FTP CONNECTION PROBLEMS
Some users have reported problems when downloading files from our web site using FTP. In a few isolated cases this is because the user's IP address has been inadvertently blocked by NASA's spam filtering software. If this is the case you will not get any response at all from the HEASARC ftp server. More typically, however, the user will see a login message, and then a message similar to "Service not available, remote server has closed connection". We are not exactly sure of the cause of this problem, but it appears to occur only when the user's machine is located behind a firewall which has not been set up properly to allow FTP access. FTP data transfer does not come back on the same port that the original connection is made on, so unless the firewall is configured to recognize the FTP replies, it will think that it is a new connection and will block it. Stateful firewalls see outgoing connections and can keep track of replies. If you have this problem, you need to talk to your system administrator about changing the configuration for your firewall or FTP software. Fortunately, HTTP connections do not have this problem, so as a work around users can download our files using HTTP rather than FTP. To do this, note the FTP address that is causing the problem, and then modify the address by substituting "http://" instead of "ftp://", and inserting the string "/FTP" after the ".gov" in our machine address. For example, the following FTP address ftp://legacy.gsfc.nasa.gov/fits_info/sample_files/events/ should be changed to: http://legacy.gsfc.nasa.gov/FTP/fits_info/sample_files/events/ Enter this http address in your web browser to download the file.
Help lines: FTOOLS or email@example.com
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Last modified: Tuesday, 09-Oct-2001 18:52:03 EDT