How to make voip calls from java web application

Following is my use case:

I am developing a web application using Java/J2EE. My application will have registered users and any one of them should call each other at any time. I don't have any problem even if i have to use some proprietary solution/API, but i don't want user to install anything like skype on their systems. What can be the possible solution?

Regarding calls:

1. Laptop - Mobile phone calls Can it be possible that one user uses his laptop/system to p开发者_运维问答lace calls to the other users mobile?
2. Laptop - Laptop (voip calls). In this case, both will use headsets, like we do in GTalk.

Please suggest.

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I am not a J2EE developer, I'm more into .NET. If I have a web app and I need to have a voip functionality there are several ways this can be achieved: 1) Use a 3rd-party component like Netviewer. 2) If you would like to develop the component yourself and you want it to be interoperable then use one of the open source protocol stacks available out there (there are many) that is based on SIP or may be H323, surely there are some for Java. 3) If you don't need inter-operability then you can create your own protocol stack on top of TCP.

I will do case 2 and 3 as ActiveX components to be embedded in the web page.

For VoIP calls the 3 solutions above are suitable. However, if you need to make VoIP to mobile calls then you need a PBX data switch like one of those from Cisco that can route your VoIP traffic to the telephone network. Checkout Asterisk, it's open source.

Netviewer link http://www.netviewer.com/en/

Java SIP https://github.com/usnistgov/jsip

Asterisk Opensource Telephony Projects http://www.asterisk.org/