This is an abstract method that is overridden in descendant classes.
TIdRexec and
TIdRSH override this will a function that calls an internal protected method called InternalExec passing the two authentication parameters required by the respective protocols. We do the coding this way because RSH uses the user's local User ID and the user's User ID on the remote host as part of it's authentication while Rexec requires the user's User ID on the remote machine and the password for authentication. Parameters:
ACommand - The command to execute on the remote system.