I can't connect to my server when not on my home network

As I write this, my friend is connected to my home server from several states away.

I cannot connect to my server. I've input the exact same IP and port number as my friend, which I've checked and is still the correct IP and port number on the host computer.

I can successfully join when on my home network (which the server is hosted on) by giving the local IP of that PC.

When I try to login from not-home, I get:

Failed to connect to the server

io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection timed out:

no further information:

Any ideas on how to resolve this?