KISS modem over TCP (meshtasticd raw modem mode)

[A13xB0]

Warning

Awaiting upstream review of meshtastic/firmware#11863

KISS modem over TCP, for meshtasticd's raw modem mode

A kiss radio's device can now be tcp://host:port. This lets RepeaterTastic use a Linux LoRa HAT (SPI) or CH341 USB stick through meshtasticd's raw modem mode, which serves the radio with the same Mesh KISS v2 protocol, so no Heltec/RAK board is needed.

radio:
    driver: kiss
    device: tcp://127.0.0.1:4405

It needs a patched meshtasticd for now: the raw-modem branch of A13xB0/firmware, until it is proposed and merged upstream. This PR is separate from the native SPI driver (#3) and based on main only.

Changes

• internal/radio/kiss: tcp:// devices connect with a net.Dialer (connect timeout DialTimeout, default 5s; TCP keepalives; no Nagle) instead of opening a serial port. They reconnect and re-apply the config the same way as serial. TCPAddr() parses and validates the address. Tests: the fake modem is served over a loopback TCP listener, covering handshake, configure, RX with escaping and RxMeta, TX, and a meshtasticd restart (drop, refused dials, reconnect, config re-applied). Address parsing is tested too.
• internal/config: a malformed tcp:// device is rejected. Two radios on the same tcp:// address are refused, with host names compared case-insensitively, because meshtasticd serves one client at a time.
• kisstool: --dev tcp://host:port works (help text updated).
• Web GUI: the setup Test modem probe accepts tcp:// devices. Before a password is set it only dials loopback addresses, so the unauthenticated probe can't be pointed at other hosts. The UI is unchanged and needs no rebuild.
• Docs: new docs/meshtasticd-raw-modem.md covers building and enabling the fork, the config.yaml snippet, the RepeaterTastic config, and caveats: no auth on the port, one client, Docker networking, tx_enabled and regional power limits. It is linked from the README docs table, docs/configuration.md and docs/hardware.md.

Testing

• go vet ./... and go test ./... pass.
• Tested against the patched meshtasticd on SimRadio in Docker (meshtasticd -s --raw-modem 4405):
  • kisstool info --dev tcp://127.0.0.1:… reports meshtasticd sim, Mesh KISS v2, patched;
  • kisstool listen configures EU_868 LongFast and reads it back;
  • the daemon with device: tcp://… opens the radio and logs radio configured.
• Not tested on real RF hardware; there was no radio. SimRadio can't transmit, so send-text gets TxDone failure there as expected.

🤖 Generated with Claude Code

https://claude.ai/code/session_01SJZ75CWob1eMXeTa8Q2nLc