Monitoring via MQTT

RUT monitoring via MQTT Linux guide

Summary

MQTT (MQ Telemetry Transport or Message Queue Telemetry Transport) is an ISO standard (ISO/IEC PRF 20922) publish-subscribe-based messaging protocol. It works on top of the TCP/IP protocol. It is designed for connections with remote locations where a "small code footprint" is required or the network bandwidth is limited. The publish-subscribe messaging pattern requires a message broker. This chapter is a guide on how to configure a basic MQTT setup on RUT routers.

How MQTT works

First lets look over how MQTT works on RUT routers. An MQTT connection takes place between two Clients and a Broker. A RUT router can be Broker, a Client or both. The MQTT Publisher (Client) present in RUT routers subscribes to two topics by default: router/get and get/<SERIAL>/command, where <SERIAL> is the router's serial number. When a third party client connects to the Broker, it sends the message id to the the topic router/get. The publisher then sends a response containing its serial number to the topic router/id. Now that the Client knows the router's serial number it can ask for values of various parameters by sending requests to the topic router/<SERIAL>/parameter_name. The MQTT Publisher can send responses containing values of these system parameters:

Parameter name	Parameter description
temperature	Temperature of the module in 0.1 degrees Celsius
operator	Current operator’s name
signal	Signal strength in dBm
network	Current network type (2G, 3G, 4G)
connection	Data connection status
wan	WAN IP address
uptime	System uptime in seconds
name	Router’s name
digital1	Value of digital input no. 1
digital2	Value of digital input no. 2
analog	Value of analog

After the client sends a message containing of these parameters, the Publisher will send a response message containing the value of the requested parameter to the topic router/<SERIAL>/parameter_name, where parameter_name is the name of the requested parameter.

It should also be noted that, according to the MQTT protocol, topic names are case-sensitive, for example topic router is not the same as topic RoUtEr.

Configuring the router

This section will provide an explanation on how to configure an MQTT Broker and MQTT Publisher on a RUT router.

Broker

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Basic (not counting Security, Bridge and Miscellaneous Broker settings) Broker configuration only contains three fields. Make sure to Enable the Broker and specify a Port for connection to the Broker. Enable Remote Access if you wish to connect to your router remotely (via WAN). Although in this case your router would need to have a Public IP address.

Publisher

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Publisher configuration is similar in its simplicity to the Broker configuration. Make sure to Enable the Publisher and specify a Port for connection to a Broker. If you plan on using the router's Broker, specify the same port as the one in the Broker Settings section. Hostname is the Broker's host name or IP address. If you're using the router's Broker, specify your router's LAN IP address. Username and Password are optional and depend on the type of security (if any) that the Broker uses.

Downloading Mosquitto

Once the Broker is up, you'll need install Mosquitto and Mosquitto Clients. To do so, open the Linux Terminal app and enter this command:

$ sudo apt-get install mosquitto mosquitto-clients

Now you can use set up Brokers and Clients on your PC. Continuing from the example above, lets say we want to monitor the router's signal strength and up time values. In order to do that we'll need to subscribe to the topics router/<SERIAL>/signal and router/<SERIAL>/uptime using the mosquitto_sub command. Open a second Terminal window and enter this command:

$ mosquitto_sub -h 192.168.1.1 -p 1833 -u user -P pass -t router/<SERIAL>/signal -t router/<SERIAL>/uptime

-h indicates the host (the Broker's IP address) which, continuing from the example above, is 192.168.1.1. Replace this value with your router's LAN IP address or, if you're using MQTT remotely, your WAN IP address.

-p indicates the port used for connection to the Broker. Replace it with the port number that you specified in the Broker configuration.

-u and -P specify the username and password. If the Broker doesn't require authentication, these values aren't mandatory. Else replace them with the log in information of your Broker.

Lastly, -t specifies the topics that you want to subscribe to, in this case it router/<SERIAL>/signal router/<SERIAL>/uptime. Replace <SERIAL> with your router's serial number. You can find your router's serial number in the Status → Device section of the router's WebUI. Or you can first subscribe to the topic router/id and publish the message id to the topic router/get. The full command would look like this:

$ mosquitto_sub -h 192.168.1.1 -p 1833 -u user -P pass -t router/id

To publish a message asking the router for it's serial number, or id, use this command:

$ mosquitto_pub -h 192.168.1.1 -p 1833 -u user -P pass -t router/get -m id

The mosquitto_pub command is used to publish messages to specified topics. -m defines the message that you're publishing. Again, replace the values given with the ones in your configuration. The whole exchange is presented in the picture below:

File:Configuration examples mqtt router id.png