My friend created a server using a docker image for skyfactory 4. 

https://hub.docker.com/r/filoozom/skyfactory4

When I try to join the server it gives me the error "this server has mods that require fml/forge to be installed on the client"  I have forge installed on the client with the correct version being launched.  I also have the mods in the mod folder that I pulled from the docker page he is using for the image.  

Attached is my logs

debug.log

Skyfactory 4 is 1.12.2, which is no longer supported on these forums.

 

You will not be able to connect to that server using modern and supported versions of forge. (i.e. using the 1.15.2 version you have, which is supported, will not work with that old version, but downgrading to an old version to try and get on there means you cannot get help here if you have problems.)

 

That does not mean that you CAN'T use it/play on it, just that you will have to look elsewhere for help.

 

More information on supported versions can be found in the LTS link at the top of every page.

I have read through the history of posts similar to these on the site and sent the logs from 1.15.2 since 1.12 isn't supported.  I get the same error either way and the connection logs from the server are attached.  I have the exact same mods in the folder and forge is installed and shows as connecting.  

message.txt

You won't be able to connect to Skyfactory 4 using 1.15.2, simple as that.