The Task list provided lists all the PxPlus tasks on the server and since they are running on the server they will all technically have the same NID as the process issuing the TSK(*PROCESS LIST)
In theory if you are using WindX your application could have change the NID value to that of the WindX workstation. If you are using Simple CS it saves the true workstation NID on a file tied back to the process ID thus you can see whose workstation is actually connected by simply entering the command "KILL" which normally is used to kill processes but does provide an easy way to see which workstations are on.