Legacy mqtt vs nx client

[karimelhammady]

What is the difference between the legacy mqtt client and the nx client? What will be the benefits for me to switch to the nx client instead of the legacy mqtt?

[ryanwinter]

Hi @karimelhammady,

The MQTT client hand-crafts the MQTT messages to authenticate and communicate with Azure DPS and IoT Hub. The NX client utilizes the new Azure RTOS middleware C SDK to connect with Azure IoT.

The MQTT client was created before we had a dedicated SDK for connecting an Azure RTOS application to Azure IoT. It's marked legacy as now we have the dedicated SDK, it is no longer the recommended way to connect, as the new SDK provides much more features, optimised memory used and increased stability.

You can read more on the middleware here:
https://github.com/azure-rtos/netxduo#azure-iot

[karimelhammady]

Hello @ryanwinter ,

Thanks for your respond. That makes sense. I tried to switch to the nx_client; however, I faced some issues while trying to connect to the IoT hub, during the TCP handshake. After the certificates exchange, it shows an error message " Encryption alert". Any thoughts what would be the reason for that? Also, if I want to use the Device update Agent, I found a way with using "IoT plug and play", is there any other way to do it while using the nx_client?

[ryanwinter]

Hi,

So for the connection issue, are you using SAS tokens for connection? I dont think the original MQTT sample supported x509 certs so I'm assuming you are. Are you connecting via DPS? If so, then I'm assuming the DPS auth step is correct? Where are you seeing the "Encryption alert" error message, is this on the serial output?

The areas I have seen authentication problems kind of like you are seeing above, are either one of the stack sizes is too small, and seeing some corruption, or perhaps a problem with the ethernet memory pool, either it's too small or something is just not lining up right.

Are you able to share more on the project? Like the device you are targeting, or if there is source code I could look at?

On the ADU front, the team is actively working on ADU integration directly into netxduo, however this is currently in preview and is quite old. It should be possible to continue using your existing method along side using the SDK, as you could intercept the existing PNP topics though.

[karimelhammady]

Hello @ryanwinter,

Thanks for your help, I really appreciate it.

I am using SAS tokens for connections. Also, I am NOT connecting via DPS. I am seeing the "Encryption alert" message when capturing packets using wireshark. The device I am using is SAME70Q20. For now, I am just trying to run the nx_client sample code from the getting-started repository. I have been using the legacy client for a while and it is working fine.

I traced the function that is sending the error message, _nxd_mqtt_process_connack ( ) in nxd_mqtt_client.c.

this also a screenshot of the wireshark capture.

[ryanwinter]

Hmm, this is hard to diagnose, it looks like TLS was successful as the application data has started exchanging, however it looks to have failed at the initial mqtt negotation.

What error response are you getting to the nx_azure_iot_hub_client_connect() call on the serial console?

[karimelhammady]

Hello,

The following error is logged : "IoTHub client connect fail: MQTT CONNECT FAIL status: 65667" . The status code is returned from nxd_mqtt_client_secure_connect ( ) , which is called from nx_azure_iot_hub_client_connect ( )

Thanks

[ryanwinter]

This is coming up with:
#define NXD_MQTT_ERROR_SERVER_UNAVAILABLE 0x10083

So this indicates that the CONACK message is returning this specific code from the server. I'm unsure why the server would be responding with unavailable, let me dig in a little more.

[karimelhammady]

okay, great. I am also checking that from my side. Will let you know if there is any updates. Thanks!

[ryanwinter]

If you want to email me the id_scope and the device_id, then I can look into our connection logs to see if there is any information around what is happening here. My email is rywinter at microsoft.com.

[karimelhammady]

for the id_scope, that is the one for DPS, no? I am not using DPS though.

[ryanwinter]

Sorry, then the "device id" and the "hub hostname".

[karimelhammady]

I sent it. please check your email.

[ryanwinter]

I can see you have a parallel thread in Q&A, cross-linking that here for reference:
https://docs.microsoft.com/en-us/answers/questions/729634/connect-return-error-code-in-connack-message.html