RuboCop: don’t ignore long methods
Server::UDP#run_loop: close the socket only if it exists
Logging: combine Server::TCP connect and receive loggings
Server::TCP: these are actually private
factor out Server::Sock
factor out Server::{TCP,UDP}#wait_till_started
Logging: hook to Server::Sock
make Logging a module and rename .new to .log_to
bin/kamerling: log to $stdout by default