[RFC PATCH] netconsole.txt: "nc" needs "-p" to specify the listening port

[RFC PATCH] netconsole.txt: "nc" needs "-p" to specify the listening port

[Dirk Gouders]

Hi Jesse,

I would like to ask you to check if the documentation of "nc" in
netconsole.txt is still correct.  I tried two different netcat packages
and both require "-p" to specify the listening port.  I am wondering if
that changed after the use of "nc" has been documented.

Best regards,

Dirk

Signed-off-by: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
---
 Documentation/networking/netconsole.txt |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt
index 8d02207..ffe30a7 100644
--- a/Documentation/networking/netconsole.txt
+++ b/Documentation/networking/netconsole.txt
@@ -52,7 +52,7 @@ initialized and attempts to bring up the supplied dev at the supplied
 address.
 
 The remote host can run either 'netcat -u -l -p <port>',
-'nc -l -u <port>' or syslogd.
+'nc -l -u -p <port>' or syslogd.
 
 Dynamic reconfiguration:
 ========================
-- 
1.7.8.6

Re: [RFC PATCH] netconsole.txt: "nc" needs "-p" to specify the listening port

[Cong Wang]

On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders
<gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
> Hi Jesse,
>
> I would like to ask you to check if the documentation of "nc" in
> netconsole.txt is still correct.  I tried two different netcat packages
> and both require "-p" to specify the listening port.  I am wondering if
> that changed after the use of "nc" has been documented.

On Fedora 16, `nc -u -l <port number>` works fine.

Re: [RFC PATCH] netconsole.txt: "nc" needs "-p" to specify the listening port

[Dirk Gouders]

Cong Wang <xiyou.wangcong@gmail.com> writes:

> On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders
> <gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
>> Hi Jesse,
>>
>> I would like to ask you to check if the documentation of "nc" in
>> netconsole.txt is still correct.  I tried two different netcat packages
>> and both require "-p" to specify the listening port.  I am wondering if
>> that changed after the use of "nc" has been documented.
>
> On Fedora 16, `nc -u -l <port number>` works fine.

Thanks for checking that.

If the information I found is correct, Fedora uses OpenBSD's nc
codebase.  The two netcat packages I tested on a Gentoo system differ in
requiring the -p switch for the port specification.

Dirk

Re: [RFC PATCH] netconsole.txt: "nc" needs "-p" to specify the listening port

[Borislav Petkov]

On Fri, Jul 27, 2012 at 11:24:53AM +0200, Dirk Gouders wrote:
> Cong Wang <xiyou.wangcong@gmail.com> writes:
> 
> > On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders
> > <gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
> >> Hi Jesse,
> >>
> >> I would like to ask you to check if the documentation of "nc" in
> >> netconsole.txt is still correct.  I tried two different netcat packages
> >> and both require "-p" to specify the listening port.  I am wondering if
> >> that changed after the use of "nc" has been documented.
> >
> > On Fedora 16, `nc -u -l <port number>` works fine.
> 
> Thanks for checking that.
> 
> If the information I found is correct, Fedora uses OpenBSD's nc
> codebase.  The two netcat packages I tested on a Gentoo system differ in
> requiring the -p switch for the port specification.

So say exactly that in the doc: that the *BSD's version of nc doesn't
need the port number specified with '-p' and you're covered.

-- 
Regards/Gruss,
Boris.

Re: [RFC PATCH] netconsole.txt: "nc" needs "-p" to specify the listening port

[Dirk Gouders]

Borislav Petkov <bp@alien8.de> writes:

> On Fri, Jul 27, 2012 at 11:24:53AM +0200, Dirk Gouders wrote:
>> Cong Wang <xiyou.wangcong@gmail.com> writes:
>> 
>> > On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders
>> > <gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
>> >> Hi Jesse,
>> >>
>> >> I would like to ask you to check if the documentation of "nc" in
>> >> netconsole.txt is still correct.  I tried two different netcat packages
>> >> and both require "-p" to specify the listening port.  I am wondering if
>> >> that changed after the use of "nc" has been documented.
>> >
>> > On Fedora 16, `nc -u -l <port number>` works fine.
>> 
>> Thanks for checking that.
>> 
>> If the information I found is correct, Fedora uses OpenBSD's nc
>> codebase.  The two netcat packages I tested on a Gentoo system differ in
>> requiring the -p switch for the port specification.
>
> So say exactly that in the doc: that the *BSD's version of nc doesn't
> need the port number specified with '-p' and you're covered.

OK, I tried that in the attached patch.
I'm not sure if every exeption needs to/should be documented, though.

Dirk

>From 3cdeac3e814471053129145c5fa8391acb365fd8 Mon Sep 17 00:00:00 2001
From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
Date: Sat, 28 Jul 2012 12:32:49 +0200
Subject: [PATCH] netconsole.txt: non-BSD versions of nc(1) require '-p'
 switch

Gentoo for example uses non-BSD versions of nc(1) which require
the '-p' switch to specify the listening port.
---
 Documentation/networking/netconsole.txt |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt
index 8d02207..9a362f8 100644
--- a/Documentation/networking/netconsole.txt
+++ b/Documentation/networking/netconsole.txt
@@ -52,7 +52,8 @@ initialized and attempts to bring up the supplied dev at the supplied
 address.
 
 The remote host can run either 'netcat -u -l -p <port>',
-'nc -l -u <port>' or syslogd.
+'nc -l -u <port>' (BSD version of nc(1) e.g. Fedora),
+'nc -l -u -p <port>' or syslogd.
 
