I’ve been working on establishing an MQTT connection from my Siemens LOGO! PLC (using LOGO! Soft Comfort v8.4) to a registered Zoho IoT device that includes proper credentials (username, password, and TLS settings). However, I consistently encounter a “Failed to parse” error when attempting to connect to Zoho’s MQTT broker.

Interestingly, when I configure the same setup to connect to a local Mosquitto MQTT broker, the connection is successful. This confirms that the basic MQTT configuration on the PLC side is functional.

Given this, I'm unsure what's blocking the connection specifically to Zoho’s broker. Could it be due to:

• Incompatibility in MQTT protocol versions?
• A TLS handshake or CA certificate mismatch?
• Authentication method differences?
• DNS or hostname resolution issues in LOGO?
• Or, do I need to implement an MQTT bridge using a tool like Node-RED to act as an intermediary between the LOGO PLC and Zoho?

Any guidance or suggestions to help troubleshoot or work around this issue would be appreciated.

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Split from Logo Software and Harware.

Topic closed because the question has been posted twice. The active topic can be found here:

Issue Connecting Siemens LOGO! PLC to Zoho IoT via MQTT (Soft Comfort v8.4)

Kind regards, Moderator_Lan