Bug 234952 - deprecating behavior; netcat hostname resolution broken
deprecating behavior; netcat hostname resolution broken
Product: Fedora
Classification: Fedora
Component: nc (Show other bugs)
x86_64 Linux
medium Severity medium
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Assigned To: Radek Vokal
Ben Levenson
: Reopened
Depends On:
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Reported: 2007-04-02 22:47 EDT by Leon Smith
Modified: 2008-06-16 21:17 EDT (History)
1 user (show)

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Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Last Closed: 2008-06-16 21:17:11 EDT
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RHEL 7.3 requirements from Atomic Host:
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Description Leon Smith 2007-04-02 22:47:46 EDT
Description of problem:

netcat is unable to listen on a port, apparently because it is not able to parse
the command line properly.

Version-Release number of selected component (if applicable):

1.84-10.fc6.x86_64,   same issue with 1.84-3.fc6.i386

How reproducible:

Completely reproducable,  on my computer anyway.

Steps to Reproduce:
1.  /usr/bin/nc -l -p 8080

Actual results:

The following is written to stderr:

usage: nc [-46DdhklnrStUuvzC] [-i interval] [-p source_port]
          [-s source_ip_address] [-T ToS] [-w timeout] [-X proxy_version]
          [-x proxy_address[:port]] [hostname] [port[s]]  

Expected results:

no output,  should wait for a connection on port 8080 instead.

Additional info:
Comment 1 Jan Cholasta 2007-04-03 07:44:24 EDT
From the manual page:
>    -p source_port
>            Specifies the source port nc should use, subject to privilege
>            restrictions and availability.  It is an error to use this option
>            in conjunction with the -l option.

You should use 'nc -l 8080'
Comment 2 Leon Smith 2007-04-03 10:07:36 EDT
This is not standard netcat behavior.   In fact,  on machines recent version Red Hat Enterprise,   'nc -l 
8080' does not work.   You *must* use 'nc -l -s 8080',  otherwise,  netcat does not start listening    
Moreover, no deprecation of this behavior was ever done.     This caused me quite a bit of confusion 
that caused me to waste a few hours of my working day locating this issue, experimenting with other 
versions of nc and preinstalled versions of nc on other operating systems.

Furthermore,   I had experimented around with 'nc -l 8080',   and had concluded it wasn't listening on a 
port,   as it does on Red Hat Enterprise.   This is because nc hostname resolution is broken.

If you do:

nc -l 8080  

in one terminal,  and then

nc localhost 8080 

in another,  you will not be able to connect to the first terminal.   However,  you will be able connect if 
you use


Comment 3 Bug Zapper 2008-05-14 08:11:46 EDT
This message is a reminder that Fedora 7 is nearing the end of life. Approximately 30 (thirty) days from now Fedora will stop maintaining and issuing updates for Fedora 7. It is Fedora's policy to close all bug reports from releases that are no longer maintained. At that time this bug will be closed as WONTFIX if it remains open with a Fedora 'version' of '7'.

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Comment 4 Bug Zapper 2008-06-16 21:17:10 EDT
Fedora 7 changed to end-of-life (EOL) status on June 13, 2008. 
Fedora 7 is no longer maintained, which means that it will not 
receive any further security or bug fix updates. As a result we 
are closing this bug. 

If you can reproduce this bug against a currently maintained version 
of Fedora please feel free to reopen this bug against that version.

Thank you for reporting this bug and we are sorry it could not be fixed.

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