Passive or Active: Picking FileZilla's Data-Channel Mode for a NAT-Blocked Production Server
FTP splits every session into a control channel (default port 21) and a separate data channel for listings and transfers, and the data channel is the common failure point when a FileZilla setup moves from a LAN to production. Passive mode, FileZilla's default, has the client connect out to a server-supplied address and port; active mode has the server connec