Azure IoT Hub connect error from node cannot read property 'write' of null

Azure IoT Hub connect error from node app - cannot read property 'write' of null in amqp libs

Quickly setting up an Azure IoT hub this evening and wiring up some node services to play with, and read the device-to-cloud messages had me stumped as I would get this error intermittently

  stream.write(buffer, callback);
        ^
TypeError: Cannot read property 'write' of null

Turns out it may be the connection string I was using

Connection String causing timeouts  

So I was defaulting to this format

HostName=somewhere.azure-devices.net;SharedAccessKeyName=iothubowner;SharedAccessKey=<yours>

This would cause the error above intermittently, and I wanted to resolve it.

Turns out you can use another connection string format:

Endpoint=sb://yourshere.servicebus.windows.net/;SharedAccessKeyName=iothubowner;SharedAccessKey=;yours;EntityPath=yourEntityPath;

To find these values, go into Azure, go to your IoT hub, Messaging, Endpoints and click on the Events endpoint below:

A properties window will appear.

The Event Hub-compatible name goes in the yourEntityPath value.

The Event Hub-compatible endpoint is where you would enter the Endpoint.

I found the problem and resolution here. I haven't encountered the error "Cannot read property 'write' of null" again.

IoT is way more fun than the old days when I used to send frames down the serial port, using c++, or getting values from a PLC or a weigh bridge. Probably even more fun than the Win SC API. But working with those devices is always good fun.

Cheers

Quintes

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