Problem

The NOx and O3 sensors support the Modbus protocol on the privileged port 502. The Loyola firewall blocks this privileged port.

Solution

Before accessing the sensors from outside the Loyola network, create the required SSH tunnels as follows:

ssh -L 9502:147.126.68.251:502 -L 9503:147.126.69.218:502 xenon.cs.luc.edu

Then you can access the NOx and O3 sensors at localhost:{9502,9503}, respectively.