Programming

I'm programming in C with lots of sockets, (asynchronous handling), and for a while it goes ok, but after a while it starts to hang, or not get complete connections anymore.

checking my router, i see that i get nat tables overflow and even my DNS cacher seems to be having serious issues...

I'm wondering if there are limits, or conventional rules that apply to the number of open sockets, or something like that. (currently i've set this to 200, and now i don't get that much of problems, but after a while it does get problematic.)

Maybe i'm not shutting them down properly? (close() should be sufficient? no?) Is there a way to test that? (could i test this with periodically checking netstat? or some easier way?)

Does anyone have a suggestion or some info on this officious rules about max connections?


thanks for the help, in advance.

You have some threaded app that has lots of open sockets?

How are you assigning port numbers?

oh, it's not threaded, it's a single thread that uses non-blocking and select to find out if something is to be done.

I'm not tracking port numbers at all. I'm just accepting TCP connections and connecting TCP connections. do i need to do something with port numbers? all the TCP connections have a different fd, so that's not really a problem, is it?

i did make an eventing structure that holds the addrinfo and fd and other stuff

Okay. There is a limit to the number of open "fd" file descriptors that a process can have. What closes those file descriptors?

If your process is hanging it has to have reached some resource limit. Or there is a race condition.

There is getrusage()/getrlimit() - they let you track and report all of the resources the process is using. I would suggest instrumenting your code with that, have it report all of the resources getrusage will show on your system - write it to a file with timestamps for each entry.

Start there.

thanks, that's exactly the sort of thing i was looking for, you've helped me a great deal. i'll post some results later on!