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Old 06-07-2003, 03:15 PM  
Super Duper
Join Date: Oct 2001
Location: Brooklyn, NY
Posts: 3,876

check out for explanation of ftp protocol. once you understand that, you'll understand how fxp works.

in order for FXP transfer to work one server MUST support passive connection and other MUST support "active" connection.
you send PASV command to one server, that server will reply with ip and port it will await connection at.
you send PORT command to the other server with ip and port that the server above specified.
"Alternative FXP" switches those commands around, PASV become PORT and PORT become PASV. this is usefull when some sites are misconfigured, behind firewall/nat or are configured not to connect to ip other than the ones user used to connect with.

if both ftp servers are behind firewall or nat, FXP transfer will not work unless, at least one server will forward it's control connection port (often it's port 21), and it's data connection port range(must be above 1025).

error message you posted is not enough to troubleshoot your problem. read post RULES for this forum
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