A communication system and a method of transmitting and/or receiving data in the communication system are provided. A method of transmitting media data of a camera to a user terminal in a communication environment in which the camera connected to a first network and the user terminal connected to a third network are connected to a second network includes: obtaining second address information of the second network that corresponds to first address information of the first network, from an address conversion apparatus; obtaining third address information of the second network from an address providing apparatus connected to the second network; transmitting the first through third address information to the user terminal through a session control server connected to the second network; and transmitting the media data to the user terminal based on at least one of the first through third address information.