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serversdownandClaude Opus 5 704cd7b111 feat(bridges): mm_probe -- tell apart the four faults THOR calls "disconnected"
THOR reports every failed connection as "disconnected" and nothing more.  That
one word covers at least four distinct faults with four different fixes, and
telling them apart is the difference between a modem reboot and a site visit.
Nobody had a way to do that during the 2026-09-22 outage, which is the actual gap
that incident exposed -- not a missing THOR feature, but a missing tool.

    connection refused    something answered and said no -- wrong port, or the
                          modem refusing a further session
    connect timed out     nothing answered -- trusted-IP whitelist, firewall, or
                          the modem is off the network.  A whitelist DISCARDS
                          rather than refuses, so this is its signature
    connected, no reply   the MODEM answered but the unit did not.  TCP is fine;
                          the modem is not forwarding to serial.  This is what a
                          wedged transparent-TCP session looks like, and it is
                          the case THOR cannot distinguish from the others
    replied               the unit is alive; the fault is upstream software

Each verdict prints what to try next.  The no-reply case points at ACEmanager's
TCP Idle Timeout first, since a stale session holds a single-slot modem's only
connection until that timeout frees it.

--slots N opens N simultaneous connections and reports how many the far end
accepts, which directly tests the single-session hypothesis against a real modem.

Read-only throughout: POLL, SERIAL and the 0x49 state read -- the same three
commands THOR's own connection check uses.  Sends the correct per-SUB data
offsets (POLL 0x0030, SERIAL 0x000A, 0x49 0xFFFF); offset 0 returns only the
short probe reply.

Works for both series and says which answered: a Series III reply opens DLE STX,
a Micromate reply opens with a bare STX.

Verified against UM12947 through the bench relay, and against a closed port for
the refused path.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ru8Lg9HkkYvX9VWWo65SmL
2026-09-25 14:50:44 -04:00
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