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HTTP Proxy Forces FTP Voyager to PASV mode  -  KB Article #1609

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Because of the nature of HTTP proxy servers, FTP Voyager can only connect through them using passive (PASV) mode. If the site profile is configured for active (PORT) FTP mode, FTP Voyager will leave that setting intact, but will use PASV mode to connect through the HTTP proxy.

This behavior is because the HTTP proxy protocol does not allow for incoming connections. Because initiating a PORT command causes the server to create an incoming connection, it is not possible to connect using PORT FTP over an HTTP proxy, forcing FTP Voyager to strictly use PASV mode, an outgoing connection, for the data socket. When connecting through an HTTP proxy server, the "CONNECT" command is used instead of the "GET" or "POST" HTTP commands, thus allowing only outbound connections.

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