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ypant00's profile

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Thursday, January 17th, 2019 7:16 PM

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MQTT Ports blocked while using ATT 4G LTE cell network

I am trying to connect to an MQTT broker in the internet via ATT 4G cell network. I am not able to ping the host as well as connect to the MQTT broker using ports 1883, 883, 443, 8443, 80 and 8080. 

 

If I disconnect from cell network and use wifi, then the server is pingable as well as I can establish connectivity with the server. 

 

I also do not have any problems while using a reseller's (MVNO) network that utilizes ATT network (it uses reseller specific gateway). Has anybody else encountered similar issue? How should I about resolving this issue?

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1 Message

4 years ago

Yes same issue.  I can use the mqtt port for TLS (8883) with my cell phone as a hot spot (with verizon), and on any traditional wifi and I can connect to the mqtt endpoint (Azure IoT Hub). When I use the at&t hotspot (Unite 770s) it doesn't work- it specifically fails when it attempts to communicate via the mqtt port.  My device (rasp pi 4) can use internet and whatever else while using the hotspot, but cannot connect to mqtt broker.  

 

What I know:

Whien trying to connect to Azure (Microsoft) IoT Hub via mqtt port 833: The device (rasp pi4) works fine. The code works fine. Verizon cellular hotspot works fine.  Wifi works fine.  Unite 770s doesn't work- I put my device in the DMZ, I port forwarded both 1883 and 8883 on the hotspot just in case. Made my local IP address static so my pi was definitely in DMZ and port forwarded.

 

What I don't know:

If gms vs cdma is the issue (cell network type), if another mobile hotspot device would work better while still on at&t (I have two unite 770s and neither work), possibly related to 4g vs 5g? I don't know.  And there may be other variables I'm not thinking of.

New Member

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2 Messages

4 years ago

I have a similar issue.

 

MQTT appears to be blocked, or at least impaired on the AT&T network. 

 

I have tested with multiple IoT devices (ESP32/Raspberry Pi) all connected to Azure IoT endpoint. 

 

They both fail when attempting to establish an MQTT connection to the cloud. The port appears to be blocked. 

 

Can someone at AT&T please shed some light on this issue? No issues with T-Mobile or any other international carrier that we have used. Seems like an odd thing to do given the growing usage of this IoT protocol.

 

 

2 Messages

3 months ago

Hi @ypant00 , @RyanM2 , @ajcappon ,

it could be that the ATT network limits the packet size at around 1400 bytes.

Hence when MQTT tries to connect, some messages in the handshake are bigger than that and dropped by the network.

If you have a chance, try reducing the MTU size (Maximum transmission unit) on the MQTT broker server.

Best

(edited)

ACE - Master

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10.4K Messages

3 months ago

@gusgonnet  You are replying to 2 and 3 year old threads.  If you have a specific question, please start a new thread.

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