THOR gives almost no visibility into a connection: a refresh button, two poll
intervals, and no way to see whether a check succeeded, timed out, or was never
attempted. When a unit "won't stay connected" there is nothing to look at. This
sits where the cellular modem would and answers that directly.
Over socat -x it adds the two things that were missing:
* A READABLE LOG. Frames are decoded and timestamped as they pass --
"THOR->unit POLL (21 B)" rather than hex -- so THOR's polling cadence, and
its silences, are visible. Raw .bin pairs are still written alongside and
load straight into scratch/mm_frame_parse.py.
* FAULT INJECTION, via a control file read on the fly:
pass normal relay
blackhole TCP stays up, bytes are swallowed
drop close the connection abruptly
delay:N forward N seconds late, both directions
onewaydev THOR->unit passes, unit->THOR is swallowed
`blackhole` is the point of the exercise. It reproduces the classic cellular
failure -- socket open at both ends, nothing crossing -- which a real cell link
will not do on cue. THOR was observed last night holding one TCP connection for
17 minutes (00:30 to 00:47), so if the link dies silently the OS will not tell it
for roughly the default keepalive, ~2 hours. That is a candidate explanation for
"refresh does nothing and only a restart helps", and this makes it testable
rather than speculative.
No pyserial: the port is driven through stdlib termios. The bench hosts are
whatever is to hand and requiring a pip install on someone else's machine is a
poor trade for ~30 lines. Deployed and verified on mint-mac (Python 3.12, no
third-party modules) against UM12947 -- a POLL round-trips and decodes.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ru8Lg9HkkYvX9VWWo65SmL
