Joseph L. Casale wrote:

I am trying to determine the root of an issue I am having. How can I watch traffic destined to a specific port on my CentOS 5.1

box to see if its even hitting it? It would be udp traffic.

Thanks! jlc

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CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos

If you're using IPTABLES on your CentOS box, then you can "watch" the traffic hit your rules using "watch -d iptables -nvL". The -d will highlight changes (so you can spot them) and you should see the number of packets change as each packet is processed by your rules.

If you have a specific chain name that deals with your port, then add that after the -nvL in the command - e.g. "watch -d iptables -nvL myChain"

Ian

On Tuesday 20 May 2008 8:57:08 Joseph L. Casale wrote:

I am trying to determine the root of an issue I am having. How can I watch traffic destined to a specific port on my CentOS 5.1 box to see if its even hitting it? It would be udp traffic.

Thanks! jlc

Try tcpdump -i <interface> udp port <port>.

-Chris

Joseph L. Casale wrote:

I am trying to determine the root of an issue I am having. How can I watch traffic destined to a specific port on my CentOS 5.1 box to see if its even hitting it? It would be udp traffic.

Use wireshark if you are logged in with a gui. In text mode use tcpdump. In either you can specify a filter with protocol, source and/or destination addresses and port number. Something like tcpdump -i eth0 udp might be enough if you don't have a lot of traffic or tcpdump -i eth0 udp and port portnumber to narrow it down more.