I compiled the mtsdemo.prg from the Internet Applications book and then did this:

build mtdll mtsserver from mtsserver
o = CreateObject('mtsserver.mtsdemo')
? o.slowhit(5)

And I got this error:

OLE IDispatch exception code 924 from mtsserver.MTSDemo msserver.MTSDemo: .slowhit e:\eb\mtscom\mtsdemo.prg Error in line 44 LOCONTEXT is not an object. 924..

Where line 44 in the code is:

35 FUNCTION SlowHit
36 LPARAMETER lnSecs
37 LOCAL loMTS, loContext, x
38 
39 THIS.Writeoutput("SlowHit Fired" + TRANSFORM(lnSecs))
40 loContext = THIS.oMTS.GetObjectContext()
41 
42 lnSecs=IIF(EMPTY(lnSecs),0,lnSecs)
43 
44 If loContext.IsCallerInRole("BookReader")
45    THIS.WriteOutput("Caller is in role")
46 ENDIF   
47 
48 
49 DECLARE Sleep IN WIN32API INTEGER
50 for x=1 to lnSecs
51   FOR x=1 to lnSecs
52     Sleep(1000)
53   ENDFOR
54 ENDFOR
...