[ros-users] Interfacing to ROS from external software

I want to develop a piece of code that can communicate with ROS without using any (or minimal) ROS libraries. With Player-Stage, I used to be able to use open a TCP/IP connection with the player server and communicate using XDR format messages. What is the best way to interface with a ROS system from an external software?

Basically we will be receiving a ROS system from a university and it will run on a separate PC. We would like to build a C++ software block that can sit on a remote machine and send commands to and receive telemetry from the ROS system.

Thanks
GP