Patent ID: 7990866

Claim:
A connection establishment method, comprising sequential steps of: a first step of transmitting from a client device to a server device a first message requesting establishment of a downlink connection used for receiving data; a second step of transmitting from said server device, in response to receipt of said first message, a second message requesting establishment of an uplink connection used for receiving data from said client device; a third step of transmitting, from said client device which has received said second message, to said server device a third message acknowledging said second message and requesting establishment of said downlink connection; a fourth step of establishing at said server device which has received said third message, said downlink connection based on content of said third message; wherein said first message and said third message each contain sequence number data comprising an initial value of a sequence number of a message, and said fourth step further comprises confirming that said first message and said third message from said client device both originated from a single device based on confirmation that said sequence number data contained in said first message and said third message are identical; and a step of transmitting from said server device to said client device a fourth message acknowledging said third message, said fourth message including information to establish said uplink connection.