Can’t Connect to AWS IoT Core via MQTT in Postman (port 8883, TLS certs)
Hi everyone, I’m currently working on a project using AWS IoT Core, and I want to test MQTT messages using Postman’s new MQTT client. I’ve followed the AWS IoT setup: Created a thing Attached policy Downloaded certificate, private key, and root CA I’m using the following config in Postman: Host: ........-ats.iot.ap-southeast-1.amazonaws.com Port: 8883 Protocol: mqtts Client cert and key: uploaded correctly CA: Amazon Root CA 1 But I keep getting this error in Postman: “Error: Connection refused” I’ve confirmed it works in MQTT.fx with the same credentials, so I’m wondering: Does Postman MQTT support TLS mutual authentication with AWS IoT Core? If so, what’s the correct way to set it up in Postman?
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asked a year ago406 views
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If i understood your question correctly:
Postman’s new MQTT client does not currently support mutual TLS authentication (mTLS), which is a requirement for AWS IoT Core connections. Although you can upload certificates and keys in Postman, it seems that these are not correctly utilized for mTLS authentication like they are in MQTT.fx (which explicitly supports mTLS).
That’s why:
Your connection works in MQTT.fx (it fully supports mTLS).
Your connection fails in Postman (Postman’s MQTT implementation doesn’t support mTLS for client authentication yet).
What you can do instead:
Use MQTT.fx (or other mTLS-supported clients like mosquitto_pub/mosquitto_sub) for testing AWS IoT Core.
Use AWS IoT Core’s MQTT test client (via AWS Console) for simple testing.
Use the AWS CLI with iot-data commands for quick payload tests (though this bypasses the MQTT protocol).
Postman’s MQTT client is great for plain username/password or unsecured MQTT brokers, but not for AWS IoT Core’s strict mutual TLS setup.
answered a year ago
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