National Aeronautics and Space Administration

Wallops Flight Facility


The GFO File Transfer System (FTS) is designed to automate the handling of GFO CALVAL data. It is designed to operate autonomously with user intervention at a minimum

Contact Information


David Hancock

Jeff Lee


  • The FTS will “push” data to clients via an automated FTP.
  • The FTS will allow clients to “pull” data via FTP from an online repository.

File Naming Conventions

The FTS works only with all-lowercase filenames. The FTS automatically translates upper-case filenames to an all lower-case equivalent. The FTS uses a unique file-naming convention to determine what to do with files that are processed within the system. Each unique type of file used by a project must have a filename beginning with a unique 4-character code designated as “filetype”. This “filetype” code must be assigned to the filetype by the FTS administrator. Files without an appropriate filetype will cause an error condition within the FTS.

Incoming Files

A client may introduce a file into the system by transferring the file into the “inbox” (/in) via FTP. Criteria for submitting a file to the FTS via FTP are:

  • Files must be put in incoming directory (/in)
  • Filenames are case-sensitive and must conform to FTS file naming conventions.

The FTS checks each project inbox once per minute. If it sees a file in the inbox, it creates a lock file containing the current size in bytes of the file. The next time it checks the inbox, it compares the current size of the file with the size saved in the lock file. If the two match, the FTS assumes the file has completed transfer and moves the file. If the file sizes do not match, the new size is put into the lock file and the process repeats. Do not be alarmed if files disappear out of the inbox; the FTS is just doing its job.

Outgoing Files

There are two basic methods by which files may be sent to clients. A file may be automatically “pushed” via FTP or it may be put in the “outbox” (/out) for “pull” retrieval. The FTP “push” mechanism is somewhat persistent. It can discern whether a file has been transferred correctly and will keep trying for up to three times if the transfer is not successful. After a third unsuccessful try, the FTS will send email to the FTS operator informing him of an error condition. The FTS will keep a two-week (TBD?) repository of data for the GFO CALVAL project. In order to ease client “pulls”, the FTS will, on a daily basis, create a text file listing new files which are entered into the repository. The text file will be named in the format:



The FTS is built upon rooted FTP directories. Clients will not have access to the remainder of the file system.

  • Clients will be allowed FTP-only access to the server. Telnet services will not be permitted.
  • Passwords will be provided to each client. Password changes will be handled locally to insure good password selection and password change compliance. Multiple clients may be assigned the same userid and password, if deemed appropriate by the FTS administrators.
  • Clients must supply the FTS administrator with the hostnames and IP addresses of machines which need access to the FTS before attempting their first connection.


All actions performed by this system are logged in a log directory. The administrator can check this logfile if problems occur.