09-ivr-server

09 · Reactive inbound server (IVR / routing)

Beta status: Supported. The CallbackPeer reactive surface is supported. See COMPATIBILITY_MATRIX.md.

Overview

Where StreamPeer is sequential (you call it), CallbackPeer is reactive (it calls you): you register hooks and the library dispatches typed events into them. That's the right model for servers — IVRs, routing front-ends, auto-answer endpoints. This demo wires the builder form with on_incoming, on_established, on_dtmf, and on_ended, and a scripted caller exercises it.

Demo flow

1. server (the IVR, :5120) accepts inbound calls and reacts to DTMF. Press 0 and it would blind-transfer you to an operator.
2. caller (:5121) connects and sends 1, 2, #.
3. The IVR logs each press; the caller hangs up.

Architecture

   caller (:5121) ── INVITE ─▶ IVR server (:5120)
        │  ◀──────── 200 OK ───────  on_incoming → Accept
        │  ── DTMF 1, 2, # ────────▶ on_dtmf hook fires per digit
        │  ── BYE ─────────────────▶ on_ended

Quick start

./run_demo.sh

Or manually:

cargo run --bin server
cargo run --bin caller

Expected output

  [ivr] listening on sip:ivr@127.0.0.1:5120
  [ivr] incoming call from …
  [ivr] ✅ call … established
  [ivr] call … pressed 1
  [caller] ✅ connected to IVR
  [caller] sent DTMF 1

✅ DEMO SUCCESSFUL — IVR reacted to inbound call + DTMF

Beta scope notes

• The example uses the builder closures. For complex servers, implement the CallHandler trait (see the in-crate callback_peer/06_trait_handler), or use the built-in RoutingHandler / QueueHandler.
• Pressing 0 triggers transfer_blind to an operator URI that isn't started in this two-process demo, so the caller only sends 1, 2, #.

Troubleshooting

• Caller can't connect — start the server first; run_demo.sh waits for the IVR's port.

Next steps

• 10-call-center-b2bua — route + bridge across legs.
• In-crate references: callback_peer/ (six numbered handler scenarios).