select(), sockets, and writefds...

[iago]

I was wondering if it's ever possible for sockets to block writing.  When implement select(), waiting to send packets is really annoying, since I don't normally wait on writefds, I have to adds it to a queue, set a flag, wake up the select() call, and tell it to wait for writing.  Is this necessary for sockets? Or is that only designed for other select() uses?

Thanks

[Skywing]

Yes, sockets will block on send() if the underlying send buffer is filled and the socket is operating in blocking mode.  As far as I know, there is no standard way to make sockets block on send and not recv.

If you are targetting Win32, I strongly recommend that you use overlapped I/O instead of conventional, BSD-compatible socket APIs.

[iago]

I'm targetting Linux, actually, so I'm using the BSD interface. 

Thanks for the response, though, I'll find a way to implement it properly!

[Skywing]

I'm targetting Linux, actually, so I'm using the BSD interface. 

Thanks for the response, though, I'll find a way to implement it properly!

I would recommend just building a queue of send requests and then transferring as much of them as you can at once with an iovec send when writing is reenabled on the socket.