Determine the host on which the message server is running by looking at the profile /usr/sap/<SAPSID>/SYS/profile/DEFAULT.PFL under the parameter rdisp/mshost. This parameter indicates which host the message server is running on.
Log on to the host where the message server is running at operating system level as user <sapsid>adm.
To determine the 11 character hardware key for the server, enter the command saplikey pf=<profile> -get.