The invention relates to a method for managing data transmissions via an internet network (RI) between calling (Aa) and called (Ab) subscribers and also an associated smart card. A card (2a) cooperates with a terminal (1a) and has client/webserver (S.sub.WEB), CGI and proxy (27a) functions. The proxy function is used for the signaling channels (CS) and data channels (CD). The terminal (1a) and the card (2a) include specific communication protocol layers that make it possible to establish sessions for bidirectional transmission between them and/or with the internet network (RI). The smart card (2a) stores applications associated with protocols for listing (900a) and for locating subscribers (901a), as well as subscriber profiles (903a). It plays the role of a proxy in the signaling channel (CS) and/or data channel (CD).