FTP Error Codes Explained

The FTP errors suck. Not knowing the meaning of the error code can avoid a user from troubleshooting the issue. Here is a useful reference list that i found dumped inside the deepest region of my HD:

Code Description

100 Codes The requested action is being taken. Expect a reply before proceeding with a new command.
110 Restart marker reply.
120 Service ready in (n) minutes.
125 Data connection