FTP server’s port 20 from ports > 1024 (Client sends ACKs to server’s data port).FTP server’s port 20 to ports > 1024 (Server initiates data connection to client’s data port).FTP server’s port 21 to ports > 1024 (Server responds to client’s control port).FTP server’s port 21 from anywhere (Client initiates connection).Client’s port > 1024 from the server address (Server connects to the client’s data port to transfer a file).įrom the server’s perspective the following communication channels need to be allowed in its own firewall in order to support active mode FTP:.Allow the connections to the port 21 of the server address (Client initiates connection).The file’s data will then be transferred using this connection.įrom the client’s perspective the following communication channels need to be allowed in its own firewall in order to support active mode FTP: The server will then connect back to this data port of the client using its own local data port, which is port 20. In Active mode (also called non passive) the client starts listening on port N+1 and sends the FTP command PORT N+1 to the FTP server. The purpose of the SETPASSIVE command is to select the method that ScriptFTP will use. There are two methods for opening these new data channels: Active and Passive. For file transfers this connection will not be used, rather a new connection will be established for each file in order to transport the file’s data. Once the connection has been established the client will authenticate to the server and then this connection is the one client and server will use to ‘chat’ with each other. You may change your FTP server configuration such that it listens on a different port, however, port 21 is the standard. When connecting to an FTP server the client usually opens port 21 on the server where the server is listening and waiting for incoming connections. SFTP protocol works in a completely different way to transfer file data. This command only works with FTP and FTPS protocols as “passive mode” is a concept related to these protocols only. Switching the transfer mode and/or configuring your firewall may help. Should you experience firewall problems please read this section carefully. This mode is called Active in the FTP standard. SETPASSIVE Enable or disable FTP passive transfer modeĭisable passive transfer mode.
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