Thread: How to initialize a non blocking socket using only winsock library

Hi, im sorry for asking what must be a very simple question, but i just cant figure out (ive googled and sifted thru msdn) how to set a socket as non blocking. Is it a function which sets it as non blocking or blocking, or is it in a data structure which is used by a function? Im sorry but i just cant figure it out, so if anyone could help me it would be greatly appreciated.

Also, just out of curiosity, is a socket set as blocking/non blocking when the socket is initialized (ie socket is called), or can it be changed, say, in between two recv() calls.

Thx again

Well, i think your talking about what happens with non-blocking sockets once they have been initialized. If you call recv and the call wouldblock, then it returns a blocking error and you must parse that and move on with the program.

When you create a socket it is automatically set to be blocking. If you want to set it to non blocking then you can call fcntl, i.e.

Code:

fcntl(sockfd, F_SETFL, O_NONBLOCK);

however this is something i dont recommend doing as it requires you to continually check the socket and can kill the CPU.

I highly recommend you use the select method which can monitor a set of sockets and when there is an event on one of them you can then determine which one it is and work with it. You can also add a timeout interval on select so if no event is received on the sockets during that time interval then it carries on with program execution.

Let us know if you need any help using select. It is relatively easy.

Hope this helps