WebSockets

LavinMQ supports both AMQP and MQTT over WebSocket connections, enabling browser-based clients and traversal of firewalls that block non-HTTP traffic.

Endpoints

Path	Protocol
/mqtt	MQTT over WebSocket
/ws/mqtt	MQTT over WebSocket
any other path	AMQP over WebSocket

WebSocket upgrade requests are accepted on the management HTTP port. Protocol selection follows this order:

1. If the Sec-WebSocket-Protocol header is set, the protocol is selected from it:
   • amqp (or any token starting with amqp, case-insensitive) — AMQP 0-9-1
   • mqtt (or any token starting with mqtt, case-insensitive) — MQTT
2. Otherwise, the path is used: /mqtt and /ws/mqtt route to MQTT; any other path routes to AMQP.

Conventionally, clients use /ws for AMQP, but the path itself is not significant when the sub-protocol header is set.

Port

WebSocket connections use the same HTTP port as the management UI and API:

Config Key	Default
port in [mgmt]	15672
tls_port in [mgmt]	15671 (WSS)

How It Works

WebSocket connections are proxied to the internal AMQP or MQTT server. The WebSocket handler:

1. Upgrades the HTTP connection to a WebSocket
2. Detects the protocol from the sub-protocol header or URL path
3. Creates a bidirectional IO bridge between the WebSocket and the protocol handler

From the protocol handler's perspective, the connection behaves identically to a direct TCP connection.

Client IP

The client's remote IP address is taken from the HTTP request's TCP connection.