Unique identification of OC server access

Hello All,

New forum user here, just in the process of deploying OC on a Raspberry 3.
Actually I use multiple RPIs online to do different things. (www-weatherstation, my web server etc). Now another one is going to run OC. As server topology I have one RPI configured as the www dispatcher using the nginx 'proxy_pass' functionality.

    location /some_regex_pattern {
            proxy_pass; # address of target machine

What I need now is a unique pattern to identify OC traffic so that I can send it to the target machine. Could one of the experts help here, please?