 Dynamic reconfiguration:
 ========================
-- 
1.7.8.6

Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port, [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port

[Milton Miller]

[adding Rob as Doc maintanier]

On Sat, 28 Jul 2012 about 11:08:16 -0000, Dirk Gouders wrote:
> Borislav Petkov <bp@alien8.de> writes:
> 
> > On Fri, Jul 27, 2012 at 11:24:53AM +0200, Dirk Gouders wrote:
> >> Cong Wang <xiyou.wangcong@gmail.com> writes:
> >> 
> >> > On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders
> >> > <gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
> >> >> Hi Jesse,
> >> >>
> >> >> I would like to ask you to check if the documentation of "nc" in
> >> >> netconsole.txt is still correct.  I tried two different netcat packages
> >> >> and both require "-p" to specify the listening port.  I am wondering if
> >> >> that changed after the use of "nc" has been documented.
> >> >
> >> > On Fedora 16, `nc -u -l <port number>` works fine.
> >> 
> >> Thanks for checking that.
> >> 
> >> If the information I found is correct, Fedora uses OpenBSD's nc
> >> codebase.  The two netcat packages I tested on a Gentoo system differ in
> >> requiring the -p switch for the port specification.
> >
> > So say exactly that in the doc: that the *BSD's version of nc doesn't
> > need the port number specified with '-p' and you're covered.
> OK, I tried that in the attached patch.
> I'm not sure if every exeption needs to/should be documented, though.
> 
> >From 3cdeac3e814471053129145c5fa8391acb365fd8 Mon Sep 17 00:00:00 2001
> From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
> Date: Sat, 28 Jul 2012 12:32:49 +0200
> Subject: [PATCH] netconsole.txt: non-BSD versions of nc(1) require '-p'
>  switch
> 
> Gentoo for example uses non-BSD versions of nc(1) which require
> the '-p' switch to specify the listening port.
> 
> ---
> Documentation/networking/netconsole.txt |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt
> index 8d02207..9a362f8 100644
> --- a/Documentation/networking/netconsole.txt
> +++ b/Documentation/networking/netconsole.txt
> @@ -52,7 +52,8 @@ initialized and attempts to bring up the supplied dev at the supplied
>  address.
>  
>  The remote host can run either 'netcat -u -l -p <port>',

So the above line shows usage with -p

> -'nc -l -u <port>' or syslogd.
> +'nc -l -u <port>' (BSD version of nc(1) e.g. Fedora),

now you add a comment about BSD and say Fedora which is not obviously
BSD (this is Documentation; reading the git history for clarification
is not approprate).

> +'nc -l -u -p <port>' or syslogd.

And now you add the original -p which you probably skipped over
since it was on the previous line?


>  
>  Dynamic reconfiguration:
>  ========================

milton

Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port

[Dirk Gouders]

Milton Miller <miltonm@bga.com> writes:

> [adding Rob as Doc maintanier]
>
> On Sat, 28 Jul 2012 about 11:08:16 -0000, Dirk Gouders wrote:
>> Borislav Petkov <bp@alien8.de> writes:
>> 
>> > On Fri, Jul 27, 2012 at 11:24:53AM +0200, Dirk Gouders wrote:
>> >> Cong Wang <xiyou.wangcong@gmail.com> writes:
>> >> 
>> >> > On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders
>> >> > <gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
>> >> >> Hi Jesse,
>> >> >>
>> >> >> I would like to ask you to check if the documentation of "nc" in
>> >> >> netconsole.txt is still correct.  I tried two different netcat packages
>> >> >> and both require "-p" to specify the listening port.  I am wondering if
>> >> >> that changed after the use of "nc" has been documented.
>> >> >
>> >> > On Fedora 16, `nc -u -l <port number>` works fine.
>> >> 
>> >> Thanks for checking that.
>> >> 
>> >> If the information I found is correct, Fedora uses OpenBSD's nc
>> >> codebase.  The two netcat packages I tested on a Gentoo system differ in
>> >> requiring the -p switch for the port specification.
>> >
>> > So say exactly that in the doc: that the *BSD's version of nc doesn't
>> > need the port number specified with '-p' and you're covered.
>> OK, I tried that in the attached patch.
>> I'm not sure if every exeption needs to/should be documented, though.
>> 
>> >From 3cdeac3e814471053129145c5fa8391acb365fd8 Mon Sep 17 00:00:00 2001
>> From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
>> Date: Sat, 28 Jul 2012 12:32:49 +0200
>> Subject: [PATCH] netconsole.txt: non-BSD versions of nc(1) require '-p'
>>  switch
>> 
>> Gentoo for example uses non-BSD versions of nc(1) which require
>> the '-p' switch to specify the listening port.
>> 
>> ---
>> Documentation/networking/netconsole.txt |    3 ++-
>>  1 files changed, 2 insertions(+), 1 deletions(-)
>> 
>> diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt
>> index 8d02207..9a362f8 100644
>> --- a/Documentation/networking/netconsole.txt
>> +++ b/Documentation/networking/netconsole.txt
>> @@ -52,7 +52,8 @@ initialized and attempts to bring up the supplied dev at the supplied
>>  address.
>>  
>>  The remote host can run either 'netcat -u -l -p <port>',
>
> So the above line shows usage with -p
>
>> -'nc -l -u <port>' or syslogd.
>> +'nc -l -u <port>' (BSD version of nc(1) e.g. Fedora),
>
> now you add a comment about BSD and say Fedora which is not obviously
> BSD (this is Documentation; reading the git history for clarification
> is not approprate).

Thanks for your comments.
Perhaps I should have written "(BSD version of nc(1) which is used on
Fedora, for example)"

>> +'nc -l -u -p <port>' or syslogd.
>
> And now you add the original -p which you probably skipped over
> since it was on the previous line?

Well, this has been intentionally.

