What Are Active and Passive Mode?
FTP protocol uses two connections; one for commands and responses, another for data. When you give your FTP client a data transfer command such as GET or PUT, a second port is opened for the data. The server’s command (control) port is normally 21 and its data port is normally 20. The client, however, can use any random port numbers greater than 1024 for its end of each connection: • In Active Mode, the client tells the server its data port number and then waits for the server to open a data connection to that port. • In Passive Mode, the client tells the server to enter Passive Mode with a PASV command; the server responds with its port number and waits for a connection from the client on that port. Passive is Kermit’s default mode since it tends to work better with firewalls. This is because the choice of port numbers is controlled inside the server-side firewall, and thus the server and the firewall can be configured by the site’s network and system administrators to accommodate eac
