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https://issues.apache.org/jira/browse/NET-663?focusedWorklogId=247752&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-247752
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ASF GitHub Bot logged work on NET-663:
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Author: ASF GitHub Bot
Created on: 23/May/19 22:32
Start Date: 23/May/19 22:32
Worklog Time Spent: 10m
Work Description: mshenfield commented on pull request #40: [NET-663]
Retrieve socket host before closing in remote verification
URL: https://github.com/apache/commons-net/pull/40
This retrieves the socket host before closing the socket when remote
verification fails in order to get a non-null host address. In
[NET-663](https://issues.apache.org/jira/browse/NET-663),
`socket.getInetAddress()` returned a null after the socket was closed, causing
a `NullPointerException` instead of the more helpful error message intended.
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Issue Time Tracking
-------------------
Worklog Id: (was: 247752)
Time Spent: 20m (was: 10m)
> NullPointerException when FTPClient remote verification fails
> -------------------------------------------------------------
>
> Key: NET-663
> URL: https://issues.apache.org/jira/browse/NET-663
> Project: Commons Net
> Issue Type: Bug
> Components: FTP
> Affects Versions: 3.6
> Environment: OS: Linux
> Reporter: Max Shenfield
> Priority: Minor
> Labels: NullPointerException
> Time Spent: 20m
> Remaining Estimate: 0h
>
> At L934 of the {{FTPClient}} code, Apache does a check to see whether the
> data and control connections are at the same IP address ({{verifyRemote}}).
> If they differ, the data connection socket is closed and an exception is
> raised. This can be disabled, but is the default behavior
> ({{__remoteVerificationEnabled = true}}).
> I'm connecting to the FTP via a proxy. In my setup, the L934-939 code path
> where {{verifyRemote}} returns false always raises a
> {{java.lang.NullPointerException}}. {{socket.getInetAddress()}} seems to
> return {{null}} after {{socket.close}} is called, leading to
> {{socket.getInetAdress().getHostAddress()}} to raise the
> {{java.lang.NullPointerException}} at L938. This obfuscates a really useful
> error message ("Host attempting data connection is not the same as server")
> with a difficult to debug {{NullPointerException}}.
> Example State:
> {code}
> this.__remoteVerificationEnabled -> true
> this.getRemoteAddress().toString() -> "ftp.example.com/987.654.321.000"
> socket.getInetAddress().toString() -> "/123.456.789.000"
> {code}
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