Thread: Single-threaded Winsock

I made a Socket class that has a "hasData()" function that uses select(). That way a server can loop through the client Socket's, only receiving if there's data to be had, and doesn't get tied up with any one client.

**Note: select() will let you know if a listening socket has clients waiting to connect, so you don't have to block for the accept()'s either.

Not necessarily. This is my code:

Code:

bool hasData(SOCKET sock)
{
	timeval t = {0,0};
	fd_set fds;
	FD_ZERO(&fds);
	FD_SET(sock, &fds);

	return (::select(0, &fds, NULL, NULL, &t) > 0);
}

Then, if sock is a listening socket, hasData() will return true if there is a client waiting to connect, or if it's a normal socket that sends/receives data, it will return true if data is waiting to be received.

Initializeing the timeval to {0,0} means that if there are no sockets with incoming connections/data, select() will return immediately, instead of waiting for a socket to have data.

This is probably not the best way of doing things, but it works and is pretty convenient a lot of the time.

The first argument of select() specifies the highest number of a socket descriptor that will be examined plus one

I don't know about that... Maybe this is only a Windows thing, as you said, but straight from MSDN:

int select (
int nfds,
fd_set FAR * readfds,
fd_set FAR * writefds,
fd_set FAR * exceptfds,
const struct timeval FAR * timeout
);

Parameters
nfds
[in] This parameter is ignored; it is included only for
compatibility with Berkeley sockets.

Well, portability is out of the question for me anyways since I'm doing a Windows app, but I guess it would be good to learn the berkeleian way anyways, just in case I ever change an OS...

Code:

MSG msg;
while(!done)
{
     while(PeekMessage(...))
     {
          (...)
     }
     if(hasData(theSocket))
     {
          recv(theSocket, ...);
          updateProgressBar();
     }
}

any delay in the use of recv would hold up the loop completely, which is also not good.

There would BE no delay with recv(), since recv() doesn't get called unless there's already data to be received.

Ah, riiiiiiiight, I see. I kept thinking that what I was trying to do would cause some sort of blockage because IE gets regularly reduced to a window full of white while its status bar says "Done" when I load a page.

Perhaps it's a Microsoft quirk.

And I like to write code that's broadly compatible with other platforms, Ayebro. You can't get WSAAsync... anywhere else.