A method of identifying proximate client devices (1, 2) comprises the steps of: providing a sensory identifier, the first device (1) detecting the sensory identifier and sending a first request message (RQ1) comprising a first representation of the sensory identifier to a matching unit which is preferably part of a correlation server (5), the second device (2) detecting the sensory identifier and sending a second request message (RQ2) comprising a second representation of the sensory identifier to the matching unit, and the matching unit comparing the first representation and the second representation and sending an acknowledgement message (AC1, AC2) to each of the first device (1) and the second device (2) if a match is made. Each request message (RQ1, RQ2) contains a pointer to at least one property of the respective device (1, 2). In addition, the matching unit applies matching rules relating to the properties to limit the number of possible matches.