A method of testing is suggested, based on memorizing the times when a switch point in the communication channel is passed by a signal from a computer network user and by the acknowledgment signal from the other communications user. The time interval based on these time points is compared with the known, interval corresponding to normal operation; if the result is larger than normal, the communication channel is disconnected. The time relationships for the method are given, with an illustration demonstrating the efficiency of this the procedure of monitoring the operation communication channels in computer networks.