Berkeley description: This is a temporary condition and
later calls to the same routine may complete normally (also known as
EAGAIN error in Berkeley Software Distribution version 4.3)
WinSock description: Same as Berkeley. The socket is
marked as non-blocking (non-blocking operation mode), and the requested
operation is not complete at this time.
operation is underway, but as yet incomplete.
closesocket(): occurs on a non-blocking socket with non-zero timeout
set with SO_LINGER.
The behavior may vary: some WinSocks might complete in background, and
others may require another call to closesocket to complete. Do not set
non-zero timeout on non-blocking sockets to avoid this ambiguity (see
Chapter 9 for more information).
send() or sendto(): out of buffer space, so try again later or wait until
or writefds is set.
all other functions: retry the operation again later
since it cannot be satisfied at this time.