IM Client in ASP.NET

Ok guys i think i'm probly dreaming here, given asp.net is server side... but,

What i'm trying to do is create a messaging service using asp.net.... essentially there will be two ways of accessing the messaging service.

1) Web Services : This way will be stateless... users can send/receive messages, but to receive, they basically have to keep updated the page to check for new messages.. this is kind of messy, but i will be using it in some places to access the service

2) TCP Server/Client : There will also be a server attatched to the messaging service. It will take clients, allow them to login, send/receive messages, etc... This way works nice as the server will send the client new messages, etc... the client doesn't constantly have to refresh...

So, i guess what i'm asking, is, is there a way, using asp.net pages to make something similar to my 2nd method? i know i can use sockets in an asp.net page but i don't think the sockets would work in the way i'm wanting them to...

this brings me to remember activex... i know users would have to download the program files for activex, but activex could do what i'm asking... is there some sort of activex counterpart in .NET ???...

the service i'm trying to create would be on a very large scale, hence i don't want a stupid little window that keeps refreshing to receive messages, and i don't want tons of people constantly polling a database.. that would put much strain on the server... i also don't want to make everyone download and install special software...

the fact that i'd like to make this work on mobiles eventually comes into play as well... how would i design for this scenerio too?

i hope someone's already experienced some of these problems that can shed some light for me... thanks guys!