telnet on local LAN question

[Craig White]

On Thu, 2011-08-18 at 20:15 -0700, Paul Allen Newell wrote:
> Oh ... it may be clear to you and others that are familiar with this
> but 
> I didn't know ... I just thought I could run telnet and give it a
> port 
> number to use. I was aware that some ports may not like it (as I 
> discovered with telnet <name> 22), but this is my first round of
> dealing 
> with ports and I cannot begin to tell you how appreciative I am that
> the 
> replies I am getting are longer rather than shorter to make sure I
> can 
> understand the "why" of the suggstions. 
----
of course - you have it right.

telnet is simply an application that opens an interactive TCP based
session.

telnet $SOME_HOST 25 is simply opening a TCP session on $SOME_HOST on
the well-known port 25 (SMTP) and is an excellent way of seeing if the
host is responding (is the smtp daemon listening?), seeing how it
responds and possibly even sending e-mail. I commonly do this for a
number of daemons including imap (143), http (80) and others.

Of course a telnet server would generally use the well-known TCP port 23
but generally usage of this is discouraged since ssh is common and
encrypted and telnet server is an unencrypted connection.

Craig


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