Date: Tue, 14 Oct 1997 22:51:38 +0100 From: Martijn Koster <mak@webcrawler.com> To: Doug White <dwhite@resnet.uoregon.edu> Cc: Wei Weng <wweng@stevens-tech.edu>, freebsd-questions <freebsd-questions@FreeBSD.ORG> Subject: Re: install port collection Message-ID: <19971014225138.48057@webcrawler.com> In-Reply-To: <Pine.BSF.3.96.971014142243.2718C-100000@gdi.uoregon.edu>; from Doug White on Tue, Oct 14, 1997 at 02:24:33PM -0700 References: <Pine.SGI.3.96.971014124441.16819A-100000@attila.stevens-tech.edu> <Pine.BSF.3.96.971014142243.2718C-100000@gdi.uoregon.edu>
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On Tue, Oct 14, 1997 at 02:24:33PM -0700, Doug White wrote: > On Tue, 14 Oct 1997, Wei Weng wrote: > > > Thanks for your replying. But what is passive FTP mode? How can I know if > > I am using it or not? > > I don't know how pssive FTP works, but it connects in a different fashion > that doesn't upset firewalls as much. With a normal connection, the client opens a command channel to the FTP server, creates a local port, then asks the server to open a connection back to the local port, to actually transfer the data. The second connection is the bit firewalls don't like, because it is backwards from outside in. With passive FTP, the client command channel to the FTP server, asks _it_ to create a port and tell the client what it is, so the client can then connect to it. Because both connections go forward from inside to out, the firewall is OK about it. For more details see the "Building Internet Firewalls" O'Reilly book, or of course the RFC. -- Martijn Koster, m.koster@pobox.com
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