[clug-talk] nasty problem

[Robert Lewko]

Hi guys:

I have a program that sends UDP messages to its server.  Its been working
just fine for about a week since I delivered it.  At about 2:00pm. my client
phoned me to say that the server wasn't working.  When I looked at the
software (putting fprintf''s into it) I could see that it was processing the
packets that it receives and sending the correct data back.  I can ssh into
the server and on both the server and the firewall I can use tcpdump to see
the packet coming in and the packet leaving the server then making its way
out of the firewall.  However, ethereal does not see the packet return to
the client.  This affects me at home (shaw) and my client at his work site
(telus).

One other thing.  For brief periods this afternoon I was getting packets
through without making any changes either to the code, the server or the
client machines.

I am using UDP because the client is using a satellite modem.  The server
uses UDP port 9608.  When the server gets a packet it just gets the source
address and returns the response packet to the sender.  Like I said I have
had no problem with that port both while I have been developing the code and
for the last week until this afternoon.

All the TCP stuff works - ssh, http, https, etc.  Does anyone know how to
diagnose this?
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