Playing with low-level networking code in several languages on several platforms, I followed this example from the Apple developer forum to get a Network.framework example working.
It works great but the app never exits back to the commandline due to using dispatch_main().
The documentation is very sparse, examples are not common, and tutorials barely exist at all. Hunting around the internet all I find is mentions that this never returns, but I can't find anything about how to break out of it when I actually want to return.
I'm assuming this relies on background knowledge of GCD (grand central dispatch) and runloops and such that I don't have and that isn't easy to find. Perhaps it's only relevant for a commandline app but most Apple code is for GUI?
So is there a way to break out of/return from the loop/thread/etc that dispatch_main puts me in? Or is there some alternative API or method other than dispatch_main that you're supposed to use when you intend to return?
For this, you probably want to use the C function void exit(int status); See the output of man 3 exit. This will run various standard C cleanup processes and cause your process to exit cleanly with the status code you call it with.
What's perhaps more interesting is the question: "How does your process know when to call exit()?" Is it going to receive a network payload that tells it when to quit? Will you send it a UNIX SIGTERM signal? (If this feels like a misuse of SIGTERM to you, you could consider using SIGUSR1 or SIGUSR2.) GCD has signal handling capabilities built in (see DispatchSource.makeSignalSource here). To be more explicit, you could add a GCD signal handler for SIGTERM do whatever other cleanup you need to do, and then call exit() at the end of the handler block, and that should do the trick.
Hope that helps!