On most networks port 80 is reserved for HTTP. But if the server is listening at port 8080, you will always have to specify 8080.
At the logon screen for STS you will see the username, password and port. Port is set to 80 by default, but can be toggled to choose 8080. This might not always remedy your issue, but it's worth the try. Some public networks might have a firewall that will never let you connect to our servers. Time to try the hot spot. :)