5 POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/errno.html}
9 Portability problems fixed by Gnulib:
13 Portability problems not fixed by Gnulib:
16 On Windows, the socket functions don't set @code{errno}; their error code is
17 available through @code{WSAGetLastError()} instead.