Use a latching relay. Here is one I found on Amazon. https://www.amazon.com/dp/B015MRQNXS/?coliid=I3LXTGKX4GEPUR&colid=31WWM91JAUE22&psc=1&ref_=lv_ov_lig_dp_it
If you are trying to use with existing 3 ways use https://www.amazon.com/dp/B015MSYQ8Q/?coliid=I3RP8X9OMYWU97&colid=31WWM91JAUE22&psc=1&ref_=lv_ov_lig_dp_it
Use an optocoupler to indicate lamp status...see the last diagram in this post. https://forum.arduino.cc/index.php?topic=435506.0
You should not typ "\n"!
It means that you should press enter on your keyboard.
On Linux I saw that I have to send "\r\n" instead of "\n".
"\r\n" (Carriage return, Line feed) is the Windows return, "\n" only the Linux return.
Do you have interest to try OH2 together with MySensors Ethernet Gateway to get working?
I do not have enough force to push developers to make this happen. At the moment there is some problem on this, because full control is not possible. I think that MySensors Serial Gateway is working with OH2, but I don't like to use it. I like to connect my devices into LAN not cabling via old fashioned way using serial wires.
OK, it's beginning to become clear. My initial gadgets & gizmos should arrive today, so I'll start tinkering, and I'm sure more clarity will come.
Thanks for the quick responses, and for your patience. This is so far the best HA forum I've found anywhere!
