emulation with socket: fix nasty delay
properly check all return values (read() returning 0 indicates closed peer)
ClientContext::state() triggers read() to check for closed peer
uart emulation on tty: add cmdline -b debug option to disable raw tty
hide annoying MOCK messages, add cmdline -v option to show them
uart emulation on tty: check more return values
emulation on host: tcp/udp port shifting: new cmdline -s(port Shift) option
