[3.12] gh-112020: Rework socketserver examples to be correct (GH-129741) (#129744)

gh-112020: Rework socketserver examples to be correct.

Outdated code updated, the BaseRequestHandler example is now much more
illustrative instead of the bad idea of a single recv() call for TCP.

tested, they now work.
(cherry picked from commit 78377c788e02e91bf43d290d69317198a2e563fd)

Co-authored-by: Gregory P. Smith <greg@krypto.org>