Cannot connect to KO server. (-1)

[stucks]

whenever my friend want to connect to my server, they got the error.
anyone know whats the problem might be?

 

[BlaDe2qj]

Do they get to server select or no?

Sounds like a port forwarding issue.

 

[ZeroTears]

Im getting the same problem, when i select my server and press connect i get that error

"Failed connecting to "the server" error (-1)"

 

[gayacorp2004]

have you solve ?