Purpose     : Monitors an FTP server for incoming files
                  and processes them.

    Syntax      :

    Description : For the full FTP specification
                  look for RFC959 on http://www.faqs.org
                  This code should be considered as still in development, 
                  as such it has been unit tested only.
                  It was not written to be a generic solution.
                  It is heavily based upon the example smtp process
                  available from the Porgress Knowledge base.
                  Use this software at your own risk!
                  Jason Howells 12/07/2001

    Author(s)   : Jason Howells
    Created     : 04/06/2001
    Notes       : Some FTP terms are used throughout:
                  PI  = Protocol Interpreter
                  DTP = Data Transfer Process
                  
                  An FTP Session consists of the following components
                  
                  Client                Server
                  |                          |
                  PI -------Port 21---------PI
                  |                          |
                  |                          |
                  DTP-------Port xxx-------DTP
                  |                          |
                  
                  Theory
                  ------
                  Commands travel across port 21, data is transferred across an additional 
                  data transfer port.
                  Normally the FTP client process(this process) sets up
                  a server for the DTP and waits for the server process
                  to contact it.
                  There is however a slightly easier way that is also 
                  preferable when working through a firewall, Passive mode.
                  Passive mode revereses the process stated above.
                  When the client contacts the server process it issues
                  as PASV command to invoke passive mode.
                  The reply to the PASV command is a string that contains the
                  host and a port address for the DTP on the server.
                  In this way we only have to connect a client socket to the server.
                  This process is repeated for each file transfer.
                  The FTP specification states that control of the data connection
                  (DTP) resides wholly with the server process.
                  However during my testing I found it necessary to close the 
                  data connection from the client side before quiting the FTP session.
                  
                  Practice
                  --------
                  This program functions as follows:
                   1. Connects to the FTP server on port 21 and recieves a response.
                   2. Logs in using the gievn user name and password.
                   3. Sets the transfer type to I (to avoid CRLF's getting appended to
                      the end of every sodding line!)
                   4. Makes a list of all the xml files present.
                   5. Works through the list getting one file at a time and streaming it 
                      into a memory pointer.
                   6. This memory pointer is then passed to the Xload function that parses 
                      the XML document.
                   7. Once the document is parsed and loaded into the database, the remote file is
                      then moved into a different directory for archiving purposes.
                   8. The next file is then processed.
                   9. When the file list is empty, the program tries to retrive another list
                      if the response is '550 No such file or directory', then there are no xml files to 
                      retrieve so the process quits and control returns to the main block
                      in this procedure.
                  10. The program then pauses before beginning the cycle again.
                  
                  FTP Commands Used (RFC959 contains the full explanation)
                  Command Description
                  ------- ------------------------------------------------------------------------
                  USER    Specify username for login
                  PASS    Specify password for login
                  RNFR    Rename from... name of file to rename
                  RNTO    Rename to... new name of file
                  NOOP    Does nothing... returns OK, used here to trip the event processing
                  RETR    Retrieve... gets the named file
                  NLST    Name List... gets a simple list of files for the specifed directory.
                  QUIT    Go on guess...