Two separate 24 track units in sync

Hi Dan
I have a simple question:
I need to use two u24 units in a live environment, the first one is the main unit (I use only 9 tracks), the second one should be a spare unit with the same channels of the first one. The signals are connected both to a Radial SW8 switch and DI box, using one db25 connector each (8+8 channels). The 9th channel is coming out from the first unit only, and the track is a simple 1 KHz tone, feeded from out 24 (I have a second db25>TRS connector for this signal).
The main problem is to send to both devices the same transport command (play and stop), also if the two devices are not exactly frame synced. If the first device fails, the second should continue to play (and the Radial SW8 switches the signal to the second device).
The question is this one: how could I send the same play stop transport command to both the devices? I don’t like to use the external play/stop jack to perform this, I prefer to use the main device as master player using his front controls or also a computer connected in wifi or better, via rj45 cable (seems not possible, but maybe using a router I could connect two devices to one computer…..)
The only thing I’ve see, is the received ip address and the port (55000), using Wireshark and the uRemote app, but I don’t have other protocols data about the transport commands. Note, I can program my own software using MaxMSP to perform this kind of task.
Can you help me in any way? Many thanks. Italo Lombardo (keepsound-at-tin.it)