Why tcpdump don't work?
cswiger at mac.com
Fri Aug 29 05:27:03 UTC 2008
On Aug 28, 2008, at 10:03 PM, EdwardKing wrote:
> I have a server and a client,they use TCP to communication.For
> example,when client send a message to server,the server return the
> same message to client,then client show it.When client or server
> shutdown,it will send FIN.So I want to use tcpdump to watch it. The
> server and client in the same machine,the IP is 126.96.36.199 and the
> port is 9999
> [ ... ]
> when client and server communication or client shutdown,tcpdump
> don't show any message!
> Why? I am very puzzle with it! How to show server and client tcp
> communication information by using tcpdump?
If both client and server are running on the same machine, then the
network traffic doesn't actually go through your le0 network
interface-- instead, it uses the loopback interface, lo0, on IP
127.0.0.1. Try something more like:
tcpdump -i lo0 -v tcp port 9999
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