TEXT denotes that literally this text is sent or received. The newline character is normally not allowed in those items. Upon startup, the client will connect via TCP to the mudFTP port. This will typically be the port of the main MUD, plus 6. Typical implementation would use the character's password, requiring the character to be online while connection happens.
Additional information can contain whatever the server pleases.
It may be in the future used as some sort of capability string. The server should not inform whether the failure was because of a user that does not exist or an invalid password. The GET command is used to retrieve a remote file. With the client in push mode, the filename comes from the MUD client that invoked mudFTP, which in turn comes from the MUD server. The filename identifies the particular string being edited.