I want to develop a site as www.logmein.com,I have already completed the user registration part of this site,but unable to develop the actual feature of this site i.e On-demand remote Access. anybody can help
thanks

That is really difficult to do !... why do you want to develop that site ?

It is not just a website(which mainly uses http )!
If anyone gets some idea to make please free to share..

LogMeIn remote access products use a proprietary remote desktop protocol that is transmitted via SSL. An SSL certificate is created for each remote desktop and is used for cryptographically secure communications between the remote desktop and the accessing computer.[1]
Users access remote desktops using an Internet-based web portal and, optionally, the LogMeIn Ignition stand-alone application. The portal also provides status information for the remote computers and, optionally, remote computer management functions.
The service connects the remote desktop and the local computer using SSL over TCP or UDP and utilizing NAT Traversal techniques to achieve peer-to-peer connectivity when available.

From the page
http://en.wikipedia.org/wiki/LogMeIn