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What is FTP passive mode?

Applied Models:

  • ICS-1013
  • NVR-101
  • NVR-1012
  • NVR-104P
  • NVR-104V
  • VioCard-100
  • VioCard-300
  • VioGate Master
  • VioGate-140
  • VioGate-340(340A)
  • Vioserver-10
  • Vioserver-5
  • VioStor-101A
  • VioStor-101P
  • VioStor-101V
  • VioStor-2008
  • VioStor-2012
  • VioStor-201A
  • VioStor-201P
  • VioStor-201V
  • VioStor-5012
  • VioStor-5020
  • VioStor-8040
  • VioStor-8040U-RP

Answer:

FTP supports two modes, Standard (or PORT or Active) and Passive (or PASV).
Compared with the Standard mode, the FTP clients of the Passive mode also start by establishing a connection to TCP port 21 on the FTP server to create the control channel. When the client sends a PASV command over the command channel, the FTP server opens an ephemeral port (between 1024 and 5000) and informs the FTP client to connect to that port before requesting data transfer. As in Standard mode, the FTP client must send a new PASV command prior to each new transfer, and the FTP server will await a connection at a new port for each transfer.

2009/06/22
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