Patent ID: 8391279

Claim:
A modem connecting a communication terminal and an IP phone with a server, the communication terminal comprising a software phone, the modem comprising a processor, a memory, and one or more programs, wherein the one or more programs are stored in the memory and operable to be executed by the processor, the programs comprising: a communication module receiving a calling request packet from the software phone, wherein the calling request packet comprises a special tag, a source IP address and a source port number, the source IP address is an IP address of the communication terminal, the special tag indicating that the software phone is required to establish a call by employing a telephone number of the IP phone; a determination module determining if the calling request packet comprises the special tag, and determine if the IP phone is idle upon the condition that the calling request packet comprises the special tag; a recording module recording the IP address and the port number of the calling request packet upon the condition that the IP phone is idle; a modifying module modifying the source IP address of the calling request packet to be an IP address of the IP phone; wherein the communication module further transmits the modified calling request packet to the server, and receives a calling reply packet comprising a destination IP address corresponding to the calling request packet from the server, the modifying module further modifies the destination IP address of the calling reply packet to be the IP address of the communication terminal, the communication module further transmits the modified calling reply packet to the software phone so as to establish the call, and the modifying module further modifies the destination IP address of the calling request packet from the server to be the IP address of the communication terminal upon the condition that the IP phone is idle.