Using MQTT.fx to connect to EMQ X Cloud

This article will take MQTT.fx as MQTT client test tool to connect to MQTT Cloud Service - EMQ X Cloud. Through this article, you will be able to quickly understand the basic usage of MQTT.fx and the basic concepts and usage of the MQTT protocol.

Introduction to MQTT.fx

MQTT.fx is the most popular MQTT desktop client tool currently. The major version of MQTT.fx 1.0 is developed by Jens Deters using JavaFX technology, which is a Java virtual machine application. Unfortunately, the maintenance of MQTT.fx has now stopped maintenance and Softblade company has sponsored the development and released its commercial version MQTT.fx® 5.0, which is operated with a fee-based license. MQTT.fx in this article refers to version 1.0 without special instructions.

It contains mainstream MQTT client functions:

• Basic subscribe/publish/connect function
• User Authentication
• SSL/TLS connection support
• Easy to use message editing bar
• Support agent

In addition, MQTT.fx also has other excellent features:

• The software is free, and its open source protocol is Apache 2.0 license
• Support cross-platform
• Support $SYS topic subscription management MQTT Broker
• Complete log console
• Support JavaScript to process messages
• Support predefined templates

But there are also defects:

• MQTT 5.0 protocol is not supported
• Only one connection can be established at a time, which is inconvenient for multi-connection debugging
• WebSocket protocol is not supported and the situation of MQTT over Webscoket cannot be debugged

Introduction to EMQ X Cloud

EMQ X Cloud is a fully managed cloud-native MQTT service launched by EMQ company that can connect to a large number of IoT devices and integrate various databases and business systems. As the world's first fully managed MQTT 5.0 public cloud service, EMQ X Cloud provides MQTT message service with one-stop operation and maintenance management and a unique isolation environment.

In the era of the Internet of Everything, EMQ X Cloud can help users quickly build industry applications for the IoT area and easily realize the collection, transmission, calculation, and persistence of IoT data.

This article will use Free Public MQTT Server provided by EMQ X Cloud as the MQTT server address for this test. The server access information is as follows:

• Broker: broker.emqx.io
• TCP Port: 1883
• SSL/TLS Port: 8883

For more details, please visit EMQ X Cloud website or check EMQ X Cloud documentation.

MQTT.fx usage

Preview

The main page is shown in the figure below. The top part is the MQTT Broker connection address bar and its connection configuration. The following function Tabs include Publish column, Subscribe column, Scripts column, Broker Status column, Log column for log information control.

Each tab supports dragging into a separate window, as shown in the following figure:

Connect

First, the MQTT client and Broker need to establish a connection to communicate. Click the configuration icon on the right side of the input box in the connection address bar to enter the specific connection configuration.

Select the Profile Type as MQTT Broker. Fill in broker.emqx.io for Broker Address and 1883 for Broker Port, as shown in the figure below:

Click OK to confirm the configuration, return to the main interface, and click Connect. It can be seen that the circle on the right turns to green, indicating that the current connection is successful, as shown in the following figure:

Subscribe/Publish messages

Once the connection is established, you can start subscribing to messages. Because the MQTT protocol adopts the subscribe/publish method, we need to subscribe to the topic after connecting. After a message is generated on the topic, we can receive the messages from EMQ X cloud.

Click to enter the Subscribe Tab to enter /testTopic/1 in the topic box. Then, click the Subscribe button, and the list of subscribed topics will appear on the left. The current number of subscribed topics is 0, as shown in the following figure:

After that, we will publish the message to the broker. Return to Publish, enter the topic /testTopic/1, and enter the message of "hello world" in the message input box, as shown in the following figure:

Click Publish to send the messages and return to the Subscribe Tab. We can find that the subscribed topic /testTopic/1 has received the message, as shown in the following figure:

We use the client MQTT.fx to send the message "hello world" to the topic /testTopic/1 under EMQ X Cloud. All clients that have subscribed to this topic will receive this message, including the sending clients who have just subscribed to this topic.

Script

You can customize the message publish logic more flexibly by using the script. Click Script Tab and Edit to modify the script content as follows:

function execute(action) {
    mqttManager.publish("/testTopic/1", "hello world from script");
    return action;
}

Among them, mqttManager is the API to open the MQTT.fx script function, mainly including the following:

• publish()，publish messages
• subscribe()，subscribe to topics
• unsubscribe()，unsubscribe to topics
• output，output messages to the console

Click Execute, return to Subscribe column and find that the message is added with the content of "hello world from script". The script sending function is normal, as shown in the figure below:

Log

In the log, we can view the interaction process between MQTT.fx and EMQ X Cloud, such as topic subscription, message publish, message reception, etc.:

SSL/TLS connection

We take CA self-signed service as an example to show how to enable SSL protocol to connect to EMQ X Cloud.

Open the settings, fill in the Broker Address and Broker Port (broker.emqx.io and 8883 respectively) like normal connections, select the SSL/TLS item, select the TLSv1.2 protocol, check CA signed server certificate , and then select the application, as shown in the figure below:

Click Connect, and you can see that the lock icon on the right is closed, indicating that SSL is enabled. Check the log, and you will find the words related to SSL connection port 8883. The connection to SSL/TLS is successful.

The above is a simple example of using MQTT.fx to access EMQ X Cloud. For more details, please visit EMQ X Cloud.