Please describe the problem:
We are writing a modified client (http://warclient.byethost10.com/index.html) of Freeciv open source strategy game and wanted to use glib iochannels for asynchronous server list update. We had some code that worked perfect in linux but didn't work in windows. The glib version we used was 2.12.3. We used g_io_channel_win32_new_socket to create an iochannel from existing winsock socket which was set to nonblocking mode using ioctlsocket. Then we called connect to connect the socket. After that we used g_io_add_watch_full to set a callback for G_IO_ERR | G_IO_HUP | G_IO_OUT. We wanted to use glib iochannel for callbacks, data transfer was done by direct calls to winsock.

The observed problems were:
[1.] In windows, callback got called too early, before FC_CONNECT or FD_WRITE event was dispatched. The GCondition reported was G_IO_OUT. Subsequent calls to send failed with "Write error during send of metaserver request: A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) no address was supplied.". The workaround was to try select in callback and return if socket was not writable. This way callback got called again until select reported socket writable. Download log from http://warclient.byethost10.com/phpBB2/files/finallog_151.zip . The important file is stdout. The socket to watch for is 1464.

g_io_channel_win32_new_socket: sockfd=1464
g_io_win32_sock_create_watch: sock=1464 handle=0x5a4 condition={OUT|ERR|HUP}
g_io_win32_prepare: WSAEventSelect(1464, 0x5a4, {WRITE|CONNECT|CLOSE}
g_io_win32_check: WSAEnumNetworkEvents (1824, 0x71c) revents={} condition={IN|ERR|HUP} events={}
g_io_win32_check: WSAEnumNetworkEvents (1464, 0x5a4) revents={} condition={OUT|ERR|HUP} events={}
g_io_win32_dispatch: pollfd.revents=OUT condition=OUT|ERR|HUP result=OUT

There we can see that we register for WRITE|CONNECT|CLOSE, but no events are received (in events={}) and g_io_win32_dispatch calls our callback with GCondition set to OUT (result=OUT).

In this case, our callback should be called only:
1.) if socket is "valid", connect was called and if FD_CONNECT or FD_WRITE was received after we registered with WSAEventSelect (via glib)
2.) if iochannel was created on a socket that was already connected using winsock functions and last operation didn't result in WSAEWOULDBLOCK (those are send, sendto, WSASend, or WSASendTo). Then we should call the callback with OUT since the socket is writable.

[2.] The 2nd observed problem was with receiving HUP GCondition in our callback. So our application wasn't notified connection was closed and couldnt respond appropriately. The HUP is not sent if events FD_READ and FD_CLOSE are dispatched at the same time. When glib g_io_win32_check discovers there are FD_READ and FD_CLOSE events, it dispatches only IN and not HUP. HUP works properly only if FD_CLOSE event is set after FD_READ was processed by g_io_win32_check. Then IN is dispatched first, and then HUP. The bad behavious is visible in the 1st stdout log.

g_io_win32_check: WSAEnumNetworkEvents (1464, 0x59c) revents={IN} condition={IN|ERR|HUP} events={READ|CLOSE}
g_io_win32_dispatch: pollfd.revents=IN condition=IN|ERR|HUP result=IN

We see FD_READ and FD_CLOSE set in "events={READ|CLOSE}", but g_io_win32_dispatch returns only IN (look for the "result").

The good behaviour is visible in the 2nd stdout log from http://warclient.byethost10.com/phpBB2/files/logs2_111.zip

g_io_win32_check: WSAEnumNetworkEvents (1464, 0x59c) revents={IN} condition={IN|ERR|HUP} events={READ}
g_io_win32_dispatch: pollfd.revents=IN condition=IN|ERR|HUP result=IN
g_io_win32_check: WSAEnumNetworkEvents (1816, 0x714) revents={} condition={IN|ERR|HUP} events={}
g_io_win32_check: WSAEnumNetworkEvents (1464, 0x59c) revents={IN} condition={IN|ERR|HUP} events={CLOSE}
g_io_win32_dispatch: pollfd.revents=HUP condition=IN|ERR|HUP result=HUP

It should be noted that we use IOChannels for callbacks only, writing and reading is done directly via send, recv (winsock), write, read (linux). WSAGetLastError is used to detect errors when using winsock.

FIX:
These bugs were so serious, that we would have to abandon iochannels for windows completely and use WSA functions directly which would introduce mess in the code or use glib threads + blocking sockets. So I spent one afternoon studying the problem and giowin32.c looking for bugs and came with my own patch. The patch can be downloaded from here http://warclient.byethost10.com/phpBB2/files/glib_228.zip

The patch is quite well documented, unclear lines can be discussed here, there is a reason for every line. It fixed both mentioned problems, and might fix the problems that gaim is having too. Some weird code that caused events to stop working totally was commented out. OUT will be dispatched properly even if FD_WRITE or FD_CONNECT isn't dispatched because it was dispatched before (this is safeguarded by using a select in g_io_channel_win32_new_socket, read MSDN, they are dispatched only once when u connect, and then FD_WRITE is dispatched only after reenabling call to send, sendto, WSASend, or WSASendTo) http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winsock/winsock/wsaeventselect_2.asp

I created 2nd bug report since I'm reporting 2 bugs in detail and also supply a fix. We didn't discover any side effects yet, but feel free to test the dlls directly by downloading them from http://warclient.byethost10.com/glib-2.12.3.zip.zip
We use these patched dlls until there is an official fix in glib.


Steps to reproduce:
See above

Actual results:
See above

Expected results:
See above

Does this happen every time?
See above

Other information:
See above