i programmed a little webserver (with system.net.socket listening on port 8080) running in the global asp.net application which
is able to handle "long-live" -xmlhttp-requests and support connection-keep-alive (for a better performance).
on my site (mysite.com/chat/default.aspx) there is an iframe which opens (mysite.com:8080/connector.htm)
the connector.htm starts a xmlhttprequest and when the server responses (Push) the data
will be written into the cookies, because the default.aspx on port 80 can't access to the iframe on port 8080 (browser restriction)
the script on default.aspx checks the cookies every 50ms for new data.
my community chat is working fine with that solution.