OTGW on remote pi with ser2net

Now I am building my own domotica system with Domoticz, I bought and built a open therm gateway (OTGW) to intercept and modify the communications between my boiler and the Honeywell Round thermostat I have in the livingroom.

The situation is as follows, I have a rPi in the basement, connected to an RFLink and the smart meter. (The water meter is on the to-add list.) In the attic I have a rPi running some other software and a Synology NAS. The latter fails in running Domoticz and device sharing seems tedious with two different devices so I went with the pi.

Connected everything, setup device sharing per the manual and everything went fine. Or so I thought. Every time I changed the setpoint on the master Domoticz, a new device called ‘setpoint’ would appear on the slave and the setpoint would not be changed on the thermostat/boiler.
Googling this problem got me on two tracks: Write a script on the slave that fixes this or use the OTGW remotely via SER2NET. I chose the latter because I dind’t like the extra software on the pi in the attic anyway and this seemed less of a hassle.

Installing ser2net

SSH into your device and enter the following:

sudo apt update
sudo apt upgrade
sudo apt install ser2net -y

Find out where your OTGW lives and enter:

dmesg | grep tty

To be honest, I couldn’t make out which was the OTGW but since the other USB device is a hdd, I made an educated guess and it worked. I went with /dev/ttyUSB0
Next we will edit the ser2net config by opening the file.

sudo nano /etc/ser2net.config

In this file at the bottom, enter:
which breaks down into: ‘PORT:STATE:TIMEOUT:DEVICE:OPTIONS’ where 0 disables timeout and our options are the baudrate, parity, number of stop bits and number of data bits

Next, add a hardware device to your domoticz choosing ‘OpenTherm Gateway with LAN interface’ for type and connecting to the IP of your device and the port (4000 in our case*) you specified.
Allow new devices for 5 minutes and you’ll see the devices come to your Domoticz server!

* Don’t forget to open this port in your firewall if you have any. In case of UFW

sudo ufw allow from to any port 4000 comment 'Allow OTGW ser2net on local lan'

Have fun!