Enter-Pssession not working

I have to machines in same network one with windows7 and another win windows server 2012.I tried Enter-PSsession on windows7 machine from server2012 machine...

       $ComputerName = "windows7-PC"       $username="administrator"       $password="password"       $secstr = New-Object -TypeName System.Security.SecureString       $password.ToCharArray() | ForEach-Object {$secstr.AppendChar($_)}       $cr = new-object -typename System.Management.Automation.PSCredential -argumentlist $username, $secstr       $Session = New-PSSession -ComputerName $ComputerName -Credential $cr        Invoke-Command -Session $Session -ScriptBlock { echo '1' }

On doing same,i got an error

      New-PSSession : [windows7-PC] Connecting to remote server windows7-PC failed with the following error message : Access is denied.      Invoke-Command : Cannot validate argument on parameter 'Session'. The argument is null or empty. Provide an 

argument that is not null or empty, and then try the command again.

using same script i m able to execute 'echo 1' from windows7-pc to server2012-pc but not from server2012-pc to windows7-pc.