Probably this is because of the Gentoo system I use as a reference.
It offers three netcat packages, one is "gnu-netcat" which provides
/usr/bin/netcat, the other two are "netcat" and "netcat6", both of which
provide /usr/bin/nc (those packages cannot be installed at the same
time).  All of these netcat implementations require the '-p' switch.

I will check other distributions to see what netcat implementations they
provide; probably Gentoo is an exception in which case it might be
overdone to change the documentation for that special case...

Dirk

>
>>  
>>  Dynamic reconfiguration:
>>  ========================
>
> milton

Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port

[Rob Landley]

On 07/29/2012 03:40 AM, Milton Miller wrote:
> [adding Rob as Doc maintanier]
> 
> On Sat, 28 Jul 2012 about 11:08:16 -0000, Dirk Gouders wrote:
>> Borislav Petkov <bp@alien8.de> writes:
>>
>>> On Fri, Jul 27, 2012 at 11:24:53AM +0200, Dirk Gouders wrote:
>>>> Cong Wang <xiyou.wangcong@gmail.com> writes:
>>>>
>>>>> On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders
>>>>> <gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
>>>>>> Hi Jesse,
>>>>>>
>>>>>> I would like to ask you to check if the documentation of "nc" in
>>>>>> netconsole.txt is still correct.  I tried two different netcat packages
>>>>>> and both require "-p" to specify the listening port.  I am wondering if
>>>>>> that changed after the use of "nc" has been documented.
>>>>>
>>>>> On Fedora 16, `nc -u -l <port number>` works fine.
>>>>
>>>> Thanks for checking that.
>>>>
>>>> If the information I found is correct, Fedora uses OpenBSD's nc
>>>> codebase.  The two netcat packages I tested on a Gentoo system differ in
>>>> requiring the -p switch for the port specification.
>>>
>>> So say exactly that in the doc: that the *BSD's version of nc doesn't
>>> need the port number specified with '-p' and you're covered.
>> OK, I tried that in the attached patch.
>> I'm not sure if every exeption needs to/should be documented, though.
>>
>> >From 3cdeac3e814471053129145c5fa8391acb365fd8 Mon Sep 17 00:00:00 2001
>> From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
>> Date: Sat, 28 Jul 2012 12:32:49 +0200
>> Subject: [PATCH] netconsole.txt: non-BSD versions of nc(1) require '-p'
>>  switch
>>
>> Gentoo for example uses non-BSD versions of nc(1) which require
>> the '-p' switch to specify the listening port.
>>
>> ---
>> Documentation/networking/netconsole.txt |    3 ++-
>>  1 files changed, 2 insertions(+), 1 deletions(-)

Did this ever resolve to a specific recommended patch? The one at the
start of the thread:

 http://lkml.indiana.edu/hypermail/linux/kernel/1207.3/01995.html

Apparently isn't it...?

Rob
-- 
GNU/Linux isn't: Linux=GPLv2, GNU=GPLv3+, they can't share code.
Either it's "mere aggregation", or a license violation.  Pick one.

Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port

[Dirk Gouders]

Rob Landley <rob@landley.net> writes:

> On 07/29/2012 03:40 AM, Milton Miller wrote:
>> [adding Rob as Doc maintanier]
>> 
>> On Sat, 28 Jul 2012 about 11:08:16 -0000, Dirk Gouders wrote:
>>> Borislav Petkov <bp@alien8.de> writes:
>>>
>>>> On Fri, Jul 27, 2012 at 11:24:53AM +0200, Dirk Gouders wrote:
>>>>> Cong Wang <xiyou.wangcong@gmail.com> writes:
>>>>>
>>>>>> On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders
>>>>>> <gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
>>>>>>> Hi Jesse,
>>>>>>>
>>>>>>> I would like to ask you to check if the documentation of "nc" in
>>>>>>> netconsole.txt is still correct.  I tried two different netcat packages
>>>>>>> and both require "-p" to specify the listening port.  I am wondering if
>>>>>>> that changed after the use of "nc" has been documented.
>>>>>>
>>>>>> On Fedora 16, `nc -u -l <port number>` works fine.
>>>>>
>>>>> Thanks for checking that.
>>>>>
>>>>> If the information I found is correct, Fedora uses OpenBSD's nc
>>>>> codebase.  The two netcat packages I tested on a Gentoo system differ in
>>>>> requiring the -p switch for the port specification.
>>>>
>>>> So say exactly that in the doc: that the *BSD's version of nc doesn't
>>>> need the port number specified with '-p' and you're covered.
>>> OK, I tried that in the attached patch.
>>> I'm not sure if every exeption needs to/should be documented, though.
>>>
>>> >From 3cdeac3e814471053129145c5fa8391acb365fd8 Mon Sep 17 00:00:00 2001
>>> From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
>>> Date: Sat, 28 Jul 2012 12:32:49 +0200
>>> Subject: [PATCH] netconsole.txt: non-BSD versions of nc(1) require '-p'
>>>  switch
>>>
>>> Gentoo for example uses non-BSD versions of nc(1) which require
>>> the '-p' switch to specify the listening port.
>>>
>>> ---
>>> Documentation/networking/netconsole.txt |    3 ++-
>>>  1 files changed, 2 insertions(+), 1 deletions(-)
>
> Did this ever resolve to a specific recommended patch? The one at the
> start of the thread:
>
>  http://lkml.indiana.edu/hypermail/linux/kernel/1207.3/01995.html
>
> Apparently isn't it...?

Sorry for the delay.
I tested the situation on a few distributions and am still thinking
about a proper way to write it in a way without netconsole.txt becoming
a kind of "netcat.txt".

