Abstract: Provided is a data communications management system which enables the use of conventional network applications across mobile communications links, addressing the problem that these applications (which are written for fast, reliable and cheap wired connections) are not well adapted for mobile communications. A set of call handler components are provided for each of a plurality of different network communication applications, and a call manager component which intercepts and analyses all communication calls from applications on the local system and redirects them to the appropriate call handler. The call handler then performs functions transparently impersonating the remote target of the communication, and replaces the initial protocol of the call with a different protocol which is optimised for the particular service. In some cases, a second call handler is provided at the remote end which replaces the protocol again before delivering the call to the target.