Blackmagic Design ATEM switcher has no TCP interface for easy integration with AV-systems, so SKAARHOJ has created this tool, the ATEM-TCP Link, which provides just that: A simple TCP interface to almost any feature in the switcher.
It will report state changes of the switcher and accept and forward commands to the switcher.
Exactly what you need for AV projects with various AV systems like Crestron, Extron and so forth. Connect to the device via TCP, then change the desired command on the ATEM switcher and the ATEM-TCP Link will output in the terminal how the command looks that you can use to send the same command to the switcher. All of this and more is demonstrated in the video.