Control of access to an on-line service, the access to the service being requested, via a communication network, by a terminal suitable for receiving data broadcast by a plurality of devices for data transmission by light modulation producing a light beam. In particular: each transmission device is characterized by a unique identifier; and each transmission device belongs to a group of devices. The following steps, carried out by a server connected to the transmission devices, are provided: upon receiving a request from the terminal to access the service via a second transmission device identified by a second identifier, verifying whether a previous access request for said same terminal was accepted for a first transmission device identified by a first identifier; and, when the first and second identifiers correspond to devices of the same group, processing the access request.