Just before opening the COM port, would it be possible to add the line of code "com.DtrEnable = true;" so Smoothieboards know LaserGRBL wants the connection message?

Also, not sure if it's my port of GRBL - but when I'm in Alarm state, I can't connect (seems to time out) but it could be because of the alarm message being sent on connect.

My laser isn't finished yet, so I can't tell if this is a good idea or not at the moment, but running your generated picture gcode on the bare electronics on my desk has long pauses on every "S0" command at the end of each raster line. I can make them go away if I change it to "G1 X0 S0", relative mode means X doesn't actually move, but which tells GRBL to not leave G1/2/3 mode and pause so much.

Thanks.