05-blind-transfer

05 · Blind transfer (REFER)

Beta status: Supported. REFER (RFC 3515) + NOTIFY transfer progress are interop-tested. See COMPATIBILITY_MATRIX.md.

Overview

A three-party blind transfer: Alice calls Bob; Bob blind-transfers her to Charlie; Alice ends up talking to Charlie. "Blind" means Bob transfers without first talking to Charlie (contrast with 06-attended-transfer).

Bob uses transfer_blind_and_wait, which sends the REFER and blocks until the transfer lifecycle resolves. Alice drives the completion explicitly: on Event::ReferReceived she hangs up with Bob and calls the REFER target.

Demo flow

1. Alice (:5060) calls Bob (:5061); Bob answers.
2. After a moment Bob calls transfer_blind_and_wait("sip:charlie@…") → REFER.
3. Alice receives ReferReceived, hangs up with Bob, and calls Charlie (:5062).
4. Charlie (already waiting) answers; Alice ↔ Charlie is up. Everyone winds down.

Architecture

   Alice (:5060) ── INVITE ─▶ Bob (:5061)
        │  ◀──── REFER (Refer-To: Charlie) ───┘
        │ hangup Bob
        └──── INVITE ─▶ Charlie (:5062)  ✅ connected

Quick start

./run_demo.sh

Or manually, in three terminals (ports via env, defaults shown):

CHARLIE_PORT=5062 cargo run --bin charlie
BOB_PORT=5061 CHARLIE_PORT=5062 cargo run --bin bob
ALICE_PORT=5060 BOB_PORT=5061 cargo run --bin alice

Expected output

  [ALICE] Connected to Bob!
  [ALICE] Got REFER to sip:charlie@127.0.0.1:5062
  [ALICE] ✅ Connected to Charlie!
  [BOB] ✅ REFER accepted
  [CHARLIE] ✅ Answered!

✅ DEMO SUCCESSFUL — Alice was transferred to Charlie

Configuration

Ports come from ALICE_PORT / BOB_PORT / CHARLIE_PORT (defaults 5060 / 5061 / 5062) so the three binaries can be placed independently.

Beta scope notes

• REFER + the NOTIFY progress lifecycle (RFC 3515 / RFC 4235) are interop-tested.
• The transferee-drives-completion pattern keeps the flow explicit; the transfer_blind_and_wait outcome distinguishes REFER acceptance from failure.

Troubleshooting

• Alice never gets the REFER — Bob must be answered first; run_demo.sh starts Charlie and Bob before Alice.
• Port conflicts — override the *_PORT env vars.

Next steps

• 06-attended-transfer — consult the target first.
• In-crate reference: stream_peer/05_blind_transfer.