[FTP] PORT vs. PASV
Ein schönes Zitat möchte ich hier heute mal zum Besten geben, das unterhaltsam (speziell PASV) den Unterschied zwischen Aktiv- und Passivmodus bei FTP verdeutlicht (danke an Sebi!):
PORT (Active) Mode:
CuteFTP takes a very aggressive, active role in establishing the data channel connection. Over the command channel via port 21 it squares its shoulders, looks the remote server in the eye, and tells the server, “Connect back to me on my IP address and my port!” The remote server obeys and makes an outbound connection to CuteFTP at the IP address and port specified by CuteFTP. Once that data channel is established, the data transfer takes place.PASV (Passive) Mode:
CuteFTP takes a very passive role in establishing the data channel connection. It meekly sends four letters: PASV. It’s basically lowering its eyes and saying, “Server, you tell me what you want me to do, and I’ll obey.” So the remote server replies, “OK, cool. You connect to me at my address and my port.” CuteFTP then dutifully obeys and creates a new outbound connection to the server at the IP address and random port specified by the remote server. Once that data channel is established, the data transfer takes place. PASV mode is necessary for some firewalls and routers, because with PASV CuteFTP opens the connection to an IP Address and port that the server supplies.
via globalscape