Friends Can't Connect To Modpack Server

[CloroxBleach]

So I have an error with my server for a modpack. I have all the mods installed on the server correctly, weeded out the client side mods, and done everything right. I can connect to my server easily but friends from a different router can't. I have tried almost every method I have seen. I have port forwarded my IPV4 address with ports TCP and UDP 25565. I have added port rules on firewall for 25565. I have allowed Java SE Binary, javaw.exe and minecraft through firewall. I know a lot of people said to keep server.properties blank, but the minecraft says you can have it set to whatever you want for an IP that everyone connects to. I've tried putting my external ip in the ip address, i've tried it with nothing there, i've tried port forwarding my external Ip, i've tried near everything I could think of and find on any forum sites. Yet, my friends still gets the Connection Timed Out error. Anybody know a fix? Is it a problem on my friend's side? Please help.