I would be glad about comments to what I currently have -- also, because
I am not a native English speaker:

------------------------------------------------------------------------
The remote host can run syslogd or netcat to receive the kernel
messages.  On distributions using a BSD-based netcat version
(e.g. Fedora, openSUSE and Ubuntu) the listening port must be
specified without the -p switch:

'nc -u -l -p <port>' / 'nc -u -l <port>' or
'netcat -u -l -p <port>' / 'netcat -u -l <port>'
------------------------------------------------------------------------

At the end, I also attach what I have noted during the tests with the
different distributions.

Dirk

------------------------------------------------------------------------
Problem on systems where the gnu-netcat package provides a symbolic
link /usr/bin/nc -> /usr/bin/netcat:

gnu-netcat requires -p to specify the local port but does not complain
if invoked as `nc -l -u <port>'; you need to use -v to see that it
does not do what you might expect:

# nc -l -u 4444 -v
Warning: Inverse name lookup failed for `0.0.17.92'
------------------------------------------------------------------------

Distro		Package						needs -p
		Command invocation
========================================================================
Arch		gnu-netcat					yes
(Website	nc | netcat
 documentation)
		openbsd-netcat					no
		nc.openbsd
------------------------------------------------------------------------
Debian-6.0.5	netcat-openbsd					no 
		nc | netcat | nc.openbsd		   
		                                   
		netcat / netcat-traditional (preinstalled)	yes
		nc | netcat
		                                   
		netcat6						yes
		nc | netcat | nc6
------------------------------------------------------------------------
Fedora-17	nc (preinstalled)				no
		nc

		nc6
		nc6						yes
------------------------------------------------------------------------
Gentoo		gnu-netcat					yes
		netcat

		netcat						yes
		nc

		netcat6						yes
		nc | nc6
------------------------------------------------------------------------
OpenSUSE-12.1	netcat-openbsd					no
		nc | netcat
------------------------------------------------------------------------
Ubuntu-12.04	netcat-openbsd (preinstalled)			no 
Desktop		nc | netcat | nc.openbsd
		                                   
		netcat / netcat-traditional			yes
		nc | netcat		   
		                                   
		netcat6						yes
		nc | netcat | nc6
------------------------------------------------------------------------

Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port

[Dirk Gouders]

Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de> writes:

> Rob Landley <rob@landley.net> writes:
>
>> On 07/29/2012 03:40 AM, Milton Miller wrote:
>>> [adding Rob as Doc maintanier]
>>> 
>>> On Sat, 28 Jul 2012 about 11:08:16 -0000, Dirk Gouders wrote:
>>>> Borislav Petkov <bp@alien8.de> writes:
>>>>
>>>>> On Fri, Jul 27, 2012 at 11:24:53AM +0200, Dirk Gouders wrote:
>>>>>> Cong Wang <xiyou.wangcong@gmail.com> writes:
>>>>>>
>>>>>>> On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders
>>>>>>> <gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
>>>>>>>> Hi Jesse,
>>>>>>>>
>>>>>>>> I would like to ask you to check if the documentation of "nc" in
>>>>>>>> netconsole.txt is still correct.  I tried two different netcat packages
>>>>>>>> and both require "-p" to specify the listening port.  I am wondering if
>>>>>>>> that changed after the use of "nc" has been documented.
>>>>>>>
>>>>>>> On Fedora 16, `nc -u -l <port number>` works fine.
>>>>>>
>>>>>> Thanks for checking that.
>>>>>>
>>>>>> If the information I found is correct, Fedora uses OpenBSD's nc
>>>>>> codebase.  The two netcat packages I tested on a Gentoo system differ in
>>>>>> requiring the -p switch for the port specification.
>>>>>
>>>>> So say exactly that in the doc: that the *BSD's version of nc doesn't
>>>>> need the port number specified with '-p' and you're covered.
>>>> OK, I tried that in the attached patch.
>>>> I'm not sure if every exeption needs to/should be documented, though.
>>>>
>>>> >From 3cdeac3e814471053129145c5fa8391acb365fd8 Mon Sep 17 00:00:00 2001
>>>> From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
>>>> Date: Sat, 28 Jul 2012 12:32:49 +0200
>>>> Subject: [PATCH] netconsole.txt: non-BSD versions of nc(1) require '-p'
>>>>  switch
>>>>
>>>> Gentoo for example uses non-BSD versions of nc(1) which require
>>>> the '-p' switch to specify the listening port.
>>>>
>>>> ---
>>>> Documentation/networking/netconsole.txt |    3 ++-
>>>>  1 files changed, 2 insertions(+), 1 deletions(-)
>>
>> Did this ever resolve to a specific recommended patch? The one at the
>> start of the thread:
>>
>>  http://lkml.indiana.edu/hypermail/linux/kernel/1207.3/01995.html
>>
>> Apparently isn't it...?
>
> Sorry for the delay.
> I tested the situation on a few distributions and am still thinking
> about a proper way to write it in a way without netconsole.txt becoming
> a kind of "netcat.txt".
>
> I would be glad about comments to what I currently have -- also, because
> I am not a native English speaker:
>
> ------------------------------------------------------------------------
> The remote host can run syslogd or netcat to receive the kernel
> messages.  On distributions using a BSD-based netcat version
> (e.g. Fedora, openSUSE and Ubuntu) the listening port must be
> specified without the -p switch:
>
> 'nc -u -l -p <port>' / 'nc -u -l <port>' or
> 'netcat -u -l -p <port>' / 'netcat -u -l <port>'
> ------------------------------------------------------------------------
>
> At the end, I also attach what I have noted during the tests with the
> different distributions.
>
> Dirk
>
> ------------------------------------------------------------------------
> Problem on systems where the gnu-netcat package provides a symbolic
> link /usr/bin/nc -> /usr/bin/netcat:
>
> gnu-netcat requires -p to specify the local port but does not complain
> if invoked as `nc -l -u <port>'; you need to use -v to see that it
> does not do what you might expect:
>
> # nc -l -u 4444 -v
> Warning: Inverse name lookup failed for `0.0.17.92'
> ------------------------------------------------------------------------
>
> Distro		Package						needs -p
> 		Command invocation
> ========================================================================
> Arch		gnu-netcat					yes
> (Website	nc | netcat
>  documentation)
> 		openbsd-netcat					no
> 		nc.openbsd
> ------------------------------------------------------------------------
> Debian-6.0.5	netcat-openbsd					no 
> 		nc | netcat | nc.openbsd		   
> 		                                   
> 		netcat / netcat-traditional (preinstalled)	yes
> 		nc | netcat
> 		                                   
> 		netcat6						yes
> 		nc | netcat | nc6
> ------------------------------------------------------------------------
> Fedora-17	nc (preinstalled)				no
> 		nc
>
> 		nc6
> 		nc6						yes
> ------------------------------------------------------------------------
> Gentoo		gnu-netcat					yes
> 		netcat
>
> 		netcat						yes
> 		nc
>
> 		netcat6						yes
> 		nc | nc6
> ------------------------------------------------------------------------
> OpenSUSE-12.1	netcat-openbsd					no
> 		nc | netcat
> ------------------------------------------------------------------------
> Ubuntu-12.04	netcat-openbsd (preinstalled)			no 
> Desktop		nc | netcat | nc.openbsd
> 		                                   
> 		netcat / netcat-traditional			yes
> 		nc | netcat		   
> 		                                   
> 		netcat6						yes
> 		nc | netcat | nc6
> ------------------------------------------------------------------------

