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Distance for the Node to connect to the gateway MQTT-SN ?

Giang

Hi all,

I have a question.

When I try send message coap, it can send as mesh network.

But when I send search gateway msg, connect msg from publish (subscribe) Node to NCP. Seem it can't send as mesh network. I have to put Node in the coverage area of ​​NCP then it can discovery and connect to Gateway. If I put NCP --> Node 1 --> Node 2 in a straight line. Node 1 can connect to mqtt gateway, but node 2 can't . But I can ping from Node 2 to Node 1 and NCP. 

If I connect Node1 and Node 2 to MQTT gateway and put NCP --> Node 1 --> Node 2 in a straight line. I can send data from Node 1 and Node 2 to NCP as mesh network. 

I check message type of discovery and connect message. I saw it same with coap message. They are all used otUdpSend.

So Why is there such a difference?

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  • 0

    I've been working on the Thread and MQTT-SN in combination with the nRF52840 for a while now and started out from the SED examples provided, I'm using the paho gateway and everything works fine when SED nodes are directly connected to the border router for gateway discovery. Now I'm running into similar issues that nodes cannot discover the gateway if they connect via another router node(so there is one hop in between the node that wants to join and the gateway). The SEARCHGW message is send successfully and gateway replies with a GWINFO broadcast, but the node trying to connect never seems to get this broadcast message and give a gateway search timeout response. 

    This severely limits the use of Thread, as only direct links to the gateway are currently possible. Even with radio RX on when idle the node doesn't seem to receive the broadcast message send to ff03::1, what could be causing this?

  • 0 in reply to LucD

    I've just setup a network sniffer and the GWINFO msg is broadcasted with hoplimit = 1, I assume this will prevent if from reaching any nodes down the network tree. How can this setting be changed? I don't know if this is hardcoded in the ncp firmware, set from the OpenThread Border Router software or something in the paho MQTT-SN gateway config. 

  • 0 in reply to LucD

    Adding some lines the paho MQTT-SN gateway code to set the multicast hop (in my case I picked 5) fixed the issue, as the default value is 1 if you do not set this option and thus the GWINFO message doesn't get broadcasted past the initial hop.

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