Error: Address already in use
I am making a "process monitor" with a web api.
Some times the monitor quit when children still running. 
I found that each child was still keeping the socket opening which the jester listen to.
This cause the next time trying to start the monitor failure.

From linux man page, we should set the socket(fd) with flag: O_CLOEXEC.
Is there any way I can get the underlying socket and set it's flag?