The core of Lowell Instrument Group software is based on a client-server model. The server is LOIS (Lowell Observatory Instrumentation System) which controls the hardware and LOUI (LOis User Interface) behaves as the client. The communication between the 2 layers is done via a message broker (Apache ActiveMQ).

In addition to the Java APIs for ActiveMQ, two major third party libraries are used as part of the messaging system:

• SimpleXML - used within java layer for XML serialization
• ActiveMQ CPP - used within the C/C++ layer for communicating with the broker

For trouble shooting, it is very important to understand the messaging architecture and logical layout of the system. Please refer to Messaging Architecture page for more information.