Important Notice: Our web hosting provider recently started charging us for additional visits, which was unexpected. In response, we're seeking donations. Depending on the situation, we may explore different monetization options for our Community and Expert Contributors. It's crucial to provide more returns for their expertise and offer more Expert Validated Answers or AI Validated Answers. Learn more about our hosting issue here.

What are FTP passive connections?

April 26, 2017FTP passive

0

Posted

What are FTP passive connections?

2 Answers

0

Posted

by Colin Campbell Ftp uses two data streams, one for passing commands around, the other for moving data. The command channel is handled by the ftpd listening on port 21. The data channel varies depending on whether you ask for passive ftp or not. When you request data in a non-passive environment, you client tells the server “I am listening on .” The server then connects FROM port 20 to the ip address and port specified by your client. This requires your “security device” to permit any host outside from port 20 to any host inside on any port > 1023. Somewhat of a hole. In passive mode, when you request a data transfer, the server tells the client “I am listening on .” Your client then connects to the server on that IP and port and data flows.

0

10 Posted

by Colin Campbell Ftp uses two data streams, one for passing commands around, the other for moving data. The command channel is handled by the ftpd listening on port 21. The data channel varies depending on whether you ask for passive ftp or not. When you request data in a non-passive environment, you client tells the server “I am listening on .” The server then connects FROM port 20 to the ip address and port specified by your client. This requires your “security device” to permit any host outside from port 20 to any host inside on any port > 1023. Somewhat of a hole. In passive mode, when you request a data transfer, the server tells the client “I am listening on .” Your client then connects to the server on that IP and port and data flows.