Re: determine if TCP or UDP port is working properly?

From: Steven L Umbach (n9rou_at_n0-spam-for-me-comcast.net)
Date: 08/25/04 

Date: Wed, 25 Aug 2004 22:35:44 GMT

For tcp you can try to telnet to the port on the other end as in [ telnet
212.212.212.212 80 ] which would try to telnet to port 80 on that IP address. You
would probably not get a connection but just a blinking cursor. However if the port
is not available telnet request will say "connection failed".

Other ways are to try a network scanner that can scan tcp and udp such as Superscan4
though you may have to configure the udp scan to use data+ICMP for udp scan type
which is not the default. The best way would be to use a packet sniffer like the free
Ethereal on client and server to see what packets are being send and received on each
end of the connection. Of course Ethereal can pick up thousands of packets in a
minute however it has easy to configure capture filters that would allow you to
capture traffic to and from only certain IP address. --- Steve

http://www.ethereal.com/

"Les Caudle" <very@tiredofspam.com> wrote in message
news:gq0qi09k5qvvlnuqqv5qts3j6af2cshoe2@4ax.com...
> I've been trying to diagnose a connectivity problem thru a certain port. The
> connection is traversing thru a proxy and a few other devices - and I can ping
> it from a midpoint - but ICMP is not setup to pass all the way thru.
>
> It would be nice to have some software I could run on one side that would answer
> on a certain port for TCP or UDP - and software on the other side to try to
> communicate using that port. Something very forgiving that would give me some
> info on whether the connection is making it at all - or is just very poor.
>
> Is there some software I can run at both ends to test for a single TCP or UDP
> port?
> --
> Thanks in advance, Les Caudle

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