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MQTT - Unity interface

[!WARNING] This documentation is set to be partialy merged with the API documentation for Unity.

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Project owner: Yann van Eijk
Unity version 2021.3.27f1

Project description

This repository contains the scripts needed within Unity to create an interface between MQTT and Unity. Its main functionality is to receive and sent real-time messages from topics on the MQTT Broker. These messages are processed within Unity as strings, for other types use TryParse.

Installation

The MQTT package is part of the 'DT lab Unity interface package'. For a full installation guide, please refer to...

MQTT broker connections

Establishing a connection to the MQTT broker is facilitated through the MQTT editor window, accessible via Tools -> EAISI Digital Twin Lab -> MQTT editor. Upon opening, a new window will appear next to the Inspector window.

To configure the connection, the following parameters must be configured:

Variable Type Description Optional/ Required
Server adress String Hostname or IP adress of MQTT Broker. Required
Port String Port number of MQTT on broker. Required
Use Credentials Boolean Some MQTT brokers require user credentials for connections. If this is the case for the broker you want to connect to, tick this box. Optional (Check broker)
Use Encryption Boolean Some MQTT brokers require an encrypted connection. If this is the case for the broker you want to connect to, tick this box. Optional (Check broker)
Username String Username of account set at MQTT broker. Optional (see Use Credentials)
Password String Password of account set at MQTT broker. Optional (see Use Credentials)
Topics List<String> List of topics to subscribe to. All subscription topics used in the Unity project should be declared here. Optional (Required for subscription functionality)
Connect to MQTT broker at runtime Boolean Disables editor time connection and enables connection upon entering runtime. Only enable this setting after testing the connection in editor time. Optional

Upon opening the editor window initially, the Server Address and Port variables are pre-configured. This allows quick testing of a connection to test.mosquitto.org. To verify, click the gray connect button at the bottom of the MQTT editor window. A debugging message should appear in the console stating Connected to: test.mosquitto.org:1883, indicating successful functionality.

Workflow

  1. Setup MQTT broker. If you already have an account and password provided by the Digital Twin Lab or if you already setup your own broker, go to step 2. For certain projects it is possible to make use of the MQTT broker of the Digital Twin Lab. If you want to make use of the MQTT broker of the Digital Twin Lab, but dont have credentials yet, please contact us via e-mail.
  2. Open the MQTT Editor Window via Tools -> EAISI Digital Twin Lab -> MQTT editor in the Unity Editor. A new window will open alongside the Inspector window.
  3. To test the library, click the Connect button on the bottom of the MQTT editor window without altering any parameters. This solely tests if the interface can connect to an MQTT broker; no messages are relayed. A message stating Connected to: test.mosquitto.org:1883 should pop up in the Console window within Unity. Clicking Disconnect disconnects the Unity client from the MQTT broker, indicated but the message Disconnected from: test.mosquitto.org:1883.
  4. Establish the connection to the desired MQTT broker. Ensure to complete step 1 of this workflow.
  5. Fill in the parameters in the MQTT editor window as described in MQTT broker connections based on your MQTT broker settings. Click Connect, if no connection is established, an error message will pop up in the Console. I.e. SocketException: Could not resolve host 'test.mosquittofalse.org', indicating the wrong server adress. Any error concerning a MqttCommunicationTimedOutException indicates a wrong port. If a connections is established, click Disconnect.
  6. If applicable, test receiving messages from the MQTT broker by adding subscription topics in the Topics list. Click the + button and enter the full path to the variable intended for reception in Unity. After clicking Connect, the topic and value should display in the Received header at the bottom of the MQTT editor. Click Disconnect.
  7. If applicable, test sending messages to the MQTT broker from Unity. After clicking Connect, a Publish header should appear below the Disconnect button. Enter the topic's path in the Topic field and the message to publish in the Message field. To verify message reception, check the MQTT broker or any MQTT client subscribed to the publishing topic. Click Disconnect.
  8. To receive messages at runtime, populate all topics intended for subscription dor the Unity project in the Topics section and check the Connect to MQTT broker upon entering runtime box. Once checked, no changes can be made to the MQTT editor window. Unity will automatically connect to the MQTT broker and subscribe to the specified topics. To access received messages at runtime, utilize something like the DataManager script attached to the Data Object prefab found under the folder .../DT lab/MQTT. This script subscribes to all topics listed in the subscription topic list of the editor window via the MessageManager. It stores these values in a public string each time the value changes and uses the Update() functionality to display them in the Inspector window. In summary, to receive data from a topic at runtime, your MonoBehaviour script should call: 
    
 MessageManager.Instance.SubscribeToTopic(topic, HandleFunction);
    Where topic is the subscription topic, and HandleFunction is the function that gets called when the value on the topic gets updated. An example of this is shown below. 
    
 private void HandleFunction(string topic, string message)
 {
     SubscribedTopics[topic] = message;
 }
    This function stores the received message of the topic in the dictionary SubscribedTopics, though self-defined function can be used as well.
  9. Publishing in run time can be achieved by calling the function below. 
    
 MQTT_lib.PublishToTopic(TopicToPublish, message.ToString());
    TopicToPublish is a string of the full path of the topic you want to pulbisch to. message is the message to publish. Make sure this message is converted to either a string or JSON format.
  10. Steps 6 to 9 can be iterated as needed to attain the desired data interface between Unity and the MQTT broker.

Development

  1. Code needs to be reviewed.
  2. Build needs to be checked.
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