You can’t connect 2 systems, because they may be running at slightly different rates, because they use different hardware clocks etc.
You have to memcpy the data across by using a custom DSP, one that buffers data, and the other that receives it. Because this may introduce latency because you’d have to double buffer it, you’d have to delay the output of the source signal by 1 buffer to compensate.
Next, because the rates might be slightly different as I said, it would probably be worth using playDSP on the receive side, which is adjusted slightly with setFrequency based on drift. You may not need to do this on your setup, but you could try without it first.