This work aims to contribute to the creation of networks of online laboratories by proposing the model of a scalable and general purpose laboratory server and its integration into the iLabs network. The lab server has been designed to control heterogeneous devices and can be easily adapted to different fields of application. The communications between the laboratory server and the end user interfaces, and between the laboratory server and the devices are completely mediated by web services. The server model has been applied to the development of an online laboratory on Digital Signal Processing. The laboratory is now part of the iLabs network. The task of integration into the network has stimulated the development of a new interface that minimizes the changes to be done on existing lab servers to join the iLabs network and makes integration independent of server technology. The new interface, named LabProxy, contributes to the iLab Shared Architecture (ISA) and has been included in the software repository of iLabs.