How does this command work?
ionic serve --all
Can I access the application from a browser on another machine in my LAN, or anywhere on the web?
The command ionic serve creates a NodeJS server on your machine. This means that it may be accessible from anywhere if you configure well your router.
However, where have you seen that parameter --all
I see only the following
serve [options] ........................... Start a local development server for app dev/testing
[--consolelogs|-c] ................. Print app console logs to Ionic CLI
[--serverlogs|-s] .................. Print dev server logs to Ionic CLI
[--port|-p] ........................ Dev server HTTP port (8100 default)
[--livereload-port|-r] ............. Live Reload port (35729 default)
[--nobrowser|-b] ................... Disable launching a browser
[--nolivereload|-d] ................ Do not start live reload
[--noproxy|-x] ..................... Do not add proxies
[--address] ........................ Use specific address or return with failure
[--browser|-w] ..................... Specifies the browser to use (safari, firefox, chrome)
[--browseroption|-o] ............... Specifies a path to open to (/#/tab/dash)
[--lab|-l] ......................... Test your apps on multiple screen sizes and platform types