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Old 06-07-2003, 02:45 PM   #1
billycert
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Default How is FXP working in details?

Hi, All;

I am a newbie here. I read FAQ and help on flashFXP site, neither clearly stated how FXP is working in details.

After I connect to both FTP site, when I started FXP between sites, a data channel initiated between these sites? Who initiats the data channel between them by default? Will it works if my flashFXP connects to one site via active ftp and another site via passive ftp?

What is the deferent behavior between the default and the "Alternatice FXP method" What does the "downloading(no pasv)" or "uploading(pasv)" switch change the benavior of both ftp server or the flashfxp client?

If both ftp servers are behind of firewall, what port needs to be open for fxp? What about NAT, will it work?

Please help me or point me to a direction where I can find the answer.

I kept getting
"Transfer Failed!
1 File failed to transfer
Server Error, Aborted"

Thanks

billy
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Old 06-07-2003, 03:15 PM   #2
MxxCon
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check out http://slacksite.com/other/ftp.html 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 http://forum.flashfxp.com/showthread...&threadid=3078
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Old 06-08-2003, 08:33 AM   #3
billycert
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Thank you MxxCon for replying!

I understand how FTP works. All I said was I could not find a good defination about how FXP works.

You mentioned "in order for FXP transfer to work one server MUST support passive connection and other MUST support "active" connection." Does it matter which one is active and which one is passive?

Also you mentioned "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)."

If I interpret "forword control and data port" as static nat, is that correct?

Thank you!

billy
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Old 06-08-2003, 08:58 AM   #4
billycert
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I did a test and found this:

Transfer file from Site A to Site B, both FTP server are serv-U and set to support FXP.

I connected to Site A using passive, Site B using active. When I pull file from A to B, FlashFXP by default sent a "PORT" command to site B. Site B received "Port" command to connect to site A, it simply use the same data channel to connect to Site A, which at the same time droped the data channel to FlashFXP. Any idea how to fix this?

Thank you in advance!

billy
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Old 06-08-2003, 03:02 PM   #5
MxxCon
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Quote:
Originally posted by billycert
Does it matter which one is active and which one is passive?
if both servers have properly configured port forwarding/firewall rules then it doesn't matter. if one is behind router/nat then that server should be in PORT mode, and open server should be in PASV mode.
Quote:
If I interpret "forword control and data port" as static nat, is that correct?
i'm not exactly sure what you mean by "static nat".
"forword control and data port" means firewall/router should have control connection port (21) and data connection port range (5000-6000) forward packets to the machine that's running server.
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