how to know who ping my computer ? [duplicate]

It looks like you're asking how to see who's pinging you, right? One quick and dirty way would be using tcpdump to simply monitor all incoming ICMP echo requests:

sudo tcpdump -i ethX icmp and icmp[icmptype]=icmp-echo

where ethX is the name of the adapter you're interested in listening to.

Note that tcpdump will resolve hostnames by default, so you might need to add the -n option to get IPs instead.

(This is, by the way, basically identical to the instructions given in the question you linked, though they are for Wireshark, a related but separate tool.)

You can use tcpdump like this

tcpdump ip proto \\icmp

and you get this kind of output

09:25:22.650727 IP 192.168.1.69 > centos6.lan: ICMP echo request, id 1, seq 1, l ength 40 09:25:22.650816 IP centos6.lan > 192.168.1.69: ICMP echo reply, id 1, seq 1, len gth 40

You could use iptables too

 iptables -I INPUT -p icmp --icmp-type 8 -m state  --state NEW,ESTABLISHED,RELATED -j LOG --log-level=1 --log-prefix "Ping Request "

and get messages like this in /var/log/messages (on CentOS at least)

Nov 14 09:43:35 centos6 kernel: Ping Request IN=eth0 OUT= MAC=00:0c:29:d2:2c:38:00:0c:29:fe:8e:bb:08:00 SRC=192.168.1.69 DST=192.168.254.188 LEN=60 TOS=0x00 PREC=0x00 TTL=126 ID=6551 PROTO=ICMP TYPE=8 CODE=0 ID=1 SEQ=37