File eXchange protocol definition
File eXchange protocol (FXP) is a way to transfer data from one remote FTP server to another without passing through the client's connection. Unlike standard FTP (File transfer protocol), where files travel between a client (local) and a server (remote), FXP enables direct server-to-server file transfers while using FTP infrastructure.
See also: FTP proxy, passive file transfer protocol, secure file transfer protocol, trivial file transfer protocol
How the File eXchange protocol works
FXP works by using the FTP protocol's command set to coordinate a connection between two servers. The client initiates the transfer by telling the source server to connect to the target server and then commands the source server to transfer files directly to the target server. This process is handled by FTP commands like PASV (passive) and PORT, which set up the necessary data connections between the servers.
Security concerns
FXP can expose servers to unauthorized access. For FXP to work, both FTP servers must support and enable FXP, and often, servers need to disable certain security checks, making them vulnerable to FTP bounce attacks, among others. Because of these security concerns, many FTP servers disable FXP by default.
