Commands consist of a command word, which in some cases may be
   followed by a parameter.  Commands with parameters must separate the
   parameters from each other and from the command by one or more space
   or tab characters.  Command lines must be complete with all required
   parameters, and may not contain more than one command.

   Commands and command parameters are not case sensitive. That is, a
   command or parameter word may be upper case, lower case, or any
   mixture of upper and lower case.

   Each command line must be terminated by a CR-LF (Carriage Return -
   Line Feed) pair.

   Command lines shall not exceed 512 characters in length, counting all
   characters including spaces, separators, punctuation, and the
   trailing CR-LF (thus there are 510 characters maximum allowed for the
   command and its parameters).  There is no provision for continuation
   command lines.