Here is a patch that also includes Jan's suggestion for socat(1).

The problem with the patch is that the netcat part does not cover every
possible distribution/netcat-package situation but in my opinion it is a
bearable compromise with respect to keeping the example section compact.

Dirk

>From d756d2750e4cf07d3c0942dc3c491d57631d4338 Mon Sep 17 00:00:00 2001
From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
Date: Thu, 2 Aug 2012 22:20:16 +0200
Subject: [PATCH] netconsole.txt: revision of examples for the receiver of kernel messages

There are at least 4 implementations of netcat with the BSD-based
being the only one that has to be used without the -p switch to
specify the listening port.

Jan Engelhardt suggested to add an example for socat(1).
---
 Documentation/networking/netconsole.txt |   19 +++++++++++++++++--
 1 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt
index 8d02207..2e9e0ae2 100644
--- a/Documentation/networking/netconsole.txt
+++ b/Documentation/networking/netconsole.txt
@@ -51,8 +51,23 @@ Built-in netconsole starts immediately after the TCP stack is
 initialized and attempts to bring up the supplied dev at the supplied
 address.
 
-The remote host can run either 'netcat -u -l -p <port>',
-'nc -l -u <port>' or syslogd.
+The remote host has several options to receive the kernel messages,
+for example:
+
+1) syslogd
+
+2) netcat
+
+   On distributions using a BSD-based netcat version (e.g. Fedora,
+   openSUSE and Ubuntu) the listening port must be specified without
+   the -p switch:
+
+   'nc -u -l -p <port>' / 'nc -u -l <port>' or
+   'netcat -u -l -p <port>' / 'netcat -u -l <port>'
+
+3) socat
+
+   'socat udp-recv:<port> -'
 
 Dynamic reconfiguration:
 ========================
-- 
1.7.8.6

Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port

[Jesse Barnes]

On Thu, 02 Aug 2012 22:39:28 +0200
Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de> wrote:

> Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de> writes:
> 
> > Rob Landley <rob@landley.net> writes:
> >
> >> On 07/29/2012 03:40 AM, Milton Miller wrote:
> >>> [adding Rob as Doc maintanier]
> >>> 
> >>> On Sat, 28 Jul 2012 about 11:08:16 -0000, Dirk Gouders wrote:
> >>>> Borislav Petkov <bp@alien8.de> writes:
> >>>>
> >>>>> On Fri, Jul 27, 2012 at 11:24:53AM +0200, Dirk Gouders wrote:
> >>>>>> Cong Wang <xiyou.wangcong@gmail.com> writes:
> >>>>>>
> >>>>>>> On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders
> >>>>>>> <gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
> >>>>>>>> Hi Jesse,
> >>>>>>>>
> >>>>>>>> I would like to ask you to check if the documentation of "nc" in
> >>>>>>>> netconsole.txt is still correct.  I tried two different netcat packages
> >>>>>>>> and both require "-p" to specify the listening port.  I am wondering if
> >>>>>>>> that changed after the use of "nc" has been documented.
> >>>>>>>
> >>>>>>> On Fedora 16, `nc -u -l <port number>` works fine.
> >>>>>>
> >>>>>> Thanks for checking that.
> >>>>>>
> >>>>>> If the information I found is correct, Fedora uses OpenBSD's nc
> >>>>>> codebase.  The two netcat packages I tested on a Gentoo system differ in
> >>>>>> requiring the -p switch for the port specification.
> >>>>>
> >>>>> So say exactly that in the doc: that the *BSD's version of nc doesn't
> >>>>> need the port number specified with '-p' and you're covered.
> >>>> OK, I tried that in the attached patch.
> >>>> I'm not sure if every exeption needs to/should be documented, though.
> >>>>
> >>>> >From 3cdeac3e814471053129145c5fa8391acb365fd8 Mon Sep 17 00:00:00 2001
> >>>> From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
> >>>> Date: Sat, 28 Jul 2012 12:32:49 +0200
> >>>> Subject: [PATCH] netconsole.txt: non-BSD versions of nc(1) require '-p'
> >>>>  switch
> >>>>
> >>>> Gentoo for example uses non-BSD versions of nc(1) which require
> >>>> the '-p' switch to specify the listening port.
> >>>>
> >>>> ---
> >>>> Documentation/networking/netconsole.txt |    3 ++-
> >>>>  1 files changed, 2 insertions(+), 1 deletions(-)
> >>
> >> Did this ever resolve to a specific recommended patch? The one at the
> >> start of the thread:
> >>
> >>  http://lkml.indiana.edu/hypermail/linux/kernel/1207.3/01995.html
> >>
> >> Apparently isn't it...?
> >
> > Sorry for the delay.
> > I tested the situation on a few distributions and am still thinking
> > about a proper way to write it in a way without netconsole.txt becoming
> > a kind of "netcat.txt".
> >
> > I would be glad about comments to what I currently have -- also, because
> > I am not a native English speaker:
> >
> > ------------------------------------------------------------------------
> > The remote host can run syslogd or netcat to receive the kernel
> > messages.  On distributions using a BSD-based netcat version
> > (e.g. Fedora, openSUSE and Ubuntu) the listening port must be
> > specified without the -p switch:
> >
> > 'nc -u -l -p <port>' / 'nc -u -l <port>' or
> > 'netcat -u -l -p <port>' / 'netcat -u -l <port>'
> > ------------------------------------------------------------------------
> >
> > At the end, I also attach what I have noted during the tests with the
> > different distributions.
> >
> > Dirk
> >
> > ------------------------------------------------------------------------
> > Problem on systems where the gnu-netcat package provides a symbolic
> > link /usr/bin/nc -> /usr/bin/netcat:
> >
> > gnu-netcat requires -p to specify the local port but does not complain
> > if invoked as `nc -l -u <port>'; you need to use -v to see that it
> > does not do what you might expect:
> >
> > # nc -l -u 4444 -v
> > Warning: Inverse name lookup failed for `0.0.17.92'
> > ------------------------------------------------------------------------
> >
> > Distro		Package						needs -p
> > 		Command invocation
> > ========================================================================
> > Arch		gnu-netcat					yes
> > (Website	nc | netcat
> >  documentation)
> > 		openbsd-netcat					no
> > 		nc.openbsd
> > ------------------------------------------------------------------------
> > Debian-6.0.5	netcat-openbsd					no 
> > 		nc | netcat | nc.openbsd		   
> > 		                                   
> > 		netcat / netcat-traditional (preinstalled)	yes
> > 		nc | netcat
> > 		                                   
> > 		netcat6						yes
> > 		nc | netcat | nc6
> > ------------------------------------------------------------------------
> > Fedora-17	nc (preinstalled)				no
> > 		nc
> >
> > 		nc6
> > 		nc6						yes
> > ------------------------------------------------------------------------
> > Gentoo		gnu-netcat					yes
> > 		netcat
> >
> > 		netcat						yes
> > 		nc
> >
> > 		netcat6						yes
> > 		nc | nc6
> > ------------------------------------------------------------------------
> > OpenSUSE-12.1	netcat-openbsd					no
> > 		nc | netcat
> > ------------------------------------------------------------------------
> > Ubuntu-12.04	netcat-openbsd (preinstalled)			no 
> > Desktop		nc | netcat | nc.openbsd
> > 		                                   
> > 		netcat / netcat-traditional			yes
> > 		nc | netcat		   
> > 		                                   
> > 		netcat6						yes
> > 		nc | netcat | nc6
> > ------------------------------------------------------------------------
> 
> Here is a patch that also includes Jan's suggestion for socat(1).
> 
> The problem with the patch is that the netcat part does not cover every
> possible distribution/netcat-package situation but in my opinion it is a
> bearable compromise with respect to keeping the example section compact.
> 
> Dirk
> 
> From d756d2750e4cf07d3c0942dc3c491d57631d4338 Mon Sep 17 00:00:00 2001
> From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
> Date: Thu, 2 Aug 2012 22:20:16 +0200
> Subject: [PATCH] netconsole.txt: revision of examples for the receiver of kernel messages
> 
> There are at least 4 implementations of netcat with the BSD-based
> being the only one that has to be used without the -p switch to
> specify the listening port.
> 
> Jan Engelhardt suggested to add an example for socat(1).
> ---
>  Documentation/networking/netconsole.txt |   19 +++++++++++++++++--
>  1 files changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt
> index 8d02207..2e9e0ae2 100644
> --- a/Documentation/networking/netconsole.txt
> +++ b/Documentation/networking/netconsole.txt
> @@ -51,8 +51,23 @@ Built-in netconsole starts immediately after the TCP stack is
>  initialized and attempts to bring up the supplied dev at the supplied
>  address.
>  
> -The remote host can run either 'netcat -u -l -p <port>',
> -'nc -l -u <port>' or syslogd.
> +The remote host has several options to receive the kernel messages,
> +for example:
> +
> +1) syslogd
> +
> +2) netcat
> +
> +   On distributions using a BSD-based netcat version (e.g. Fedora,
> +   openSUSE and Ubuntu) the listening port must be specified without
> +   the -p switch:
> +
> +   'nc -u -l -p <port>' / 'nc -u -l <port>' or
> +   'netcat -u -l -p <port>' / 'netcat -u -l <port>'
> +
> +3) socat
> +
> +   'socat udp-recv:<port> -'
>  
>  Dynamic reconfiguration:
>  ========================

Looks good to me, thanks Dirk.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

-- 
Jesse Barnes, Intel Open Source Technology Center

Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port

[Cong Wang]

On Fri, Aug 3, 2012 at 4:39 AM, Dirk Gouders
<gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
>
> From d756d2750e4cf07d3c0942dc3c491d57631d4338 Mon Sep 17 00:00:00 2001
> From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
> Date: Thu, 2 Aug 2012 22:20:16 +0200
> Subject: [PATCH] netconsole.txt: revision of examples for the receiver of kernel messages
>
> There are at least 4 implementations of netcat with the BSD-based
> being the only one that has to be used without the -p switch to
> specify the listening port.
>
> Jan Engelhardt suggested to add an example for socat(1).


