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MQTT Client (advanced)

An MQTT client for GDevelop: allow connections to a MQTT server and send/receive messages.

Authors and contributors to this community extension: arthuro555.

This extension wraps MQTT.js to allow connections to a MQTT server and communication via pub/sub. The only transport method is Websockets. Make sure to use a broker that support those!


The dataloss let you chose how to handle data. Due to how the GDevelop event loop is made, only one message per topic can be processed per frame. When dataloss is on, when you get 2 messages from one topic in one frame, only the latest one is remembered. When it is off, the first message is processed and the second is queued for the next frame.

QoS (Quality of service)

Here is how QoS works:

  • QoS 0 (received at most once): The packet is sent, and that's it. There is no validation about whether it has been received.
  • QoS 1 (received at least once): The packet is sent and stored as long as the client has not received a confirmation from the server. MQTT ensures that it will be received, but there can be duplicates.
  • QoS 2 (received exactly once): Same as QoS 1 but there is no duplicates.

About data consumption: QoS 2 will consume more than QoS 1, which will consume more than QoS 0.


Learn how to install new extensions by following a step-by-step guide.


Connect to a broker
Connects to an MQTT broker.

Disconnect from broker
Disconnects from the current MQTT broker.

Publish message
Publishes a message on a topic.

Subscribe to a topic
Subcribe to a topic. All messages published on that topic will be received.

Unsubscribe from a topic
Unsubcribe from a topic. No more messages from this topic will be received.


Is connected to a broker?
Triggers if the client is connected to an MQTT broker server.

On message
Triggers whenever a message was received. Note that you first need to subcribe to a topic in order to get messages from it.


Expression Description
MQTT::GetLastMessage(string) Get the last received message of a topic.
string The topic to get the message from
MQTT::getCurrentError() Gets the last error. Returns an empty string if there was no errors.

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