In Chataigne you will find this module under "Software" and "Community Modules" with the name of "Reaper-OSC" !
You must activate OSC in the Reaper's Preferences. You can use the "Default" OSC-Configuration file.... or create your own Custom-File and customize all the OSC-Addresses if you want to do so.
You will find more informations here : http://www.cockos.com/reaper/sdk/osc/osc.php
The OSC-Remote-Port can be 7000; the Local Port for feedback from Reaper can be 9000 or any other...
Please be aware that, when you change any values in the Parameters (BankTracksCount, SendsCound, FxCount etc etc) you must save the Chataigne-Session (cmd-S) and reload the file (cmd-shift-O) ! Please note also that "Track-Numbers" for the "Track-Actions" are always "relativ numbers" in relationship of the actual active Bank !!
Have Fun...
To learn more about Chataigne, please visit : http://benjamin.kuperberg.fr/chataigne/
And Ben's Youtube channel where you can find tutorials : https://youtu.be/RSBU9MwJNLY