in reply to Re: problem with put function
in thread problem with put function
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FTP Connections and Firewalls
by ikegami (Pope) on Oct 14, 2004 at 15:37 UTC
Say SERVER is 22.214.171.124.
In active (PORT) mode, the dialog for a file transfer looks something like this:
Firewalls which are not specifically aware of FTP don't know that the incoming (data) connection shouldn't be blocked, and NAT routers which not are not specifically aware of FTP don't know to which machine to forward the incoming (data) connection.
In passive (PASV) mode, the dialog for a file transfer looks something like this:
In this scenerio, the client doesn't need to accept any incoming connection. Many FTP clients now default to passive mode due to the popularity of NAT for home machines.
FTP's multiple connections has been very troublesome to people configuring firewalls and requires firewalls to be aware of FTP specifically (while they don't need to know about anything HTTP, for example). If you have trouble getting a directory listing from a FTP server after supplying your user name and your password, it's probably because of firewall/NAT issues, since directory listings treated like a file transfer. Try switching between active and passive mode.