tcpdump giving error

[ypeksen]

Hello all,

I run a ns3 program. and .pcap (packet capture) files were generated.
When I execute the command "tcpdump -r ....0-0.pcap -nn -tt" to check
whether the result of it is as expected, I get this error:

tcpdump: truncated dump file; tried to read 4 file header bytes, only
got 0

I have no idea how to solve it. I searched for the problem in the
forum and googled it but did not find anything. Is something wrong or
missing in the program?

ypeksen

[halil yetcom]

Maybe you need root Privilege to run Tcpdump. Try it.

2011/3/14 ypeksen <yavuzpe...@gmail.com>

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University of Southampton
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[Lalith Suresh]

Hello,

Check the size of the pcap files. Your simulation probably generated blank files because no data was exchanged.

 

ypeksen

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[ypeksen]

Sorry for the late response. I have been deeply working on my
program.

@Halil Yetcom;
I tried it with root privilege but I got this; tcpdump: wifi-simple-
adhoc-grid-0-0.pcap: Permission denied. By the way,my name is Yavuz :)
happy to see you around..

and then,

@Lalith Suresh;
You were right, It generated blank files but i did not understand why
it did. What might be the cause of this? Since I saw that packets were
flowing from a node to another node. during the simulation with
visualization tool. Thank you for the progress...

ypeksen,

On Mar 14, 10:42 pm, Lalith Suresh <suresh.lal...@gmail.com> wrote:
> Hello,
>

> *Instituto Superior Técnico*www.lalith.in

[Lalith Suresh]

Hello,

On Tue, Mar 15, 2011 at 11:48 AM, ypeksen <yavuzpe...@gmail.com> wrote:

@Lalith Suresh;
You were right, It generated blank files but i did not understand why
it did. What might be the cause of this? Since I saw that packets were
flowing from a node to another node. during the simulation with
visualization tool. Thank you for the progress...

Have you enabled PCAP tracing on the right NetDevice helper and/or the right nodes?

 

--
Lalith Suresh

Department of Computer Science and Engineering

Instituto Superior Técnico
www.lalith.in

[B Brian]

One thing to try might be to specifically set the interface you are capturing from.

List all the available interfaces.

tcpdump -D 

It should numerically list your interfaces.

Then when capturing it may require you to specify which interface to capture from.

tcpdump -i 1,2,3 etc

Not sure if this helps however it was my first thought when you mentioned 0 captures and a file with nothing in it.