Hello..
As per your requirements I have a team of tech savvy developers and programmers to create web based chat applications with PHP and Jquery, CSS .NET, C#, VB.NET and AJAX style features. Our team has worked on multiple projects related to live chat servers and can easily mockup server vulnerability.
You can also view our work portfolio in my profile. Please reach out to me so we can have further understanding regarding your project.
Thanks have a good day..