PR Checklist

If you have any questions, you can refer to the Contributing Guide

What is the current behavior?

Currently, the MQTTX command-line tool does not allow customization of WebSocket headers when using WebSocket connections.

Issue Number

Example: #1722

What is the new behavior?

Added the ability to customize WebSocket headers through the -wh parameter in the command line. For example:

mqttx sub -t test -wh "hello: test" -wh "auth: token" -l ws -p 8083

Does this PR introduce a breaking change?

• Yes
• No

Specific Instructions

When reviewing this PR, please note the following:

1. This feature is implemented only in the command-line tool running in a Node.js environment.
2. Test scenarios with multiple -wh parameters to ensure multiple headers are correctly added.
3. Verify that the parameter is properly ignored for non-WebSocket connections.

Other information

This feature comes from user requests, allowing users to customize headers when using WebSocket connections, increasing connection flexibility. For example, users can add authentication information or other custom data.

It's important to note that this feature is only supported in the command-line tool running in a Node.js environment. Due to browser security restrictions, the Desktop and Web versions of MQTTX cannot modify WebSocket headers, and therefore cannot implement this feature. This is a known limitation, and detailed information can be found in the related discussion in the MQTT.js project: mqttjs/MQTT.js#856

This new feature will provide more connection options for command-line users, especially useful in WebSocket connection scenarios that require special authentication or custom headers.