"Unable to establish connection" - Multi-Player server

[Doctorjack123]

I made a server with my friend and when I went of to have dinner i closed of the game.
Then when I came back and turned on Factorio and loaded the save for the first time my friend got a error when trying to connect "Couldn't establish network communication with server".
I tried to 'Re-port forward' the server but nothing changed.
I was wondering why it only happen'd the first time I loaded the world as it worked fine when I;
1. Made a port forward for the game
2. Clicked "Play" "Multi-player" "New World" "made world"
3. Sent friend my IP :port
4. Played Factorio
5. Saved the world
6. Came back on and clicked "Play" "multi-player" "Load World" "Selected world" "Joined the world"
7. My friend tried the IP :Port and the IP only.
I have no idea why I didn't work and I also tried to make a brand new port forward, and world but it was the same thing.
We are both using the same version and we have the same mods turned on and off.