Obtaining the name of the host in environment.rb

Hi,
For testing purposes, we deploy our app on different PCs. In the
environment.rb file , we would like to set a constant to the name and
port of the host. Is there a function that we can call to obtain the
host and port when called from environment.rb?
Ideally we want something like
SVR=host_and_port()

Remember, we cannot use ActionController#host_with_port because we are
not in an action.

Thanks,
Yash