FTP, Firewall

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FTP, Firewall

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Note that none of these settings are available when using SFTP as they are not applicable.


Passive: If you are behind a firewall then you may need to enable this option. If SyncBack can login to the FTP server, but cannot transfer files or retrieve a folder listing, then try enabling this option to see if it fixes the problem. Passive FTP connections mean that the FTP client (SyncBack) connects to a TCP/IP port opened on the server when transferring data. Active connections (i.e. not passive) mean that the FTP server connects to a TCP/IP port opened on computer running the FTP client (SyncBack) when transferring data. So with an active connection you need to configure your firewall to allow inbound connections. The settings below relate to that.


Try to keep the connection alive during file transfers: It is not recommended that this option is used. Use of this option with many FTP servers can cause odd errors (because the commands sent to the FTP server, and the replies given by it, can become "out of sync"). If this option is enabled then when files are sent to, or received from the FTP server, a NOOP command is sent to the FTP server every 30 seconds. In some rare cases this can stop the FTP server from assuming the connection has been broken during long file transfers. However, in the majority of cases the use of this option instead causes more problems.


Use Clear Command Channel (CCC): Choose this option if you are behind a firewall or router that uses NAT (Network Address Translation) and you are having connection problems. Some routers can dynamically change the FTP communication to translate I.P. addresses but this can only be done if that part of the FTP communication is not encrypted. This setting is only used with encrypted connections.


For passive connections, always use the servers IP address: This option is only available with passive connections. By default, the IP address returned in the PASV reply is used to communication with the server. However, if this option is enabled the IP address of the connection is used. This is useful when the FTP server has not been configured correctly for passive connections and is returning it's LAN IP address instead of it's Internet (External) IP address.


Port mode for active connection: This option is only used with active (not passive) connections (see above). If you are behind a router, and are using NAT (Network Address Translation), then you may need to specify your external I.P. address. There are three choices: default, manual and automatic. Default means the I.P. address of your computer is used. This is very likely to be wrong, but it is possible your router will try to automatically fix this. Manual means you specify the I.P. address to use (see the External I.P. address setting below). Automatic means it will try and determine what your external I.P. address is by querying your router (if it's UPnP enabled), and if that fails it will use an external web site to retrieve it. This setting is not available with all FTP engines.


External I.P. address: This option is only enabled if it is an active (not passive) connection and the port mode is set to manual. This is usually the I.P. address of your router and is not a local I.P. address. Variables can be used. Also, it is not available with all FTP engines.


Use ports ranging from...: If you are behind a firewall then this is the range of TCP ports that you must open on your firewall to allow the FTP server to contact SyncBack. If the ports are not open then files cannot be transferred and directory listings will fail. This option is only used with active connections (because with a passive connection the FTP server must be configured to specify which ports it tells the FTP client, SyncBack, to use). Also, it is not available with all FTP engines.



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