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From: lyndon@cs.athabascau.ca (Lyndon Nerenberg)
Newsgroups: comp.protocols.tcp-ip.domains
Subject: Re: problems with nsfnet-relay.ac.uk
Message-ID: <729@aupaircs.athabascau.ca>
Date: 8 Mar 91 01:05:14 GMT
References: <1991Feb22.181958.14608@ns.uoregon.edu> <75539@bu.edu.bu.edu> <1991Feb26.192433.25943@nstn.ns.ca>
Organization: Athabasca University
Lines: 33

daniel@nstn.ns.ca (Daniel MacKay) writes:

>I have a little problem with the above: 

>	owl% telnet nsfnet-relay.ac.uk 25
>	Trying 128.86.8.6 ...
>	telnet: connect to address 128.86.8.6: Connection timed out

>There's no one listening on the SMTP port!  No, it's not a connectivity 
>problem!

Wrong. If there is no process listening on the port, telnet would say
"connection refused," not "connection timed out." Example:

% telnet annex01 smtp
Trying 131.232.3.5 ...
telnet: connect: Connection refused
telnet> 

Needless to say, our terminal servers don't speak smtp :-)

If you try to connect to a port that has no listener, you will get back an
ICMP_UNREACH_PORT from the host. This generates the message above. The
"timed out" message indicates no response whatsoever was received. It could
be that the ICMP_UNREACH_PORT did not make it back, generating the "timed out"
message, but that's highly unlikely since you were able to telnet sucessfully
to the telnet port.

-- 
    Lyndon Nerenberg  VE6BBM / Computing Services / Athabasca University
           atha!cs.athabascau.ca!lyndon || lyndon@cs.athabascau.ca
                    Packet: ve6bbm@ve6bbm.ab.can.noam
      The only thing open about OSF is their mouth.  --Chuck Musciano