Use the Toggle Passive (PASV) mode command to change from Active mode to Passive mode or Passive mode to Active mode.
The FTP protocol uses two ports, a control port and a data port.
In active mode the client initiates the connection to the server control port and the server initiates the connection to the client data port.
In passive mode (PASV) the client initiates the connection to both the control port and the data port.
command port : client to server
data port: server to client
command port: client to server
data port: client to server
The proper mode depends upon firewall and FTP servers settings. If active mode fails, try your connection in passive mode.