon's port.

I want just like, whenever i issue the telnet command it should connect to some other port.

Thanks and Regards
--MGP--

Re: How to change telnet client default port?

Dennis Handly — Mon, 25 Jun 2007 05:50:41 GMT

The syntax for telnet is:
telnet [[options] host [port]]

Re: How to change telnet client default port?

Torsten. — Mon, 25 Jun 2007 05:53:04 GMT

You can do like suggested but why?
This won't make the system more secure.

For more security, disable telnet and use ssh.

Re: How to change telnet client default port?

Guna_2 — Mon, 25 Jun 2007 06:07:01 GMT

Hi dennis,

You are right. But,

I have 2 hpux 11.11 servers.

From server A i am trying to connect server B via telnet

A# telnet B
password:

(logged into the Server B.)

B#netstat -a | grep A
tcp 0 0 B.22 A.58757 ESTABLISHED

The connection has established between the port no. 22.

and in the server B the telnet service itself is disabled in inetd.conf

and in server A the /etc/services the port no specified for telnet is 23.

Then how whenever i issue the command telnet servername it is connecting to 22 port instead of default 23 port?

can anyone please explain me?

Is there any relation between the sshd daemon and this?

Thanks and Regards
--MGP--

Re: How to change telnet client default port?

Luk Vandenbussche — Mon, 25 Jun 2007 06:15:36 GMT

If the connection is made on port 22 (and you didn't change anything to the configuration) then you are connecting through ssh

Re: How to change telnet client default port?

Guna_2 — Mon, 25 Jun 2007 06:27:35 GMT

Hi

Ya all r right.

when i tried stirngs /usr/bin/telnet and /usr/bin/ssh

the content is same.

I think for security purpose some admin has done this.

One more doubt.

In Server B telnet service is disabled in inetd.conf

But in netstat -a | grep LIST output. the telnet port is listening.

tcp 0 0 *.telnet *.* LISTEN

How this is happening?

Thanks and Regards
--MGP--

Re: How to change telnet client default port?

Luk Vandenbussche — Mon, 25 Jun 2007 06:33:32 GMT

Perhaps

/usr/lbin/telnetd and /usr/sbin/sshd are also the same.

I find it strange to copy ssh over telnet

Re: How to change telnet client default port?

Sandman! — Mon, 25 Jun 2007 06:35:06 GMT

You need to recycle inetd for the changes made to /etc/inetd.conf to take effect. Most likely someone commented out telnetd in the /etc/inetd.conf file but forgot to recycle the inetd daemon.

Re: How to change telnet client default port?

Dennis Handly — Tue, 26 Jun 2007 00:29:20 GMT

As Luk says, it comes from /etc/services.

telnet calls getservbyname("telnet", "tcp")