In a communication system for establishing the communication between a radio intelligent terminal and a server via gateways, it is necessary to notify a non-communicating and a disconnecting radio intelligent terminal of an address of an exchange-destination gateway at the time of changing from a gateway to be used at all time to an exchange-destination gateway for some reason. To achieve the above object, a communication system comprises address notifying means for notifying the radio intelligent terminal of the address of the exchange-destination gateway according to a gateway exchange instruction inputted by an operation. The address notice is sent to the non-communicating terminal at the time of inputting the gateway exchange instruction, and is sent to the disconnecting terminal when it can start the communication.