If you have a firewalled client and a firewalled server, without special FTP support in the firewalls, you can't do FTP between those machines, neither PASV nor PORT will work. Same thing for PASV on a firewalled server. To get PORT to work on a firewalled client, the firewall has to be aware of the FTP protocol, as it has to re-write the control commands to correct the addresses, and forward the appropriate inbound connections. PASV won't work if the SERVER is behind a firewall which forwards the control connection (port 21) through. It's called passive because the server just sits there and waits, it doesn't initiate the connection like "classic" FTP's PORT command. Instead of issuing the PORT command, the client issues the PASV command the server's response tells the client the IP and port to use. Passive mode means the SERVER opens a second listening port, just for that one client, and the client opens a second outbound connection to it. If you are behind a masquerading or NAT-ing firewall ("internet sharing router"), the PORT command will have the IP address from the internal network, which hopefully isn't routable. If you use the old command-line FTP program, you'll have seen messages like "PORT command successful"-PORT is the command that tells the server the IP and port to contact (i.e., where on the local machine). Normally, the FTP client opens a listening port on the client machine ("inbound" port, server port) and tells the server about it. A long-running control connection (usually to port 21 on the server) and a per-file data connection. OS X provides read-only FTP access in Finder, you can press Command-K in a Finder window and enter the FTP URL (something like ), and connect to FTP Server. The control port isn't usually a big deal, unless the nonstandard port is blocked on the client's firewall.įTP works on two TCP connections. FTP Server lets you run the FTP service on your own computer and you can access the files on the host computer with any standard FTP client such as FileZilla or WinSCP.
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