Method for obtaining internet protocol ip address of terminal device, device, and system

A method for obtaining an internet protocol (IP) address of a terminal device, wherein the method comprises:

• sending, by an application function network element, a first event registration request to a capability exposure network element, wherein the first event registration request is used to request to obtain an IP address of a terminal device in a group;
• receiving, by the application function network element, a first event notification message from the capability exposure network element, wherein the first event notification message comprises an IP address of a first terminal device in the group;
• and
• sending, by the application function network element, a first message to another terminal device that is in the group and to which an IP address has been allocated, wherein the first message comprises the IP address of the first terminal device, an identifier of the first terminal device, and a group identifier of the group.