TheFTP protocol is unusual in that two TCP/IP connections between theclient and server are required to transmit files. Commands and responsesbetween the client and server are exchanged across the control connection.Data transfers including directory listings are conducted on oneor more distinct data connections. On FTP gateway a new data connectionis opened each time a transfer is necessary.

The FTP gateway supports both active and passive FTP modes. Noprior setup is necessary to change from one mode to the other. Howevercontact Customer Support to determine if your mailbox supports bothactive and passive modes.

In active FTP mode which is the default for most FTP clientsthe client initiates the control connection and the server initiatesall data connections. However some firewalls reject connection attemptsfrom Sterling B2B CollaborationNetworkwhich prevents data connections from being built. When this happensFTP sessions time out after several minutes of inactivity and youreceive no information as to why the session failed.

Customers who consistently experience FTP time-outs when performing ls dir get mget putor mput commands can often correct the problemby switching to passive FTP mode. In this mode the FTP client initiatesall the data connections. Because firewalls usually allow all outboundconnections the problem with establishing data connections is corrected.

If passive FTP mode might be useful for your connection to Sterling B2B CollaborationNetworksee your FTP client documentation to determine whether it is supportedand how it can be enabled. Passive FTP can also be used with Event-drivenFTP. Contact Customer Support to have passive FTP mode enabled onan Event-driven mailslot.