How are you transmitting the RS232?
If over TCPIP, does the Serial server allow multiple client connections?
Is the serial command specifically OPEN with a separate command for CLOSE?
(some projectors use the same command to open and close - so you could see what might happen if you are sending 2 commands…)
(assuming TCPIP serial server)
Personally - I would only use ONE Mac at a time to send the command…
Probably test to see what happens if you send 2 commands at exactly the same time.
Are they ignored? received sequentially?
Only way of knowing is to test…
S