A method of establishing a communications session for communication of data with respect to at least two user devices in a data communications network. A client-server connection request is received from at least one of the at least two user devices. Call party details of a telephone call are received. The telephone call involves at least a first telephony user device and a second telephony user device. The call party details include a first identity associated with the first telephony user device and a second identity associated with the second telephony user device. At least one of the first and second identities comprises a telephone dialing number. A separate communications session is established on the basis of the first and second identities received in the call party details.