I ran into a bug in that area a while back. Our development environment has a binding to Winsock32.dll for socket stuff, and as it turns out the bindings were written so long ago that many of the return values are specced to be 16-bit ints. As a result, our application would work fine almost all of the time, but fail mysteriously with "socket operation on non-socket" after about 8000 sockets have been opened. As I understand it 8000 is because file descriptors are a kind of bump-the-pointer scheme internally and pointers are 8 bytes wide on 64-bit platform.