Patent ID: 7415639

Claim:
An apparatus for monitoring the reliability of a data link for a data transmission between a server data processing apparatus and a client data processing apparatus, the apparatus comprising: a server application program is run on the server data processing apparatus, which server application program comprises: a first control unit for generating control data, and a second control unit, a client application program is run on the client data processing apparatus, which client application program comprises: a representation unit for generating image data for representing an image on a client display screen which is connected to the client data processing apparatus, and a test unit, a data link over which the server application program and the client application program exchange data, the representation unit being configured to generate, in dependence on incoming control data, image data to form a control representation on the client display screen, the first control unit being configured to: triggered by a trigger signal, generate first control data after the arrival of the trigger signal and for a predetermined running time which starts anew at each trigger signal, the first control data generating a first control representation on the client display screen, which first control representation optically informs the user of the existence of a reliable data link, generate second control data after expiration of the running time, which second control data generates a second control representation on the client display screen which optically informs the user of the absence of a reliable data link, the second control unit being configured to carry out a test procedure during which the second control unit periodically transmits a test message to the test unit, the test unit being configured to return, in dependence on the incoming test message, this test message or a different test message to the server application program, the first control unit further being configured to: be triggered in the context of the test procedure only if the returned test message is in order, and the second control unit being configured to repeat the transmission of the test messages with a time period shorter than a running time during which the first control unit generates the first control data.