XSIP

Stateful SIP protocol engine for the Xirsys Elixir stack.

Updated from an earlier Xirsys SIP implementation; released for public use.

Real-time voice and video over SIP needs more than parsing messages: requests must match transactions, retransmit on UDP, form dialogs after INVITE, and route BYE/REGISTER/OPTIONS to your application logic. XSIP is a UA-oriented engine that handles that state machine on top of xmedialib wire codec. You bring transport (UDP, TCP, WebSocket framing) via XSIP.Transport. INVITE SDP answers delegate to xsdp through XSIP.SDP.

RFCs

RFC 3261 -- SIP core (messages, transactions, dialogs)
RFC 6026 -- server INVITE accepted state / Timer L
RFC 5626 -- Outbound flow binding (minimal ob= support)
RFC 3264 -- SDP offer/answer (via XSIP.SDP / xsdp)
RFC 7118 -- SIP over WebSocket (host transport concern)

Scope

xsip owns transactions, dialogs, TU dispatch, and method features on top of xmedialib (XMediaLib.SIP codec). I/O is bring-your-own via XSIP.Transport.

This is a UA-oriented engine for the paths listed below, not a claim of full RFC 3261 (or related) conformance.

Supported today (implemented and exercised)

Area	Notes
Typed headers + `XSIP.Message`	Built on `XMediaLib.SIP`; unit-tested round-trips
BYO `XSIP.Transport`	`XSIP.Transport.Mock` for tests
INVITE / non-INVITE client and server transactions	`incoming/4`, `respond/2`, `send_request/5`; timers and retransmit paths in `mix test`
CANCEL matching	Matches INVITE; feature responds `487` while early
Non-2xx ACK absorption	Unit-tested on the INVITE server transaction
RFC 6026 accepted state	2xx moves server INVITE to accepted with Timer L; covered by dialog/2xx flows, not a dedicated Timer L assertion
Dialogs + TU	Out-of-dialog OPTIONS, REGISTER, INVITE; in-dialog BYE
REGISTER Contact echo	200 echoes request Contact(s)
Minimal RFC 5626	`Contactob=` (or app `flow_token`) binds in `XSIP.Outbound.Store`; reconnect reuses the token
`XSIP.App` callbacks	Host registrar / invite policy hooks
Telemetry	Transaction/dialog start-stop and incoming errors

Reference host and SIP.js client (separate repos) exercise the wire happy paths: OPTIONS, REGISTER (incl. unregister), INVITE/ACK/BYE, CANCEL/487, reject/486, Outbound ob= reconnect, unknown method/405, and SIP over WebSocket (RFC 7118) plus UDP/TCP framing in the demo.

Not claimed

Full RFC 3261 UA or proxy compliance (digest, forking, Record-Route, merge detection, re-INVITE, overlapping transactions, and most edge cases)
Full RFC 5626 (keepalives, reg-id / +sip.instance edge recovery, Path)
RFC 3262 PRACK, 3428 MESSAGE, 3515 REFER, 6665 SUBSCRIBE/NOTIFY, 3903 PUBLISH, 3326 Reason, 3327 Path, 5954 IPv6 comparison as product features (some header type stubs exist; no feature/tests)

Usage

# config :xsip, app: MyApp.SIPHandler

# Adapter after framing:
XSIP.incoming(raw, MyTransport, conn, peer)

Installation

def deps do
  [
    {:xsip, "~> 0.1.0"},
    {:xmedialib, "~> 0.3.0"},
    {:xsdp, "~> 0.1.0"}
  ]
end

Contact

For questions or suggestions, email experts@xirsys.com

Copyright

XSIP is licensed by Xirsys, with permission, under the Apache License Version 2.0. See LICENSE for the full license text.