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Re: g_io_channel_win32_poll() Problem on Windows




On 7/27/2017 2:56 PM, LRN wrote:
> On 7/27/2017 2:06 PM, Faik wrote:
> 
>> As you might guess, in  arv_gv_discover_socket_list_new() function,  GPollFDs
>> are created and in _discover() function, a broadcast message is sent and then
>>  polled for reply. but no luck, still in _discover(), it time outs.  By the
>> way, in Linux, the same application works smootly.
>> I also checked the discovery packet was actually emitted, and I saw a camera
>> discovery ack packet coming to my network adapter via WireShark.
> Portable I/O is tricky. If i were in your place, i would write the simplest
> possible code that does this thing (creates a socket, sends a broadcast
> message, then waits for a reply) using W32 socket API only. Once *that* works,
> figure out what glib is doing differently. Since you're providing the socket
> object to glib, at least socket creation part is already in your hands. IIRC,
> glib calls WSACreateEvent() to create an event handle, then binds it to the
> socket using WSAEventSelect(), then just waits on the event handle using
> conventional WaitForMultipleObjects...() (in your case WaitForSingleObject
> would probably be enough). Once it indicates that the event is set, glib calls
> WSAEnumNetworkEvents () to see which socket events happened.
> 

After trying this myself (for unrelated reasons), i found that *only*
giochannel GSource does WSAEventSelect() on a socket event (in
g_io_win32_prepare()) to bind it to an event handle, which can then be polled.
If you are not using a main loop (and GSource), then this doesn't happen, and
the events you feed to g_poll() are completely inert.

Thus, apart from creating sockets yourself, you should also call call
WSAEventSelect(). It might be possible to offload this to glib by pretending to
be a main loop, but driving stuff manually, but i haven't checked that yet.

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