Looks good, but you missed your SOB.

Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port

[Dirk Gouders]

Cong Wang <xiyou.wangcong@gmail.com> writes:

> On Fri, Aug 3, 2012 at 4:39 AM, Dirk Gouders
> <gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
>>
>> From d756d2750e4cf07d3c0942dc3c491d57631d4338 Mon Sep 17 00:00:00 2001
>> From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
>> Date: Thu, 2 Aug 2012 22:20:16 +0200
>> Subject: [PATCH] netconsole.txt: revision of examples for the receiver of kernel messages
>>
>> There are at least 4 implementations of netcat with the BSD-based
>> being the only one that has to be used without the -p switch to
>> specify the listening port.
>>
>> Jan Engelhardt suggested to add an example for socat(1).
>
>
> Looks good, but you missed your SOB.

Thanks for noticing that, attached is the amended patch.

Dirk

>From b3aec70d785d338b1b643fece6606cd32addaf0c Mon Sep 17 00:00:00 2001
From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
Date: Thu, 2 Aug 2012 22:20:16 +0200
Subject: [PATCH] netconsole.txt: revision of examples for the receiver of kernel messages

There are at least 4 implementations of netcat with the BSD-based
being the only one that has to be used without the -p switch to
specify the listening port.

Jan Engelhardt suggested to add an example for socat(1).

Signed-off-by: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
---
 Documentation/networking/netconsole.txt |   19 +++++++++++++++++--
 1 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt
index 8d02207..2e9e0ae2 100644
--- a/Documentation/networking/netconsole.txt
+++ b/Documentation/networking/netconsole.txt
@@ -51,8 +51,23 @@ Built-in netconsole starts immediately after the TCP stack is
 initialized and attempts to bring up the supplied dev at the supplied
 address.
 
-The remote host can run either 'netcat -u -l -p <port>',
-'nc -l -u <port>' or syslogd.
+The remote host has several options to receive the kernel messages,
+for example:
+
+1) syslogd
+
+2) netcat
+
+   On distributions using a BSD-based netcat version (e.g. Fedora,
+   openSUSE and Ubuntu) the listening port must be specified without
+   the -p switch:
+
+   'nc -u -l -p <port>' / 'nc -u -l <port>' or
+   'netcat -u -l -p <port>' / 'netcat -u -l <port>'
+
+3) socat
+
+   'socat udp-recv:<port> -'
 
 Dynamic reconfiguration:
 ========================
-- 
1.7.8.6

Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port

[Cong Wang]

On 08/03/2012 02:33 PM, Dirk Gouders wrote:
>
>  From b3aec70d785d338b1b643fece6606cd32addaf0c Mon Sep 17 00:00:00 2001
> From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
> Date: Thu, 2 Aug 2012 22:20:16 +0200
> Subject: [PATCH] netconsole.txt: revision of examples for the receiver of kernel messages
>
> There are at least 4 implementations of netcat with the BSD-based
> being the only one that has to be used without the -p switch to
> specify the listening port.
>
> Jan Engelhardt suggested to add an example for socat(1).
>
> Signed-off-by: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>

It looks like no one takes this patch, so I will take it together with 
my other netpoll/netconsole patches and send them to netdev.

Thanks!

Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port

[Dirk Gouders]

Cong Wang <xiyou.wangcong@gmail.com> writes:

> On 08/03/2012 02:33 PM, Dirk Gouders wrote:
>>
>>  From b3aec70d785d338b1b643fece6606cd32addaf0c Mon Sep 17 00:00:00 2001
>> From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
>> Date: Thu, 2 Aug 2012 22:20:16 +0200
>> Subject: [PATCH] netconsole.txt: revision of examples for the receiver of kernel messages
>>
>> There are at least 4 implementations of netcat with the BSD-based
>> being the only one that has to be used without the -p switch to
>> specify the listening port.
>>
>> Jan Engelhardt suggested to add an example for socat(1).
>>
>> Signed-off-by: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
>
> It looks like no one takes this patch, so I will take it together with
> my other netpoll/netconsole patches and send them to netdev.

Thank you for taking care of it.

Dirk

Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port

[Rob Landley]

