Patent ID: 8395652

Claim:
A video conference system comprising: a data network having at least one network computer for communicating audio and video data between a plurality of user computers; a plurality of user sites connected to the data network, each of the plurality of user sites having at least one camera for transmitting streaming video data to all others of the user sites over the data network, having at least one microphone for communicating audio data to all others of the user sites over the data network, and having at least one of the user computers for receiving streaming video and audio data from others of the plurality of user sites over the data network; a user presence application running on the at least one user computer at each of the plurality of user sites for identifying others of the plurality of user sites participating in the video conference; a shared file stored on the data network and including a list of the plurality of user sites that are participating in the video conference, the shared file having a current property; wherein the at least one user computer at each of the user sites is configured to communicate a file modification status request to the at least one network computer, the file modification status request including at least a file identifier identifying the shared file and a property; and, wherein the at least one network computer is configured to receive the file modification status request from each of the user computers and to perform steps comprising: use the file identifier from the file modification status request to identify the at least one shared file; identify a current property of the at least one shared file; and, compare the shared file current property to the property from the file modification status request and communicate a response to the at least one user computer when the file current property does not match the property from the file modification status request.