Damian
Tue Sep 09 17:11:05 CDT 2003
Hi,
When you open a telnet session to a TCP port, such as 25 or 80, you are in
fact talking to that service that is running on the remote server through a
clear TCP session.
You will need to know the proper protocol in order to type the commands that
would be understood by the remote server, such as a MAIL FROM command when
connecting to an SMTP server or a GET command when connecting to a Web
Server (HTTP Protocol). You would also need to proper commands to end the
session and you will not be able to use backspace, when you type a
character, the information is sent to the remote server immediately, so
there is no way of recalling that.
The telnet commands you are referring to are only to be used while the
telnet client is not connected to anything, is just for local
configuration/use.
If you want to enable Echo to see what you are typing, just open Telnet
(without making a connection), and then type SET LOCAL_ECHO .
You can use telnet to test connectivity and to isolate potential points of
failure. By reducing the number of layers and the complexity of the tests,
you can get closer to identifying the cause of the problem more quickly. Can
we telnet from within the LAN? Can we telnet from the server to itself? Can
we telnet from the other side of the router? And so on.
We usually use telnet to test connectivity to any port (besides knowing the
protocol or not), but especially for SMTP, POP and IMAP connectivity and
SMTP relay issues.
189326 XADM: Verifying Basic IMAP Connectivity Using Telnet
http://support.microsoft.com/?id=189326
165186 XFOR: Verifying Basic POP3 Connectivity Using Telnet
http://support.microsoft.com/?id=165186
153119 XFOR: Telnet to Port 25 of IMC to Test IMC Communication
http://support.microsoft.com/?id=153119
Regards,
--
Damian N. Leibaschoff, MS IST, MCSE
Microsoft Corporation
Get Secure! - www.microsoft.com/security
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"joe" <joe@joe.com> wrote in message
news:0ca301c37714$c41222c0$a001280a@phx.gbl...
> Hi,
> I recently had to do some network troubleshooting and
> learned a little about telnet (sorry if my questions are
> dumb, I'm having a little trouble figuring out some basics)
>
> I was given this link to help test if port 25 was open.
>
http://support.microsoft.com/default.aspx?scid=kb;en-
> us;153119
>
> I was able to send an email via telnet but have a couple
> fo questions. After telnetting to port 25, I noticed the
> telnet commands (close, set, etc) no longer worked. Why?
> Is this because once I entered the port I was no longer
> telnetting but was using the smtp protocol? I also
> noticed I could not see what I was typing (I was using the
> command shell). Is there away to toggle some function so
> I can see the text?
>
> If I telnetted to port 80, nothing would happen until I
> hit enter twice, this would cause the delivery of a 404
> html page (displayed in the command shell). Once again,
> after telnetting to port 80, none of the telnet commands
> worked. So obviously I was connecting to the web server
> but it's not clear what was going on.
>
> If I went to a known closed port, I would get a could not
> connect message. (which is good)
>
> I'm just confused on what you can do via telnet besides
> access open ports. I have a copy of basic commands etc
> but I'm missign a few fundamentals.
>
> Any explination on what was happening would be very
> benificial.
>
> Thanks