mqtt-proxy

Accepts MQTT connections of one protocol version and exposes the client id as a variable.

Category Other protocolsAdd it to Stream routeEngine plugin mqtt-proxyPriority 1000

What it does

mqtt-proxy lets only the MQTT clients of one protocol version through a stream route. It reads the CONNECT a client sends first and compares the protocol it names with Protocol name, MQTT unless you change it, and the level it names with Protocol level.

A client whose CONNECT matches reaches the broker, and the broker's answer comes back on the same connection. A client whose CONNECT names another level is cut off without a byte.

When to use it

• Sensors that connect with protocol level 4 on 1883 to a pool of brokers, while a client of any other level should be cut off at the gateway.
• A broker cluster that serves MQTT 5 alone, behind a port that turns older clients away with level 5.
• Old devices that still name the protocol MQIsdp, kept on a port of their own with level 3.

Not for capping how many connections a device keeps open — see limit-conn (Limits concurrent connections per key) or forwarding connections whatever protocol they speak — see Stream route (Stream routes forward raw TCP and UDP connections to an upstream).

Set it up

Pass connections of clients that speak MQTT protocol level 4 to the broker

A client whose CONNECT names another protocol level is cut off without a byte.

Leave Protocol name at MQTT and set Protocol level to 4.

mqtt-proxy · as the console saves it

{
  "protocol_name": "MQTT",
  "protocol_level": 4
}

Things to know

• Protocol level — With level 4 on a stream route whose server port is 9100, a CONNECT that names level 4 reaches the broker and its answer comes back, 20020000 in hex. A CONNECT that names level 5 is closed.
• Protocol name — A client whose CONNECT names another protocol is closed without a byte; MQTT 3.1 clients name MQIsdp, every later version MQTT.
• Protocol level — A client whose CONNECT names another level is closed without a byte: MQTT 3.1.1 clients send 4, MQTT 5 clients 5, MQTT 3.1 clients 3.
• Protocol level — A level is required; a plugin without one is refused when you save.
• Protocol level — The level is a whole number: 4.5 is refused when you save.
• The plugin also takes the client id from the CONNECT and makes it available as a variable.
• AdviceGive each MQTT version a port of its own, and put behind each port the brokers that serve that version.

Settings

The fields as the console shows them, section by section.

Protocol nameprotocol_namestringdefault MQTT

Protocol levelprotocol_levelintegerRequired

Every plugin also has Enabled, Priority, Filter, Error response and Pre-function: see Plugin execution settings.