Is it possible to fix the client's LWM2M port on the nRF9160?

RE: Is it possible to fix the client's LWM2M port on the nRF9160?

RicardoCarvalho — Tue, 21 Nov 2023 16:27:21 GMT

Hi Achim,

Anyway thanks for the help!

I think the best option would be to change the server to a more 'standard' operation instead of having to make changes to the SDK.

Regards,

Ricardo

RE: Is it possible to fix the client's LWM2M port on the nRF9160?

Achim Kraus — Fri, 17 Nov 2023 19:06:37 GMT

I don't use the approach with bind() so I don't have the details by hand. But you will find a lot of examples searching the web.

RE: Is it possible to fix the client's LWM2M port on the nRF9160?

RicardoCarvalho — Fri, 17 Nov 2023 18:39:32 GMT

Hi Achim,

Thanks for the detailed explanation!

I thought it would be a matter of settings, the last thing I wanted was to change the SDK's lwm2m library 😟

Regarding bind(), I thought it was only used on the server...
How is it used on the client?
I assume it will be before connect(), but what is the sockaddr passed in bind()?
Is it the "(client IP):(port I want)"?

Thank you for your help!

Regards,

Ricardo

RE: Is it possible to fix the client's LWM2M port on the nRF9160?

Achim Kraus — Fri, 17 Nov 2023 13:13:18 GMT

Hi Ricardo,

the answer has unfortunately two parts:

1. (the good one): you may chose a local port by using "bind()".

2. the port your server gets in the received packet may still be a different one.

I haven't tested 1, because in my experience, the 2. makes it unattractive.

The 2. is mainly caused by the network infrastructure, e.g. a IP-breakout of your network provider, which then acts a NAT (network address translator). Such network components usually assign your cellular device a temporary public IP-address. Without traffic for a while, that assignment is cleared and may be reused by other devices.

So, which local ip-address does your device report? And which device ip-address does your server report? You may also ask your mobile network provider, what's used there. Some are offering so called "private networks", which then requires a "ip-tunnel" in order to connect you server to that "private network".

If you use DTLS 1.2, then DTLS 1.2 CID may offer you an alternative solution. The LwM2M server must support that as well, because for LwM2M it's not only the DTLS layer, which needs to consider the client's ip-address.

RE: Is it possible to fix the client's LWM2M port on the nRF9160?

RicardoCarvalho — Fri, 17 Nov 2023 11:40:54 GMT

Hello Amanda,

Maybe I didn't make myself understood... I need to define the port of the client (device) not the server. The port that the server uses to talk to the client.

When the LWM2M client makes a registration request to the server, it indicates the port that the server will have to use to talk to this client, it is this port that I wanted to know if it can be defined.

Thank you for your help!

Regards,

Ricardo

RE: Is it possible to fix the client's LWM2M port on the nRF9160?

Amanda Hsieh — Thu, 16 Nov 2023 14:39:45 GMT

Hi,

You can set the fix port with CONFIG_LWM2M_CLIENT_UTILS_SERVER:
Choose the LwM2M server you wish to connect to. Address must be full URI containing protocol and port numbers, unless it is same as CONFIG_LWM2M_PEER_PORT. For example "coaps://server.example.com:5684". Protocol must be "coap" when no security is used, or "coaps" when DTLS is used.

Example: https://github.com/nrfconnect/sdk-nrf/blob/v2.5.0/samples/cellular/lwm2m_client/prj.conf#L91

Regards,
Amanda H.