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000399_fdc@columbia.edu_Tue Apr 1 11:16:09 EST 2003.msg
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Article: 14201 of comp.protocols.kermit.misc
Path: newsmaster.cc.columbia.edu!news.columbia.edu!news-not-for-mail
From: fdc@columbia.edu (Frank da Cruz)
Newsgroups: comp.protocols.kermit.misc
Subject: Re: No route to host
Date: 1 Apr 2003 11:15:49 -0500
Organization: Columbia University
Lines: 28
Message-ID: <b6cdvl$noi$1@watsol.cc.columbia.edu>
References: <Pine.A41.4.44.0303312301330.100834-100000@public.uni-hamburg.de> <b6abl2$k62$1@watsol.cc.columbia.edu> <Pine.A41.4.44.0304010942290.96622-100000@public.uni-hamburg.de>
NNTP-Posting-Host: watsol.cc.columbia.edu
X-Trace: newsmaster.cc.columbia.edu 1049213750 27078 128.59.39.139 (1 Apr 2003 16:15:50 GMT)
X-Complaints-To: postmaster@columbia.edu
NNTP-Posting-Date: 1 Apr 2003 16:15:50 GMT
Xref: newsmaster.cc.columbia.edu comp.protocols.kermit.misc:14201
In article <Pine.A41.4.44.0304010942290.96622-100000@public.uni-hamburg.de>,
Menge, Oliver <Oliver.Menge@web.de> wrote:
: On 31 Mar 2003, Frank da Cruz wrote:
: > Try making an active, rather than passive, connection:
: >
: > ftp open www.joe-list.de /active
: >
: > and see if that makes a difference.
:
: Thanks a lot. That makes a difference. Transfer works fine now! Can you
: give me hint, where to learn more about the differences between
: active/passive ftp?
:
It's almost futile to try to explain it these days when the Internet is so
complicated and unstable: firewalls, nats, proxies, host pools, blah blah
blah. It all boils down to "if A doesn't work, try B".
Briefly, FTP makes two connections: a control connection (for commands)
and a data connection (for files). This worked fine for decades, but now
it runs up against firewalls, etc. Active and Passive mode determine
which side, the server or the client, creates the data connection. On
some connections one works, but not the other.
For details see:
http://www.columbia.edu/kermit/security.html#x2.1.1
- Frank