Question

For every single tutorials and examples I have seen on the internet for Linux/Unix socket tutorials, the server side code always involves an infinite loop that checks for client connection every single time.
Example:

http://www.thegeekstuff.com/2011/12/c-socket-programming/

http://tldp.org/LDP/LG/issue74/tougher.html#3.2

Is there a more efficient way to structure the server side code so that it does not involve an infinite loop, or code the infinite loop in a way that it will take up less system resource?

Answer 1

the infinite loop in those examples is already efficient. the call to accept() is a blocking call: the function does not return until there is a client connecting to the server. code execution for the thread which called the accept() function is halted, and does not take any processing power.

think of accept() as a call to join() or like a wait on a mutex/lock/semaphore.

of course, there are many other ways to handle incoming connection, but those other ways deal with the blocking nature of accept(). this function is difficult to cancel, so there exists non-blocking alternatives which will allow the server to perform other actions while waiting for an incoming connection. one such alternative is using select(). other alternatives are less portable as they involve low-level operating system calls to signal the connection through a callback function, an event or any other asynchronous mechanism handled by the operating system…