According to one embodiment, a communication system includes a Network Address Translator (NAT) rooter and a telephone exchange apparatus. The NAT router comprises a transfer module configured to transfer a communication packet brought from the global network to the telephone exchange apparatus. The telephone exchange apparatus comprises a memory configured to store a map table in which a terminal ID specifying the terminal, and an address and a port number specifying the network are correlated with each other, and a controller configured to refer to the map table, and notify the terminal connected to the global network of an address and a port number of the telephone exchange apparatus's own apparatus as an address and a port number of the communication partner, and bring the communication path between the terminals into the apparatus.