Abstract: A system, method, and program for establishing modem communication between a master computer system and a plurality of slave computer systems coupled to a common serial communication channel are disclosed. An unique identification number (UIN) is assigned to each slave computer system. The slave system modems are initialized to a “receive mode.” The master computer system directs a session request to the slave computer systems through the common serial communication channel. All slave computer systems receive and respond to the session request by changing each of the modems to the “answer mode.” After all the slave computer systems respond, the master computer system requests communication with a particular slave computer system among the plurality of slave computer systems. The master computer system uses the UIN to establish communication with the particular slave computer system by sending a request from the master computer system specifying the UIN of the particular slave computer system.