MQTT - v5 Generic

5 min

The MQTT - v5 Generic connector enables Litmus Edge (LE) to connect to an MQTT v5 broker. Set Connection Type to tcp for an unencrypted connection, or to ssl for a TLS-encrypted connection.

Supported versions

Compatible with MQTT protocol versions 3.1.0, 3.1.1, and 5.0.0.

Supported communication

Outbound (publish data from LE to the MQTT broker): Yes

Inbound (subscribe to data from the MQTT broker to LE): Yes

Configurations

Note: When you add an outbound topic for this connector, a Retain option is available. When enabled, the broker retains the last published message on that topic, so new subscribers receive it immediately when they connect. Inbound topics have No Local, Retain as Published, and Retain Handling options. See Add Topics to Connectors for details.

Variable	Detail	Required
Name	Connector name.	Yes
Connection Type	tcp for an unencrypted connection, or ssl for a TLS-encrypted connection. Default tcp.	Yes
Hostname	DNS name or IP address of the MQTT broker. The broker must be reachable from the LE system.	Yes
Port	MQTT broker port. Default 1883. The usual TLS port is 8883.	Yes
CA Certificate	CA certificate in PEM format, used to verify the broker. You can also install it in the system-wide certificate store. Shown only when Connection Type is ssl.	No
Certificate	PEM client certificate for mutual TLS authentication with the broker. Shown only when Connection Type is ssl.	No
Private key	Private key that matches the client certificate. Shown only when Connection Type is ssl.	No
Insecure Skip Verify	Skip verification of the broker's certificate chain and host name. Use only for testing. Default disabled. Shown only when Connection Type is ssl.	No
Client ID	Unique client identity. If you leave it empty, LE uses the connector's instance ID.	No
Username	User name.	No
Password	User password.	No
QoS	Quality of Service delivery guarantee: 0 = at most once, 1 = at least once, 2 = exactly once. Default 1. The QoS levels available can depend on the broker configuration.	No
Integration Topic	MQTT topic that data is published to. Supports dynamic topics.	Yes
User Properties	Custom key-value metadata attached to outgoing MQTT v5 packets. The broker passes it through to subscribers.	No
Parallel Publish Count	Number of messages published in parallel. Higher values increase throughput and resource usage. Range 1 to 4000. Default 100.	No
Response Topic	MQTT v5 topic that the receiver should publish its response to, for request-response messaging.	No
Payload Format Indicator	Format of the payload in CONNECT and PUBLISH packets: utf-8 or byte. Lets the server understand the packet without reading the payload. Default utf-8.	No
Content type	MIME type that describes the payload format, such as application/json. Passed to subscribers for information.	No
Topic Alias Maximum	Maximum number of topic aliases. Topic aliases reduce packet overhead by replacing the topic name with a small integer. Range 1 to 7. Default 7.	No
LWT topic	MQTT topic the broker publishes the Last Will message to if this client disconnects unexpectedly.	No
LWT payload	Message content published to the LWT topic on unexpected disconnection. Maximum 255 characters.	No
LWT payload type	Encoding of the LWT payload: string for plain text, base64 for binary data. Default string.	No
LWT QoS	QoS level for the Last Will message: 0, 1, or 2. Default 1.	No
LWT retained	If enabled, the broker retains the Last Will message and delivers it immediately to any new subscriber on that topic. Default disabled.	No
Will Delay Interval	Delay in seconds between the end of the connection and sending the Last Will message. Range 0 to 60. Default 0.	No
Session Expiry Interval (seconds)	How long the broker keeps the client's session information. Range 0 to 60. Default 0.	No
Message Expiry Interval	Expiry interval, in seconds, set on each published message. Default 0.	No
Request Response Info	Ask the broker to return response information, such as a response topic prefix, in the CONNACK packet. Default disabled.	No
Request Problem Info	Ask the broker to include reason strings and user properties in error packets, such as PUBACK and SUBACK. Default disabled.	No
Keep Alive	Keep-alive duration in seconds. The connector sends a packet at least this often, so the connection stays active even when no data is sent. Under MQTT 5.0, if the broker receives nothing within 1.5 times this duration, it closes the connection. Range 1 to 60. Default 60.	No
Connection Timeout	How long to wait for the connection to complete, in seconds. Range 1 to 60. Default 10.	No
Throttling limit	Maximum outbound messages per second. If the broker limits the rate of incoming messages, this ensures that no messages are lost. A value of 0 disables throttling. Default 0.	No
Persistent storage	If enabled, messages in the outbound queue are stored on disk. If there are interruptions in connection or power loss, messages are retained and sent when the connection is restored. Default enabled.	No
Queue Mode	Order in which buffered messages are sent: fifo (First In First Out) sends the earliest message first, and lifo (Last In First Out) sends the latest message first. Default lifo. Shown only when Persistent storage is enabled.	No
Persistent storage size limit	Size limit for persisted data, in GB. Default 1. Shown only when Persistent storage is enabled.	No
Enable Logging	Write connection and publish error messages to the connector log. Logging can increase CPU usage, so enable it only for debugging. Default disabled.	No

Format directives

Symbol	Definition	Context
$	A variable follows. A variable represents a dynamic string value. The supported variables are:	-
$S	Additional Alias definition	from connector settings
$D	Device Name	from DeviceHub tag
$N	Tag Name	from DeviceHub tag
$R	Raw Tag Type	from DeviceHub tag
$P	Tag Description	from DeviceHub tag
$H	Hostname	from OS
%	A function follows. A function acts on the next variable. The supported functions are:	-
%L	Lowercase()	apply to next variable
%U	Uppercase()	apply to next variable

Format directives notes

To use a special character literally, enter it twice: $$ for $, and %% for %.

Example: "$$$D.%%$N" becomes "$deviceABC.%tagXYZ".

Compatibility validation

This information is for reference only. More products and versions may be supported, provided they are compatible with the supported versions listed above.