To easily obtain whether or not registration information of a communication terminal is registered in a server system.

The communication terminal includes: a registration request transmitting part for transmitting a registration request to the server system; a confirmation information receiving part for receiving confirmation information which indicates the registration of registration information by the server system; a communication part for communicating with another communication terminal via the server system; and a display part for displaying a first display form, which indicates that the registration request is not transmitted yet and the registration information is not registered in the server system yet, till the registration request is transmitted, displays a second display form, which indicates that the registration request is already transmitted, in a period from registration request transmission to confirmation information reception; and displays a third display form, which indicates that the registration information is registered in the server system, after receiving the confirmation information.

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