Hah!  That's a lot harder question than it first appears.  :)

Anyway, I was curious, because I had never heard of the TcpServerChannel  
object in the first place.  I assumed that it'd have some sort of EndPoint  
property that would return the assigned address.  But alas, that wasn't  
the case.

This is a wild guess -- I don't have any code that uses a TcpServerChannel  
so I can't really test this theory -- but reading the docs it looks to me  
like this might work (C#):

    int PortFromChannel(TcpServerChannel channel)
    {
        ChannelDataStore store = (ChannelDataStore)channel.ChannelData;

        return store["port"];
    }

Pete