Bi-directional Serial communication?

This is a very fundamental question.
I have two XB24-ZB’s - one configured as a Coordinator, and the other as a Router. Both in “AT” mode. I connect my Router to a serial device that’s outputting data strings a couple of times per second, and those strings show up in the console connection of the Coordinator (via XCTU). All is good.

Here’s the question:
I presume the serial communication is bi-directional? In other words, if I need to issue commands to the serial device attached to the Router, I presume I can do that from the Coordinator (via an Arduino, PC or something similar) over the XBee RF link?

And here’s a complication:
Everything is talking at 9600 baud right now and it’s barely enough bandwidth for the data that’s flowing. I’d like to command the remote serial device (attached to the Router) to change to 38,400 baud - which may be do-able depending upon the answer to the first question. But then I need to command the two XBee’s to change to 38,400 baud. How do I handle that? Do I need to go to API mode? Or can I do it with AT mode?



Yes the XBee modules create a bidirectional link between devices.

To change settings on a Remote module, the module connected to the PC which will be issuing the commands must be in API mode. The one receiving the remote commands can be in either transparent (AT) or API mode.