This is the Arduino webserver for OnStep. It provides Ethernet (IP) access to connect to OnStep via command channel and/or website. This works with Sky Safari (tablets/phones,) my OnStep Android App, and my ASCOM driver (PC.)
For my testing I used an Arduino M0 and Arduino Ethernet Shield R3 (W5100.) Other configurations are untested but Arduino's with ARM MCU's and similar Ethernet Shields should generally work. There are reports of the Arduino Ethernet Shield V2 not working with the M0 so aviod that!
Use the Arduino IDE's "Tools->Boards->Boards Manager" menu to add ARM device support.
This source code is inside your OnStep folder under the "src/Ethernet" subdirectory.
Open the Ethernet.ino file inside this folder. Find the "Config.h" tab and make any changes as required for your setup. Upload.
Once the firmware is on the device simply connect the serial interface lines to OnStep's Serial1 port similar to how a Bluetooth module would be connected.