There don't seem to be any unit tests for the socket handling elements. As
I am about to attempt some refactorings I've added some basic tests which
exercise some of the happy-paths in tcpclientsrc, tcpserversrc,
tcpserversink and tcpclientsink. They should let me know if I've caused
serious breakage.
They are far from exhaustive but are sufficient for me to have caught a few
memory-leaks in the existing code.
https://bugzilla.gnome.org/show_bug.cgi?id=739544
