Overview

Mon, 01 Jan 0001 00:00:00 +0000

What it is

The Ulai SIP Gateway is a single Go binary (sip-sfu-gateway) that joins two worlds:

SIP/RTP — a carrier trunk, speaking SIP over UDP, TCP or TLS, carrying G.711 audio over RTP or SRTP.
Ulai SFU rooms — WebRTC sessions on the Ulai control plane, where browsers and AI agents meet.

A phone call that reaches the gateway becomes an ordinary participant in a room. Everything the gateway does is in service of that one sentence: decide whether the call is allowed, get a room for it, answer it, and move audio in both directions until somebody hangs up.

Configuration

Mon, 01 Jan 0001 00:00:00 +0000

Configuration is read from the environment once, at startup, into a single validated struct. Everything downstream reads that struct, never the environment — which is also why a test can construct one directly.

Validation reports every problem at once, so a misconfigured deployment does not have to be fixed one restart at a time.

Required

Variable	Description
`ULAI_CONTROL_PLANE_URL`	Base URL of the Ulai control plane, e.g. `https://stgcp.ulai.co.in`. Rooms are created, joined and terminated here.
`SIP_ROUTING_REDIS_URL`	The routing store every call is resolved against. `REDIS_URL` is accepted as a fallback.
`SIP_PUBLIC_IP`	The address advertised in SDP and `Contact`. Must be routable by the carrier. `0.0.0.0` is rejected — it is not a listen address, it is what the carrier is told to stream media to.

SIP signalling

Variable	Default	Description
`SIP_LISTEN_ADDR`	`0.0.0.0:5060`	What sipgo binds to. `host:port`; the host may be `0.0.0.0`.
`SIP_TRANSPORT`	`udp`	`udp`, `tcp` or `tls`.
`SIP_TLS_CERT_PATH`	—	Required when `SIP_TRANSPORT=tls`.
`SIP_TLS_KEY_PATH`	—	Required when `SIP_TRANSPORT=tls`.
`SIP_SESSION_HEADER`	`X-Session-Id`	The INVITE header that may point a call at an existing room. Must not be blank.

RTP media

Variable	Default	Description
`SIP_RTP_HOST`	`0.0.0.0`	What RTP sockets bind to, as distinct from `SIP_PUBLIC_IP`, which is what is advertised. On most cloud VMs the public IP is attached at a NAT or load-balancer layer and is not on any interface inside the VM, so binding to it fails with cannot assign requested address. The default is right nearly everywhere.
`SIP_RTP_PORT_LOW`	`10000`	Bottom of the RTP allocation range.
`SIP_RTP_PORT_HIGH`	`10500`	Top of the range. Must be above the low end, and both within 1–65535. Even ports only, by RTCP convention.
`SIP_RTP_TIMEOUT_SECONDS`	`30`	End a call whose inbound audio has stopped for this long, as if the far end had hung up — the backstop for a `BYE` that never arrives. Paused while the call is on hold. `0` disables it.

HTTP API

Variable	Default	Description
`SIP_HTTP_PORT`	`8082`	Port for `/health`, `/calls` and `/sip/originate`. Chosen clear of the worker (8080) and the Tata gateway (8081).

Rooms

Variable	Default	Description
`ULAI_PROJECT_ID`	—	Default project for `POST /sip/originate` when the body omits `project_id`. The single-tenant deployment’s answer to sending it every time.
`ULAI_MAX_PARTICIPANTS`	`8`	Size of a room the gateway creates. Overridden per request by `max_participants`. Must be positive.
`SIP_TERMINATE_SESSION_ON_HANGUP`	`true`	End the whole session — every participant, every transport — when the SIP leg drops, rather than merely leaving the room. Set `false` only when a room reached via `X-Session-Id` or `session_id` is genuinely shared. A room the gateway created is always terminated regardless.

ICE

The gateway is STUN-only by default (stun:stun.l.google.com:19302), which is fine on a public host and will fail behind symmetric NAT.

HTTP API

Mon, 01 Jan 0001 00:00:00 +0000

Three endpoints, served on SIP_HTTP_PORT (default 8082). Only /sip/originate is authenticated.

Method	Path	Auth
`GET`	`/health`	none
`GET`	`/calls`	none
`POST`	`/sip/originate`	`Authorization: Bearer <ulai api key>`

These endpoints are not public

/health and /calls are unauthenticated, and /calls lists live phone numbers. Keep the HTTP port on a private network or behind a firewall; only /sip/originate checks a credential.

GET /health

curl -s http://148.113.58.51:8082/health

{ "status": "ok", "service": "sip-sfu-gateway" }

Always 200 while the process is serving. It says nothing about the SIP leg or the routing store — see observability for a check that covers both.

SIP Gateway on Ulai Docs

Overview

What it is

Configuration

Required

SIP signalling

RTP media

HTTP API

Rooms

ICE

HTTP API

GET /health