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No StarNo StarNo StarNo StarNo Star | Apr 23 2012, 6:58 PM |
FTP session cannot connect
A client connection to a server for the purposes of FTP (File Transfer Protocol) communication is sometimes configured in 'Active' mode. 

When establishing an FTP connection using a client that is operating across Sharedband however, 'Active' FTP cannot be utilised due to the incompatibility explained:


If an Active FTP session is initiated by the client connecting to a port that has been opened to the server. It then commands the server to respond using a different port which it subsequently listens on. The server attempts to make this return connection but is unable to do so due to NAT (Network Address Translation) characteristics of the Sharedband service.

To avoid this incompatibility Passive FTP will need to be employed instead.

Passive FTP is again initiated to the server by the client connecting to a port that has been opened to the server. In passive mode however, the client queries the server for a port to begin data transmission to. The server allocates and begins listening to this port before replying to the client with the port number. Equipped with the authorised port number, the client is able to successfully transmit data to the server.


Passive FTP is a feature of many popular FTP clients. The Windows FTP command however does not support this feature (although there are many forum posts online that suggest otherwise)

There are a few (free) alternatives ...

If communication still cannot be achieved after Passive FTP has correctly been configured, please check with the FTP server host whether inbound packet blocking has been applied (as is a default setting for some virtual machine environments) as if it has, it will likely be stopping FTP communication.


Finally, if the FTP server is provided by Mircrosoft IIS 7, either IIS 7 or the Windows firewall may not have been configured correctly for Passive FTP mode. For guidance on correcting this, please review: and