A method and apparatus for communication between a mobile computer terminal and a host computer in a system in which it is necessary for the mobile computer terminal to send a message to the host computer at a particular time. The specific time at which the mobile computer terminal must send a message to the host computer is first determined. Then, a timer or clock is programmed to wake up the mobile computer terminal at the specific time. A sleep mode may be entered, which may be interrupted at the specific time to send the message. This will normally allow a mobile computer terminal to maintain its lease on an IP address despite being out of range of a wireless network.