RV50 Serial Modbus

Hi, I’m trying to connect a device (solar charge controller) via serial to the RV50, and then access this data remotely using the cell modem IP address and port. The device manufacturer states that all communication is done using MODBUS RTU, and I selected that option under the serial tab. Do I need to configure port forwarding for this to work? And what other considerations should I make?

Refer http://source.sierrawireless.com/resources/airlink/software_reference_docs/airlink-rv-series—configuration-guide/