Edit 8/22/2019 IPs have been updated.
I’ve found 3rd party program that enables you to stay invisible and still use lol chat features and champion select chat contrary to the solution below. That’s why i recommend using this for as long as it works and is endorsed by Riot Games.
IP addresses marked with * might not work correctly
If your file doesnt work make sure its a bat file and not notepad file. Bat files should be detected as Windows Batch File, bat.
If command prompt appears but it doesnt work make sure your windows firewall is on. If it still doesn’t work run it as an admin.