Hi,
The problem is that IIS may not have permission on that particular port and ASP.NET run as a Worker Process. Once a request comes, IIS will create a new worker process and after completion it will be destroyed. So using ASP.NET you can't make a persistence connection.
This can be achieved by designing a WCF service that will interact with that port and ASP.NET application will communicate with that WCF service.
I have 8.5 years experience in ASP.NET, C#, WCF and SQL Server.