I've developed an IoT device utilising OpenWrt so my design needs run a on a shoe-string budget of resources.
I need to be able to push small amounts of data, up to 300bytes to my app on a very irregular basis, something once a week and other time maybe 10 times a day, so I'm not looking to over-engineer this thing, but I do want it to be well engineered. I don't run a web server, app server nor java on the device and everything else is coded 99% in ANSI C.
Now I need to develop a mobile app to push these 300bytes to the IoT device and I'm procrastinating on the design. I'm interested in others'opinions on how best to proceed. I've considered a daemon that listens on a UDP port for a basic bytestream with a checksum, but I worry about security even though the IoT device sits on an Intranet. If I add TLS that's a lot of work for very little use. I could utilise sftp/scp but then I need to run the applicable processes on the device, which breaks with my minimalist design approach.
The 300bytes being sent just need to be appended to the end of a file on the device.
It seems I'm getting caught up in my head so I'd appreciate any thoughts.