Portability problems fixed by Gnulib:
@itemize
@item
+This function has the return type @code{int} instead of @code{ssize_t}
+on some platforms:
+OSF/1 5.1.
+@item
On Windows platforms (excluding Cygwin), error codes for @code{sendto}
are not placed in @code{errno}, and @code{WSAGetLastError} must be
used instead.