Question

I would like to know if the following scenario is real?!

1. select() (RD) on non-blocking TCP socket says that the socket is ready
2. following recv() would return EWOULDBLOCK despite the call to select()

Answer 1

I am aware of an error in a popular desktop operating where O_NONBLOCK TCP sockets, particularly those running over the loopback interface, can sometimes return EAGAIN from recv() after select() reports the socket is ready for reading. In my case, this happens after the other side half-closes the sending stream.

For more details, see the source code for t_nx.ml in the NX library of my OCaml Network Application Environment distribution. (link)