winsock data arrival

I made a program that communicate with some electronic device using winsock udp protocol, i am trying to write a function that will tell me rather or not a device is online by looking at if anything is sent back from the device.

this is my function
Private Sub Winsock1_DataArrival(ByVal bytesTotal As Long)

Dim strData As String

Winsock1.GetData strData, vbString, bytesTotal

If Not Len(strData) = 0 Then
online = 1
End If

End Sub

i declared the variable "online" as a global variable, but somehow "online" is always 0...i think i am trying to do this the wrong way, can anyone give me a hand?

Have you checked whether the data actually arrives? Does your strData contain anything?

yes data does arrive, strdata is the string i receive from my devices.

Try setting a breakpoint somewhere in this sub. I get the feeling that it gets called several times.

a break point you mean using the sleep function? yes the function will get call several times since i am trying to test connection with around 5-6 devices :sick:

Why sleep? Just press F9 at the needed line of code and the program will stop executing at this very point (you can continue it from this place rather than restart it).

You can count how many times your sub gets called.

This code:

vb.net Code:

If Not Len(strData) = 0 Then
    online = 1
End If

provides that your sub sets the online variable to 1
if it somehow reverts to 0 then your global variable is modified somewhere else.

A little advice - change your sub into function:

vb.net Code:

Private Function IsOnline(ByVal bytesTotal As Long) As Boolean
    Dim strData As String
    Winsock1.GetData strData, vbString, bytesTotal
    If strData.Length > 0 Then Return True Else Return False
End If

Then you can simply call it:

If Online(your args) Then ...

unfortunately i cannot modify the sub function because it is associated with the winsock property, i tried changing the data_arrival function to return a value, it will give me an error

in my main function i have this

Do Until (allocate_rs.EOF)
ID = allocate_rs.Fields("Cont_IP").Value
Call check_online
allocate_rs.MoveNext
MsgBox online
Loop

i tried using your suggestion in the sub function

If Not Len(strData) = 0 Then
online = 1
End If

but everytime "online" is displayed as blank (no value)

This code will always set Online = 1 if your strData is not empty.

Code:

---

If Not Len(strData) = 0 Then
    online = 1
End If

---

ALWAYS!

Either your 'online' variable is modified elsewhere (you don't use multithreading here, do you?) or your strData is empty. There are no other options. You say you've checked and strData is not empty then we only have one remaining option: your global variable called 'online' is modified elsewhere

vb.net Code:

By the way, you could shadow your online variable by some local one with the same name.
 
Module GlobalModule
   Public Online As Integer = 1 ' Global variable
 
   Public Sub Main
         MsgBox(Online) ' Will return 1
         Call SomeSub()
         MsgBox(Online) ' Will return 1
   End Sub
 
   Public Sub SomeSub()
         Dim Online As Integer  ' You shadow the global one
         MsgBox(Online)  ' Will return 0
   End Sub
End Module

i think i find out the problem now...is not about my code (or maybe it is), i realized that when i do a loop to send data

Do Until (read_controller_rs.EOF)
send = "02000BFFFFFFFFFFFF113100FFD403"
Winsock1.SendData send
read_controller_rs.MoveNext
Loop

my data arrival will only be fired AFTER the loop goes through, so it means that if i have 4 senddata, i will not receive anything until all data has been sent then my data arrival will fire and i get all 4 replys at once.

I am still pretty confuse about why it work this way, i want to get a respond everytime i sent data but instead i get 4 responds back after i send all 4 data....:confused:

Not a perfect solution but...

vb.net Code:

Do Until(read_controller_rs.EOF)
    For each c As Char In send
       Winsock1.SendData c
    Next
    read_controller_rs.MoveNext
Loop