Hi Alistair,
I haven't thought of this. I'm not that familiar with linux syscalls.
Not specifying a default protocol makes getsockopt return wrong value with level = SOL_SOCKET and optname = SO_PROTOCOL_INFOW. It leads to a "fixme:winsock:WS_EnterSingleProtocolW unknown Protocol" and an invalid returned WSAPROTOCOL_INFOW in optval but i guess this issue needs to be fixed in the server call in ws_protocol_info then.
Regards Robin