{"id":28,"date":"2023-06-01T14:48:22","date_gmt":"2023-06-01T18:48:22","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/iotplatform\/?post_type=chapter&p=28"},"modified":"2023-09-22T12:06:47","modified_gmt":"2023-09-22T16:06:47","slug":"chapter-3","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/iotplatform\/chapter\/chapter-3\/","title":{"raw":"Connecting a Virtual Client to TB","rendered":"Connecting a Virtual Client to TB"},"content":{"raw":" \r\n

In TB, the registered device serves as the connection point between the telemetry data and the platform, utilizing the MQTT (Message Queue Telemetry Transport) protocol. However, TB also supports other communication protocols such as NB-IoT, Sigfox, and LoRa [footnote]https:\/\/thingsboard.io\/docs\/samples\/[\/footnote]<\/span><\/span>. A detailed description of these protocols is beyond the scope of this chapter.<\/p>\r\n

As mentioned in the previous chapter, displaying telemetry data on the dashboard involves four basic steps: 1) adding the device, 2) adding the dashboard, 3) adding the alias, and 4) adding the widget. Once these settings are configured, TB is ready to establish communication with the device to receive the telemetry data. In this chapter, we will explore how to use Python programming to publish data to TB. Before delving into the Python code, let's take a brief overview of the MQTT protocol.<\/p>\r\n\r\n

3.1\u00a0 MQTT Protocol<\/span><\/strong><\/h1>\r\n

The MQTT protocol is widely used messaging protocol in the Internet of Things (IoT) domain. It defines a set of rules that govern the exchange of data between IoT devices over the Internet. MQTT is commonly used for both consumer and industrial IoT (IIoT) applications. The protocol follows an event-based communication model, employing the concepts of publishers and subscribers to establish a Pub\/Sub (Publish\/Subscribe) pattern for device connectivity [footnote]https:\/\/thingsboard.io\/docs\/samples\/[\/footnote] <\/span><\/span>[footnote]https:\/\/thingsboard.io\/docs\/samples\/esp8266\/[\/footnote] [footnote]https:\/\/thingsboard.io\/docs\/user-guide\/integrations\/send-data-external-mqtt-brokers\/[\/footnote] .<\/span><\/span><\/p>\r\n

Publishing refers to the process where a device sends data to a server, also known as a broker. On the other hand, subscription refers to the process of receiving data from the broker. MQTT client libraries can be found on the Internet, catering to various types of publishers and subscribers. data is differentiated from one another using \"topics\", which serve as identifiers within the MQTT ecosystem. The broker acts as an intermediary, managing the communication between IoT devices. It functions as a server, while the connected devices operate as clients. The MQTT broker ensures that they are delivered correctly to the subscribed clients.<\/p>\r\n\r\n

1.\u00a0\u00a0\u00a0 MQTT Client<\/strong><\/span><\/h2>\r\n

In the MQTT protocol, both publishers and subscribers are referred to as clients. The distinction between a publisher and a subscriber lies in their respective roles in the message exchange process. Publishers are clients that send messages or data to the broker server, while subscribers are clients that have subscribed to the broker server to receive messages.<\/p>\r\n

The MQTT client can encompass a wide range of devices, from small microcontrollers to large servers capable of handling the TCP\/IP stack required for network communication with the MQTT server. For instance, an MQTT client could be a resource-constrained device connected via a wireless network, running minimal code. Since MQTT is built on top of TCP\/IP, both the client and the broker must support this network stack.<\/p>\r\n

Implementing the MQTT protocol in a client is relatively straightforward and efficient compared to other protocols like HTTP, requiring minimal resources. Therefore, MQTT is particularly suitable for IoT solutions with limited resources. Numerous programming languages, such as Python, Java, JavaScript, and C\/C++, have developed libraries to support MQTT. The MQTT wiki [footnote]https:\/\/thingsboard.io\/docs\/iot-gateway\/config\/mqtt\/[\/footnote]<\/span><\/span> provides a comprehensive list of these libraries, enabling developers to leverage MQTT in their preferred programming languages.<\/p>\r\n\r\n

2.\u00a0\u00a0\u00a0 MQTT Broker<\/strong><\/span><\/h2>\r\n

In the MQTT protocol, the broker plays a central role in facilitating publish\/subscribe communication. A single broker has the capability to handle a large number of connected MQTT clients simultaneously. In the MQTT architecture, clients do not directly communicate with each other but instead communicate through the broker. The broker performs several essential functions, including:<\/p>\r\n\r\n