A modular adapter is attachable to an avionics box of an aircraft to enable network communication between the avionics box and other avionics boxes or controllers on the aircraft, local computing devices, and/or remote computing devices or remote servers in an external network, such as an Internet. The adapter includes a microserver module having a web-based server, a computer processor and memory, a data-over-power module configured to connect to a power connector that delivers power to the avionics box and transmits data to the microserver module, a connector module configured to plug into a power port of the avionics box such that power delivered by the power connector passes through the adapter to the avionics box, and a test port connector configured to plug into a test port of the avionics box. The test port connector enables the microserver module to access data from and send data to the avionics box.