Component: MQTT Client (Comms: IoT/Cloud)

Author	Matrix TSL
Version	1.1
Category	Comms: IoT/Cloud

MQTT Client component

A component providing access to MQTT IoT client. The client can connect to a MQTT server such as ThingSpeak. Allowing IoT type data to be published and read back.

Version information

Library Version, Component Version, Date, Author, Info
7, 1.1, 23-07-24, BR, Added Max Packet Size property to allow the size of a single packet to be altered by the user
8, 1.1, 30-07-24, BR, Resolved ESP compile error due to missing return and added TopicTooLong error

Detailed description

No detailed description exists yet for this component

Examples

The MQTT component requires connection to a Network Comms component via the "Network Component" property, to provide the bridge for simulated TCP/IP communication.

The Network Comms component can then be linked to an embedded TCP/IP component to provide embedded TCP/IP support.

Here is a typical setup for using MQTT on a Raspberry Pi.

Local Weather

A simple example demonstrating how to use MQTT with Flowcode SCADA to get the local weather conditions.

The example shows temperatures from Halifax in the UK and from Sydney in Australia.

SCADA BBC TEMPERATURES

Publish

Raspberry Pi

Here we have an embedded Raspberry Pi project connected to an I2C Sensor, the sensor is sampled and the data is published to a MQTT server.

RPI3 MQTT IOT EBM016

ESP8266 Module

Here we have an embedded project using an ESP8266 wifi module, an analogue input is sampled and the data is published to a MQTT server.

MQTT IOT ESP8266

Subscribe

ESP8266 Module

Here we subscribe to a topic and receive it back into Flowcode embedded using an ESP8266 module.

Subscribe ESP8266 MQTT

Flowcode App Developer

Here we subscribe to a topic and receive it back into Flowcode App Developer.

Subscribe App Developer MQTT

Making your own Raspberry Pi based MQTT Broker

Click here for instructions on creating your own Raspberry Pi MQTT Broker.

Macro reference

Connect

	Connect
Connect to the MQTT Server. Returns the connected state. 0 if not connected, 1 if successful connection, or already connected.
- BYTE	Return

ConnectTo

	ConnectTo
Connect to a variable MQTT Server, overriding the Host and Port properties. Returns the connected state. 0 if not connected, 1 if successful connection, or already connected.
- STRING	Host
- UINT	Port
- STRING	ClientID
Client identifier name - must be unique on server
- BYTE	Return

Disconnect

	Disconnect
Disconnects from the MQTT server and the network
- BYTE	Return

ErrorAsString

	ErrorAsString
- BYTE	Error
- STRING	Return

GetPayload

	GetPayload
Get the Payload of the last received (Read) packet. Returns the number of bytes for the Payload
- STRING	Payload
- BYTE	Size
Byte count the Payload buffer
- BYTE	Return

GetTopic

	GetTopic
Get the Topic of the last received (Read) packet. Returns the number of bytes for the Topic
- STRING	Topic
- BYTE	Size
Byte count the Topic buffer
- BYTE	Return

Initialise

	Initialise
- VOID	Return

LastError

	LastError
Returns the last error
- BYTE	Return

Ping

	Ping
Ping packet is sent to the Server and checks for a reply. Returns non-zero value if successful
- BYTE	Return

Publish

	Publish
Publish data to the server (broker) Returns non-zero if successful
- STRING	Topic
- STRING	Payload
- BYTE	Return

Read

	Read
Read incoming data. Returns non-zero if packet received. Use GetTopic and GetPayload to read the contents.
- UINT	Return

Subscribe

	Subscribe
Subscribe to a Topic. Must be Connected first Returns non-zero if successful
- STRING	Topic
- BYTE	Return

Unsubscribe

	Unsubscribe
Unsubscribe from a Topic. Must be Connected first Returns non-zero if successful
- STRING	Topic
- BYTE	Return

Property reference

	Properties
	LinkTo
	Host
Address of MQTT Broker Can be an IP Address or URL (URL only supported by some hardware platforms)
	Port
Port used by MQTT Broker Default 1883 for unencrypted access and 8883 for encrypted access.
	Client identifier
Client identifier (Maximum length 20 characters) Must be unique to the broker.
	Network Timeout
Maximum time in mS to wait for network responses
	Read Timeout
Amount of time in ms to wait for incoming messages.
	Keep Alive
The Keep Alive is the maximum time interval that is permitted to elapse between the point at which the Client finishes transmitting one Control Packet and the point it starts sending the next, measured in seconds.
	Authentication
Selects if the broker is open or if the broker requires a username and password.
	Max Packet Size
Sets the number of bytes that can be sent and received in a single packet. A single packet consists of 4 header bytes, plus the topic and payload string data.

Component Source Code

Please click here to download the component source project: FC_Comp_Source_MQTT_Client.fcfx

Please click here to view the component source code (Beta): FC_Comp_Source_MQTT_Client.fcfx