I'm investigating some issues with winsock 10055 errors on a chain of custom applications (some of which we control, some not) and was hoping to get some advice on techniques to troubleshoot the problem.

No buffer space available.
    An operation on a socket could not be performed because the system 
    lacked sufficient buffer space or because a queue was full.

From research, non-paged pool and ports seem to be the only resources which can cause this error. Is there another resource which might cause 10055 errors?

Currently, we have perfmon counters setup on the applications and non-paged pool usage looks low in most circumstances. Open TCP connections looks low and I am unaware of another way to monitor ports.

Since it only happens in production, we are unable to use more invasive counters.

Is there some other tool or procedure you would recommend to diagnose which application is causing the issue?