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recvfrom() problem

I have an application using UDP under BSD, in which I see some strange behaviors.

When calling recvfrom(), my "struct sockaddr *from" (see man page) doesn't always get filled out. It seems to be completely random if it works or not between different test-runs. On several occasions I've had it working on one test-run, then fail on the next one, only quitting and restarting the app in between (same build).

recvfrom() never returns an error (-1 and setting the errno variable), it always returns the number of bytes received, and the transfered data is correct. The only thing not working is that "struct sockaddr *from" doesn't get filled out.

I use inet_ntoa(from.sin_addr) to get the ip of the machine that sent the message, and it comes out as 0.0.0.0.

The strange thing is that it sometimes work. I am testing over a cross-over cable + two machines, with the ip's 192.168.0.2 and 192.168.0.3. These are the ip's I get from inet_ntoa() when it works.

Running in a debugger, the value from the ip inside of the struct sockaddr doesn't even get touched when recvfrom() is called.

Can anyone explain this behavior?

Thanks a lot for any help!

- Nils
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