Zebediah Figura (@zfigura) commented about dlls/ntdll/unix/socket.c:
{ ULONG_PTR information;
status = try_send( fd, async );
if (protocol == IPPROTO_UDP && async->addr && sockaddr_get_port(async->addr, async->addr_len) == 0 )
The protocol that the server returned is in WS form, so this should be WS_IPPROTO_UDP.