Method and system for automatically resuming call after network handover

A method for automatically resuming a call after network handover, the method comprising:

• registering, by a first terminal, with a server through a first network, and registering, by a second terminal, with the server through a second network;
• sending, by the first terminal, a call request to the second terminal via the server, and responding, by the second terminal, to the call request through the server and establishing a call with the first terminal;
• and
• during the call between the first terminal and the second terminal, when the first terminal is handed over from the first network to a third network, first storing, by the first terminal, call resources, then registering with the server through the third network, constructing a resume request according to the stored call resources, and sending the resume request to the second terminal via the server, and resuming, by the second terminal, the call with the first terminal according to the resume request,
• wherein a specific process in which the first terminal stores the call resources comprises:
• storing, by the first terminal, first call signaling used to establish the call and second terminal information, the second terminal information being a name of the server with which the second terminal registers,
• wherein a specific process in which the first terminal constructs the resume request according to the stored call resources comprises:
• constructing, by the first terminal, call transfer signaling according to the stored first call signaling, first terminal information, and the second terminal information, the call transfer signaling being the resume request, and the first terminal information being the name of the server with which the first terminal registers through the third network,
• wherein the method further comprises:
• sending, by the second terminal, second call signaling according to the call transfer signaling and transmitting the second call signaling to the first terminal via the server, and re-establishing, by the first terminal, the call with the second terminal according to the second call signaling,
• wherein the constructing of the call transfer signaling comprises:
• constructing, by the first terminal, a Call-ID and From and To header fields of the call transfer signaling according to the first call signaling, constructing a Refer-To header field of the call transfer signaling according to the first terminal information, and constructing a Request-URL header field of the call transfer signaling according to the second terminal information, and
• wherein the method further comprises:
• detecting, by the second terminal, a Refer-To header field of the call transfer signaling after receiving the call transfer signaling, and sending, by the second terminal, the second call signaling when an object displayed in the Refer-To header field is the first terminal with which the second terminal is in communication, a header field of the second call signaling comprising Answer-After:
• 0;
• and receiving, by the first terminal, the second call signaling and performing detection, and resuming, by the first terminal, the call with the second terminal when the first terminal detects that the header field of the second call signaling comprises the Answer-After:
• 0.