I tried the online proxy suggested by giqcass, replacing "type.your.ip.here:80" with the ip I find when I query "what's my ip", with :80 after it.
I believe that this is the IP address of my cable modem, which gives it to my router, which is how my entire home network (not any one PC) is represented to the outside world.
I got the following message back:
request to url [
http://xx.xx.xxx.xx:80] fail, reason - couldn't connect to host
Again, I believe that a scan using Shields Up at
www.grc.com, which reveals that I'm "Stealth" on everything, shows that nothing can get it because nothing can be found. However, I'm not a network expert, so please show me where I'm not understanding.