Socket select() Time Switching?

Question

I have created 6 Sockets and simultaneously listening to all of them using select. I want to find out how much time does the CPU take switching from 1 socket to another. Does anyone know; if not can someone guide me please on how to compute this problem!

Answer 1

I think you may have misunderstood what the select call is actually doing, the man page for select says the following:

Three independent sets of file descriptors are watched. Those listed in readfds will be watched to see if characters become available for reading (more precisely, to see if a read will not block; in particu- lar, a file descriptor is also ready on end-of-file), those in writefds will be watched to see if a write will not block, and those in exceptfds will be watched for exceptions. On exit, the sets are modified in place to indicate which file descriptors actually changed status. Each of the three file descriptor sets may be specified as NULL if no file descriptors are to be watched for the corresponding class of events.

So when your call to select returns what it will tell you is which, if any, of the file descriptors are (in your case) ready to be read from. It's then up to you to decide which to read and how to read it.

If you can I'd reccomend tracking down a copy of Unix Network Programming (by Stevens, Fenner, Rudoff). This will give you all the background information and example C code that you will ever want on network programming.

Or look at the tutorial here