Write M code

I need to add M code to control the turning on or off of the laser. I have not contacted linuxcnc before and want to know how to write or run a correct M code

The collet-closer M-code in the examples linked above should work if all you need to do is turn a GPIO pin on and off.

Or, you could use the existing coolant output pins (I doubt that a laser uses "mist coolant") and then use M7 / M9.

Hi, I'm very new to linuxcnc and this forum, so forgive me if this is easy to answer from the documentation. I'm working to build a hybrid 3D printer for metals (DED+CNC) and I'm trying to better understand what custom M code can do. Our printer will have a CNC spindle as well as a laser head mounted together. The laser is controlled using a simple ethernet interface. The laser will be plugged into a router with the desktop and MESA hardware. Is it possible to create an M-code that can be called from LinuxCNC that will allow for ethernet communications with the laser controller? As far as I can tell I can assign an unused M code to run a python function and have two parameters that can be passed. Are there any limitations on this that would prevent me from using ethernet to talk to the laser?
Thank you in advance.