A method, computer program, and computer readable medium are disclosed for maintaining communication between first and second mobile units communicating via first and second communications networks, respectively. The first and second units include, respectively, first and second protocol stacks and first and second session layers, which interface between the first and second protocol stacks and first and second software components acting within the first and second units, respectively. The first unit includes first communications hardware with associated drive routines for different communications networks. When the first unit switches from a first to a third communications network, the first session layer maintains communication by selecting the first communications hardware and drive routine required for the third communications network. The identities of the first and second units are maintained by the first and second session layers and retained during the first unit's switching of communications networks.