Communication by a network node in a data network

A method for establishing a communication connection between a network node and a communication partner in a data network is provided The network node receives at least one message from the communication partner via a wireless interface and verification data are attached to the message. The verification data include a transmitter measured data image, representative of measured data acquired by the communication partner in a preceding recording period. The network node verifies the communication partner by a comparison, based on a correlation known to the network node) and/or communicated by the communication partner to the network node of the transmitter measured data image contained in the received verification data with a receiver measured data image, which has been created separately from the transmitter measured data image and which is stored in a data memory of the network node.