I pinged from dedicate server to my computer using ssh client.
It worked well, but ping from my computer to dedicate server is not working.
If anyone know what's the reason,please help me.
thanks.

check iptables -L or ipchains -L you distribution probably has a default firewall setup to block incoming ICMP (ping) requests

I checked iptables -L command.
It returned as follows;
Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

and before posting I cleared all content in file /etc/sysconfig/iptables and restarted iptables service.
the result I written above is blocking incoming icmp requests?
And I can't connect to remote mysql server.
help me.

There must be a firewall between your computer and the dedicated server that is blocking ICMP and MySQL traffic originating from your computer. Probably, this firewall is on the network run by the company hosting your dedicated service. A fast way to check would be to run tcpdump or wireshark from a shell on the dedicated server and see if the packets are even getting to it. My guess is that they're not due to the presence of an intervening firewall (as you've disabled yours). I'd check with the people that run the network that your dedicated server sits on.

thanks to btmiller and mindsport.
I am first using linux and dedicate server. So have many trouble.
I have two dedicated server. One is in panama and other is in usa.
these are all hosted by same hosting service.
panama server is working well pinging to my computer each other and I can read mysql data from server using mysqlfront.
but usa server is not that. what this means?

It means most likely that the datacenter network in the USA has a firewall blocking incoming ICMP and MySQL connections. Unless you have a firewall onyour own local network that from some reason is blocking these USA-bound packets, this is the best explanation I can think up. Once again, I reiterate that you need to contact your dedicated server provider to verify whether or not this is the case.

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