[NET-363] Can't connect to a server behind firewall in passive mode

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 2.2
• Fix Version/s: 3.0
• Component/s: FTP

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.

• Assignee: Unassigned
• Reporter: daniel damon
• Created: 04/Mar/11 23:10
• Updated: 29/Feb/16 16:21
• Resolved: 05/Mar/11 21:22

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

Issue Links

• is duplicated by: NET-296 java.net.SocketException: Operation timed out error while entering Passive mode