Most of the time it doesn’t make a difference what you use, “localhost” or 127.0.0.1. It turns out that it does make a somehow big difference when connecting to a mysql server.
If you use “localhost” most clients will try to “connect” via the socket file that the server puts, if it adheres to the standard, into /tmp, if you use 127.0.0.1 a IP connection is made.
I was made aware of this fact when I tried to connect to the mysql server that comes with XAMP. Its configuration does not adhere to the standard and puts the socket file into /Applications/XAMPP/xamppfiles/var/mysql/mysql.sock on OSX.
The clients that wasn’t aware of this fact obviously failed to connect and threw the error: “Connect Error: SQLSTATE[HY000]  No such file or directory” when a connection attempt was made. Hope who ever has the same problem finds this and spends less time debugging then I did 🙂