websentry-mitm-prometheus-exporter

README

WebSentry MITM Prometheus Exporter

This is a server that intercepts traffic from a WebSentry dehumidifier (as supported by the various https://dehumidifiedairsolutions.com/ brands) and parses the traffic while proxying it upstream to its cloud service.

It then exports Prometheus metrics so I can see things more detailed in Grafana than I can on the official cloud portal.

Protocol

See the protocol details page for what I've figured out so far. If you figure out more, file an issue with details! (Or let me know if this is an existing protocol you recognize.)

Using

To use this server, you have two main options:

• If you control your LAN's DNS server, add a fake entry for websentry.seresco.net (or whatever brand DNS name your unit queries) and point it at the IP address where you're running this code.

• If you control your LAN's DHCP server, send the dehumifier unit (e.g. 10.15.25.34) a router address to a Linux box running this code (e.g. 10.15.25.2) with an iptables rule like iptables -t nat -I PREROUTING 1 -s 10.15.25.34 -p tcp -m multiport --dports 1030 -j DNAT --to-destination 10.15.25.2:1030. With dnsmasq, you can do something like:

dhcp-host=00:90:c2:XX:XX:XX,10.15.25.34,set:usemitm
dhcp-option=tag:usemitm,option:router,10.15.25.2

Unofficial

This is all just my personal contraption and by no means official. The Dehumidified Air Solutions folk are unlikely to support this

The official way to get these metrics is via MODBUS or LON or BACNET or something, but I didn't want to wire those up. I preferred to use its existing Ethernet connection.

Documentation

Overview

The websentry-mitm-prometheus-exporter is a MITM proxy server for the WebSentry port 1030 protocol between WebSentry-capable dehumidifiers (see https://dehumidifiedairsolutions.com/) and its cloud service (TCP websentry.seresco.net:1030).

Assuming you set up fake DNS entries or DHCP + iptables to intercept the traffic and point it at this proxy, this proxy then relays it onwards upstream, parsing its contents and exposing a Prometheus metrics endpoint that can be scraped by Prometheus.

This is all because I didn't want to wire up yet another MODBUS thingy to my HVAC system.

Disclaimer: this has been tested on exactly one system (mine) and reverse engineered by eyeballing the binary traffic. It may or may not work for you. (Or for me.)

For protocol details, see https://github.com/bradfitz/websentry-mitm-prometheus-exporter/blob/main/websentry-protocol.md