I am working on a web based application where users will use their webcams for realtime Video call on web browser (kinda Webx). Is their any way that the web application can identify if any (tcp/udp/https) application/service  is using the video service and consuming the network bandwidth so that I can  show a message to the user -  "Please close skype or gtalk and then to proceed with the video call". 
In short; how to identify skype like service which is holding the webcam via web application and alert user to close that app first.
Your web application can not know if there is a video service like Skype that is running on the same host than the browser, but your application can simply run a speed test, to check for the currently available bandwidth between the browser and your server. For instance, you can do that easily writing some AJAX code that automatically starts downloading a big file (using XMLHttpRequest()) and stops after 10 seconds (using XMLHttpRequest.abort()). You can monitor the throughput using progress events. Then, if your app find that there is not enough bandwidth, you may ask the user to stop network applications.
Way to identify tcp/udp/https service holding the webcam and port