I am anadministrtor of a network.
My sever is a domain controller.My server can
ping one of my client and this client can ping my sever too.my client is belong to my domain.
My problem is that my server and my client can't see each other in my network and therefor They can't share any file for eah other.

Pinging just means that TCP/IP is set up and configured properly. In order to "see" each other in the network neighborhood, they both need to have File and Print Sharing Enabled, be members of the same domain or workgroup, and be on the same network. Also it takes time for computers to show up in a browse list so even after you have taken the above steps they may not show up instantly but should be visible in less than an hour. Browse list announcements are every 12 minutes and it can take up to 51 minutes for all the browse lists to be updated and all computers show up. Even when you shut down a computer, it will still appear in the browse list for up to 51 minutes after it was shut off again due to the timing of browse list announcements.

I join my client to the workgroup that was in my server.
when I doubleclick on "view workgroup computer"'s icon this message is become apparent : "workgroup is not accessible.You might not have permission to use this network resource.Contact the administrator of this server to find out if you have access permissions.The list of servers for this workgroup is not currently available."
Meanwhile I can see the client in my server's workgroup.
when I doubleclick on the client's name in workgroup's icon in my server this message is become apparent:"\\ the client is not accessible.The network path was not found."
please help me to solve this problem.
thank you.

what are the IP addresses and subnet mask that you gave to each of these computers?
Do both computers have the same username and password. For instance, if you are logging on as Administrator, is the password the same on both machines?