On 08/02/2012 03:39 PM, Dirk Gouders wrote:
> Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de> writes:
> 
>> Rob Landley <rob@landley.net> writes:
>>
>>> On 07/29/2012 03:40 AM, Milton Miller wrote:
>>>> [adding Rob as Doc maintanier]
>>>>
>>>> On Sat, 28 Jul 2012 about 11:08:16 -0000, Dirk Gouders wrote:
>>>>> Borislav Petkov <bp@alien8.de> writes:
>>>>>
>>>>>> On Fri, Jul 27, 2012 at 11:24:53AM +0200, Dirk Gouders wrote:
>>>>>>> Cong Wang <xiyou.wangcong@gmail.com> writes:
>>>>>>>
>>>>>>>> On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders
>>>>>>>> <gouders@et.bocholt.fh-gelsenkirchen.de> wrote:
>>>>>>>>> Hi Jesse,
>>>>>>>>>
>>>>>>>>> I would like to ask you to check if the documentation of "nc" in
>>>>>>>>> netconsole.txt is still correct.  I tried two different netcat packages
>>>>>>>>> and both require "-p" to specify the listening port.  I am wondering if
>>>>>>>>> that changed after the use of "nc" has been documented.
>>>>>>>>
>>>>>>>> On Fedora 16, `nc -u -l <port number>` works fine.
>>>>>>>
>>>>>>> Thanks for checking that.
>>>>>>>
>>>>>>> If the information I found is correct, Fedora uses OpenBSD's nc
>>>>>>> codebase.  The two netcat packages I tested on a Gentoo system differ in
>>>>>>> requiring the -p switch for the port specification.
>>>>>>
>>>>>> So say exactly that in the doc: that the *BSD's version of nc doesn't
>>>>>> need the port number specified with '-p' and you're covered.
>>>>> OK, I tried that in the attached patch.
>>>>> I'm not sure if every exeption needs to/should be documented, though.
>>>>>
>>>>> >From 3cdeac3e814471053129145c5fa8391acb365fd8 Mon Sep 17 00:00:00 2001
>>>>> From: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
>>>>> Date: Sat, 28 Jul 2012 12:32:49 +0200
>>>>> Subject: [PATCH] netconsole.txt: non-BSD versions of nc(1) require '-p'
>>>>>  switch
>>>>>
>>>>> Gentoo for example uses non-BSD versions of nc(1) which require
>>>>> the '-p' switch to specify the listening port.
>>>>>
>>>>> ---
>>>>> Documentation/networking/netconsole.txt |    3 ++-
>>>>>  1 files changed, 2 insertions(+), 1 deletions(-)
>>>
>>> Did this ever resolve to a specific recommended patch? The one at the
>>> start of the thread:
>>>
>>>  http://lkml.indiana.edu/hypermail/linux/kernel/1207.3/01995.html
>>>
>>> Apparently isn't it...?
>>
>> Sorry for the delay.
>> I tested the situation on a few distributions and am still thinking
>> about a proper way to write it in a way without netconsole.txt becoming
>> a kind of "netcat.txt".
>>
>> I would be glad about comments to what I currently have -- also, because
>> I am not a native English speaker:
>>
>> ------------------------------------------------------------------------
>> The remote host can run syslogd or netcat to receive the kernel
>> messages.  On distributions using a BSD-based netcat version
>> (e.g. Fedora, openSUSE and Ubuntu) the listening port must be
>> specified without the -p switch:
>>
>> 'nc -u -l -p <port>' / 'nc -u -l <port>' or
>> 'netcat -u -l -p <port>' / 'netcat -u -l <port>'
>> ------------------------------------------------------------------------
>>
>> At the end, I also attach what I have noted during the tests with the
>> different distributions.
>>
>> Dirk
>>
>> ------------------------------------------------------------------------
>> Problem on systems where the gnu-netcat package provides a symbolic
>> link /usr/bin/nc -> /usr/bin/netcat:
>>
>> gnu-netcat requires -p to specify the local port but does not complain
>> if invoked as `nc -l -u <port>'; you need to use -v to see that it
>> does not do what you might expect:
>>
>> # nc -l -u 4444 -v
>> Warning: Inverse name lookup failed for `0.0.17.92'
>> ------------------------------------------------------------------------
>>
>> Distro		Package						needs -p
>> 		Command invocation
>> ========================================================================
>> Arch		gnu-netcat					yes
>> (Website	nc | netcat
>>  documentation)
>> 		openbsd-netcat					no
>> 		nc.openbsd
>> ------------------------------------------------------------------------
>> Debian-6.0.5	netcat-openbsd					no 
>> 		nc | netcat | nc.openbsd		   
>> 		                                   
>> 		netcat / netcat-traditional (preinstalled)	yes
>> 		nc | netcat
>> 		                                   
>> 		netcat6						yes
>> 		nc | netcat | nc6
>> ------------------------------------------------------------------------
>> Fedora-17	nc (preinstalled)				no
>> 		nc
>>
>> 		nc6
>> 		nc6						yes
>> ------------------------------------------------------------------------
>> Gentoo		gnu-netcat					yes
>> 		netcat
>>
>> 		netcat						yes
>> 		nc
>>
>> 		netcat6						yes
>> 		nc | nc6
>> ------------------------------------------------------------------------
>> OpenSUSE-12.1	netcat-openbsd					no
>> 		nc | netcat
>> ------------------------------------------------------------------------
>> Ubuntu-12.04	netcat-openbsd (preinstalled)			no 
>> Desktop		nc | netcat | nc.openbsd
>> 		                                   
>> 		netcat / netcat-traditional			yes
>> 		nc | netcat		   
>> 		                                   
>> 		netcat6						yes
>> 		nc | netcat | nc6
>> ------------------------------------------------------------------------
> 
> Here is a patch that also includes Jan's suggestion for socat(1).

Or you could use the bash built-in functionality of /dev/udp/host/port
with redirection. Or you can write a program to do it using the C API.

This seems about as silly as trying to document /proc/sys/vm/drop-caches
by listing the various ways you can write to a file.

Rob
-- 
GNU/Linux isn't: Linux=GPLv2, GNU=GPLv3+, they can't share code.
Either it's "mere aggregation", or a license violation.  Pick one.

Re: [RFC PATCH] netconsole.txt: "nc" needs "-p" to specify the listening port

[Jan Engelhardt]

On Friday 2012-07-27 08:35, Dirk Gouders wrote:
>diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt
>index 8d02207..ffe30a7 100644
>--- a/Documentation/networking/netconsole.txt
>+++ b/Documentation/networking/netconsole.txt
>@@ -52,7 +52,7 @@ initialized and attempts to bring up the supplied dev at the supplied
> address.
> 
> The remote host can run either 'netcat -u -l -p <port>',
>-'nc -l -u <port>' or syslogd.
>+'nc -l -u -p <port>' or syslogd.

While at it, could you add

  socat udp-recv:<port> -

since netcat is _really_ archaic ;-)