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  1. Commons Net
  2. NET-363

Can't connect to a server behind firewall in passive mode

    Details

    • Type: Bug
    • Status: Closed
    • Priority: Blocker
    • Resolution: Fixed
    • Affects Version/s: 2.2
    • Fix Version/s: 3.0
    • Component/s: FTP
    • Labels:
      None
    • Environment:

      Windows Client with Zos mainframe server behind a firewall. However I think any client/server will demonstrate the issue as long as the server is behind a firewall.

      Description

      When the FTP server is behind a firewall, FTPClient can connect, but it cannot transfer data. This is because the FTP server provides it's own address instead of the firewall address to make the connection. I have confirmed the problem by hacking a copy of FTPClient to set the __passiveHost to the appropriate internet address. With this hack, I can transfer data.

      Perhaps the FTP server could be configured differently to fix the issue. Unfortunately, I do not have access to the server configuration. I do know that the commercial product IpswitchFtp does deal with the issue as this extract from it's log shows:
      ------------
      PASV
      227 Entering Passive Mode (192,168,13,11,195,129)
      connecting data channel to 192.168.13.11:195,129(50049)
      Substituting connection address 159.106.121.79 for private address 192.168.13.11 from PASV
      data channel connected to 159.106.121.79:195,129(50049)
      LIST
      125 List started OK
      transferred 4157 bytes in 0.078 seconds, 425.688 kbps ( 53.211 kBps), transfer succeeded.
      250 List completed successfully.
      QUIT
      ----------------------------
      I can take a shot at a fix if you want. I'll set some timeout, and if that fails, I'll use the original address

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              • Assignee:
                Unassigned
                Reporter:
                danieldamon daniel damon
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                Dates

                • Created:
                  Updated:
                  Resolved: