Method and system for setting a session between converged ip messaging service client and short messaging service client

A method and a system for establishing a session for message communication between a CPM(Converged IP(Internet Protocol) Message) client and an SMS(Short Message Service) client are provided to establish a session for interactive message communication between a CPM client and an SMS client. If a request to execute interactive message communication with an SM(Short Message) client is inputted, a CPM client transmits an SIP INVITE message to a CPM server in order to establish a session to execute interactive message communication with the SM client(501). The CPM server confirms whether the receiver of the SIP INVITE message does not use a CPM service. If so, the CPM server transmits the SIP INVITE message to an IWF(Interworking Function)(503). The IWF checks subscriber information corresponding to the receiving client of the SIP INVITE message. If it is confirmed that the receiver is only an SMS user who doesn't use any other messaging services, the IWF converts the SIP INVITE message into an SMS-SUBMIT message and transmits it to an SM server(505). The SM server converts the SMS-SUBMIT message into an SMS-DELIVER message and transmits it to the SM client(507). In response to the SMS-DELIVER message, the SM transmits an SMS-DELIVERY-REPORT message to the SM server(509). The SM server transmits the SMS-DELIVERY-REPORT message to the IWF(511).