vb.net - Multi-Threading IP Address Pings Causing Application Crash -
boy, learning new can real headache if can't find solid source. have been designing applications in linear fashion time , want step more powerful approach. have been reading on threading, , perhaps have gone larger level should. however, 1 steps when application calls , no better time present learn new.
my program designed seems rather simple, has become extremely difficult create in smooth running manor. original design created object of each device on network wished ping, in real world environment kindles. goal ensure still connected network pining them. used for loop , obj array set on timer. had unexpected results causing listview flicker , load after listview1.items.clear. evolved updating list items rather clearing them , flicker remained.
i assumed due slow process of array , pings started hunting solutions , came across multi-threading. have known time, have yet dive practice. program seemed need more speed , smoother operation took stab @ it. below code in complete form result, crashes , throws errors. have not used threading intended. using in simpler functions works fine , feel have grasp. if want program pointlessly run counters.
i don't know next in steps getting task done, , figure combining several different methods mush of dead program. use getting on track this. comments welcome , thank checking out code.
form1 code
public class form1 'obj array public shared objdevice new list(of kdevice) 'thread array each obj public shared thread() system.threading.thread private sub iprefresh(objid, itempos) dim objdev kdevice = objid if my.computer.network.ping(objdev.kip) objdev.kstatus = "online" objdev.kpings = 0 else objdev.kpings += 1 end if if objdev.kpings >= 8 objdev.kstatus = "offline" objdev.kpings = 0 listview1.items(itempos).backcolor = color.red end if dim str(4) string dim itm listviewitem str(0) = objdev.kname str(1) = objdev.kip str(2) = objdev.kstatus str(3) = objdev.kpings itm = new listviewitem(str) listview1.items(itempos) = itm end sub private sub form1_load(sender object, e eventargs) handles mybase.load me.checkforillegalcrossthreadcalls = false ' adding listview columns listview1.columns.add("device", 100, horizontalalignment.left) listview1.columns.add("ip address", 150, horizontalalignment.left) listview1.columns.add("status", 60, horizontalalignment.left) listview1.columns.add("pings", 60, horizontalalignment.left) dim iplist new list(of string) dim namelist new list(of string) using myreader new microsoft.visualbasic.fileio.textfieldparser("kdevices.csv") myreader.textfieldtype = microsoft.visualbasic.fileio.fieldtype.delimited myreader.delimiters = new string() {","} dim currentrow string() dim rowp integer = 1 while not myreader.endofdata try currentrow = myreader.readfields() dim cellp integer = 0 dim ntemp string = "" each currentfield string in currentrow select case cellp case 0 namelist.add(currentfield.replace("""", "")) case 1 iplist.add(currentfield.replace("""", "")) end select cellp += 1 next catch ex microsoft.visualbasic.fileio.malformedlineexception msgbox("line " & ex.message & " invalid. skipping") end try rowp += 1 end while end using dim namelar string() = namelist.toarray dim iplar string() = iplist.toarray redim preserve thread(namelar.length) integer = 0 namelar.length - 1 dim newdevice new kdevice dim objnum = objdevice.add(newdevice) newdevice.kname = namelar(i) newdevice.kip = iplar(i) if my.computer.network.ping(newdevice.kip) newdevice.kstatus = "online" else newdevice.kstatus = "loading" end if dim str(4) string dim itm listviewitem str(0) = newdevice.kname str(1) = newdevice.kip str(2) = newdevice.kstatus str(3) = newdevice.kpings itm = new listviewitem(str) if newdevice.kstatus = "loading" itm.backcolor = color.yellow end if listview1.items.add(itm) thread(objnum) = new system.threading.thread(sub() me.iprefresh(objdevice(objnum), objnum)) next end sub private sub timer1_tick(sender object, e eventargs) handles timer1.tick integer = 0 objdevice.count - 1 thread(i).start() next end sub end class kdevice class
public class kdevice private strkname string private strkip string private strkstatus string private strklaststatus string private strkpings integer = 0 public property kname string return strkname end set(value string) strkname = value end set end property public property kip string return strkip end set(value string) strkip = value end set end property public property kstatus string return strkstatus end set(value string) strkstatus = value end set end property public property kpings integer return strkpings end set(value integer) strkpings = value end set end property end class the error / crash on line 32 of code when tries pass update listview item
an unhandled exception of type 'system.argumentexception' occurred in microsoft.visualbasic.dll additional information: invalidargument=value of '18' not valid 'index'. or
an unhandled exception of type 'system.nullreferenceexception' occurred in microsoft.visualbasic.dll additional information: object reference not set instance of object. if code not make sense, or @ lease idea of trying make do, please let me know , explain whichever parts unclear. again thank looking on issue.
just possible issue noticed:
dim str(4) string dim itm listviewitem str(0) = newdevice.kname str(1) = newdevice.kip str(2) = newdevice.kstatus str(3) = newdevice.kpings itm = new listviewitem(str) if newdevice.kstatus = "loading" itm.backcolor = color.yellow end if listview1.items.add(itm) in bit here, declare str(4) 5 possible indexes (remember starts @ zero), should have 4 (str(3)) . don't think whole issue, small bit should fix. may want other ways update listview without setting
me.checkforillegalcrossthreadcalls = false here's awesome guide helped me when did first multi threaded application: http://checktechno.blogspot.com/2012/11/multi-thread-for-newbies.html
Comments
Post a Comment