Failed to establish a connection with TLS/MQTTS broker using mqttclient

I am attempting to make an application utilizing OpenF1's MQTT stream but am having issues creating a connection. The following information is provided by the documentation:

Connection Details

• MQTT server: mqtt.openf1.org
• MQTT port (TLS/MQTTS): 8883
• Websockets URL (WSS for MQTT over Websockets): wss://mqtt.openf1.org:8084/mqtt

Authentication

Both MQTT and Websocket connections use the OAuth2 access token as the password for authentication. The username can typically be any non-empty string, or your registered email if preferred/required by your client library for token-based auth.

after receiving a token I am able to establish a connection on MQTTX with settings:

Host: mqtts:// mqtt.openf1.org

SSL/TLS : Yes

SSL Secure: No

Certificate: CA signed server certificate

However in MATLAB, all variations of the following line are met with error message "Failed to establish a connection with broker"

mqttClient = mqttclient("ssl://mqtt.openf1.org", Username="[e-mail]", Password=token, Port=8883, CARootCertificate="mqtt.openf1.org.crt")

The certificate was downloaded via the method described in https://www.mathworks.com/matlabcentral/answers/1889632-how-to-download-root-certificate-for-use-with-industrial-communication-toolbox-mqtt-functions.This is my first time using MQTT, please help me identify my error or suggest troubleshooting steps.

Answer 1

[Kautuk Raj]

I was also seeing the same error in one of my workflows when trying to connect to a secure MQTT broker from MATLAB.

I found a discussion on a GitHub issue (https://github.com/eclipse-paho/paho.mqtt.c/issues/1385) which helped me resolve the issue, I will reproduce it below for your convenience.

You can resolve the issue by specifying the path after the port number in the URL in the following format:

protocol://hostname:port/path

instead of using protocol://hostname/path:port

Answer 2

[Govind KM]

Hi @Spencer Carlyle,

I was facing a similar error message when trying to connect an MQTT client over websockets in MATLAB R2024b, but was able to connect successfully in R2025a. If possible, I would recommend upgrading to the R2025a release and trying out the same workflow.