ERR_ADDRESS_UNREACHABLE on macOS with browsers

Over the last few versions of macOS upgrades, the app-based egress control has been strengthened. The result is that non-Safari browsers will trigger a prompt like this:

local-network-prompt

If “Don’t Allow” is selected, it makes MyTools inaccessible as it is your local network that is serving up your MyTools service. You will receive an error message of:

ERR_ADDRESS_UNREACHABLE

The solution

To fix this, navigate to the Apple Menu → System Settings → Privacy & Security → Local Network and enable your browser’s access like this: