mutex - VB6: Single-instance application across all user sessions -

-

i have application needs single-instance app across user sessions on windows pc. research far has centered around using mutex accomplish this, having issue not sure issue, best-practice question believe.

here's code first of all:

private const appver = "global\uniquename" ' not using name unique  public sub main()      dim mutexvalue long      mutexvalue = createmutex(byval 0&, 1, appver)     if (err.lastdllerror = error_already_exists)         savetitle$ = app.title         app.title = "... duplicate instance."         msgbox "a duplicate instance of program exists."         closehandle mutexvalue         exit sub     end if     ' else keep on truckin'

now, based on this article believe understand passing null pointer createmutex function above i'm assigning whatever security descriptor associated logged in user.

if means think (i may need more guidance here) tells me other users log in not able "see" mutex created under original user's session, nor able create mutex same name.

now, emperical evidence seems up. used message box pop "lastdllerror" receiving, , when user attempted launch application (while running under user account) receive error_access_denied code. ok testing against along error_already_exists code , exiting on either/or. however, feels sort of hackish , i'm wondering if can suggest alternative. "right" thing seems to pass proper pointer createmutex function such user has proper permissions view existing mutexes (mutices?), i'm not sure possible without logged in user being admin (which unacceptible). assistance/guidance appreciated. in advance!

i looking similar solution in vb6 late last year. @ time unable find examples of vb6 apps communicating across user boundary, had write own.

see: interprocess communication via semaphores

you can use class create , check global semaphore tell if app running under user. didn't @ mutex apis usage similar. getsecuritydescriptor function you'll want transpose if you've got mutex code written.


Comments

Post a Comment

Popular posts from this blog

java - SNMP4J General Variable Binding Error -

-
i trying use snmp4j snmp bulkget. when ever use snmp4j make call returned responseevent error says "general variable binding error" , data returned equal null. to debug: print out, console, exact oid , version number using in snmp4j. use printed out data snmpwalk on command line. valid results. know sending snmp4j correct pdu correct oid, version number, max repititions, etc. i have used snmp4j , code wrote succesffuly monitor other devices years. don't know different time. leaving me stumped. why "general variable binding error?" causes error? ideas debug? can reproduced? if so, first action should using wireshark or microsoft network monitor capture network packets. my guess agent gives generr response, not surprising, http://www.ietf.org/rfc/rfc1157.txt
Read more

windows - Python Service Installation - "Could not find PythonClass entry" -

-
i working on building python service. inducing error, not sure inducing it. ps c:\...> python .\file.py debug debugging service myservice - press ctrl+c stop. error 0xc00000f4 - not find service's pythonclass entry in registry error 1814 - specified resource name cannot found in image file. error 0xc0000080 - not locate module name in python class string (ie, no '.') this error coming pythonservicemessages.mc in pythonwin32. it turns out error result caused exception being thrown , python script dying off.
Read more

Determine if a XmlNode is empty or null in C#? -

-
the following code takes xmlnode data type , populates dataset object xmlnode content. write dataset's content file. public void populatedataset(xmlnode node) { xmlnodereader reader = new xmlnodereader(node); dataset ds = new dataset(); ds.readxml(reader); system.guid guid = system.guid.newguid(); string name = string.format("{0}{1}_{2}.xml", utility.xmloutputpath, utility.xmloutputfilename, guid.tostring()); //need write "node empty" file if xmlnode object empty of null ds.writexml(name, xmlwritemode.ignoreschema); } the problem encountered 1 scenario not write content file. how determine if xmlnode object null or empty? you can check if node parameter null or has innertext or innerxml properties null or empty, when enter method before creating xmlnodereader .
Read more