stop showing 0.0.0.0

[davidism]

Not sure how feasible this is, but it's one of the more common questions I see on SO. Users for whatever reason run the dev server on 0.0.0.0, see Running on http://0.0.0.0, then are confused when they can't get to that IP in most browsers or scripts. Maybe if Werkzeug sees that value, it displays a more helpful message with the real ip (or localhost if not possible) and a warning about running the dev server in production. Running on all interfaces (try http://{real ip}). Warning: Don't use the development server in production.

[jab]

Great idea @davidism, I've seen users hit this too, and was impressed when I tried npx @11ty/eleventy --serve for the first time and saw the Browsersync output included my (LAN) external IP, in case that's helpful prior art:

Watching…
[Browsersync] Access URLs:
 -------------------------------------
       Local: http://localhost:8080
    External: http://192.168.0.11:8080
 -------------------------------------
          UI: http://localhost:3001
 UI External: http://localhost:3001
 -------------------------------------
[Browsersync] Serving files from: _site

Something like this would get us that much (based on https://stackoverflow.com/a/28950776):

with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as s:
    try:
        s.connect(('10.255.255.255', 1))  # need not be reachable
        return s.getsockname()[0]
    except Exception:
        return '127.0.0.1'

Not sure it's in scope, but if we wanted to try to get the host's WAN IP, I think we'd either have to try querying the router over UPnP, which requires a UPnP client, as in https://stackoverflow.com/a/41385033:

import miniupnpc
client = miniupnpc.UPnP()
client.discoverdelay = 200
client.discover()
client.selectigd()
return client.externalipaddress()

...or resort to querying some public "what is my IP" service (https://ident.me, http://canhazip.com, etc.) as in https://stackoverflow.com/a/41432835.

[akshgpt7]

I'll be working on this.