Page History

When the client wants to use a passive data connection, the server should provide the port to use. By default, FTPServer FtpServer will choose any available port. However this can be overridden using the configuration parameter config.listeners.default.data-connection.passive.ports (if using the default Listener. for the passive data connection. The allowed passive ports can then be specified as a single port (e.g. 20020), multiple ports (e.g. 20020, 20030, 20040) or a range of ports (e.g. 20020-20030). Ranges can be closed (e.g. 20020-20030) or open ended (e.g. 60000-). Open ended ranges start at 1 and end at 65535, that is, the range 60000- will allow all ports between 60000 and 65535. Any combination of specified values or ranges can be used.

When the server has used up all passive ports (one per client doing passive data transfer), the next clients will have to wait for an available port. It is therefore adviced advised to provide multiple passive ports.

...