Abstract: A communication method between an IP terminal and a client is provided to simplify a task for installing an IP terminal in an IP network by improving a communication method between the client and the IP terminal, a communication method between an IP terminal and a client over an IP network without the port mapping or port forwarding of an IP sharer, and a communication method between an IP terminal and a client, which enables even an ordinary person without specialized knowledge to install the IP terminal because the port mapping or port forwarding of an IP sharer is not performed.

Abstract: Provided is a door lock system, which can control a door lock using a user's own terminal without regard to kinds of the user's terminal and mobile service providers that the user's terminal has been registered. The door lock system includes: an entrance door provided at one side of a building; a door lock provided at one side of the entrance door for controlling opening and closing of the entrance door; and a terminal for providing a communication signal to the door lock through communication with the door lock.