Mysql connections not closing with VB.NET application - mysql

Question

that's my first time here, I'm going mad because of this problem I have:
I'm developing a windows form application with VB.NET using multiple types of connections(mysql,odbc and SQL server) everything works fine until I get into MySQL..
MySQL server is a physical windows 7 pc, I connect to it through IPSEC VPN TUNNEL.
I need to perform 2 MySQL connections every x seconds, if I get some type of result after the first connection then I'll open the second one, and so on every x seconds(that's all wrote in my timer.tick event handler).
The problem is that quite often some connections on MySQL server keep staying alive(ESTABLISHED) on MySQL server and I can't find out why... code looks fine, there are both open and close methods declared at the right time, I've also tried Dispose,ClearPool and ClearAllPools methods but I keep having those connections up until I close my program or it reaches connection limit.
Here's the code:
Class connection:
Public Sub connMySQL()
Dim connstring As String
Try
If stabilimento = "1PR" Then
If cesoia = "" Then
connstring = "server=192.168.123.18;userid=xx;password=xx;database=xx;Connect Timeout=30"
Else
connstring = "server=192.168.123.253;userid=xx;password=xx;database=xx;Connect Timeout=30"
End If
End If
If stabilimento = "2PR" Then
If cesoia = "" Then
connstring = "server=192.168.1.18;userid=xx;password=xx;database=xx;Connect Timeout=30"
Else
connstring = "server=192.168.123.253;userid=root;password=xx;database=xx;Connect Timeout=30"
End If
End If
conMySql = New MySqlConnection(connstring)
If conMySql.State = ConnectionState.Closed Then
conMySql.Open()
End If
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Sub
Class where the iteration is performed:
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
connMySQL()
comm = New MySqlCommand("SELECT count_1,count_2,start_stop,data_ora,id FROM plc_contatori where plc_nome='" + plc_nome + "' and data_ora > '" + data_ieri.ToString("yyyy/MM/dd") + "' order by data_ora desc limit 1", conMySql)
dr = comm.ExecuteReader()
While (dr.Read())
count_1(0) = dr.GetValue(0)
start_stop(0) = dr.GetValue(2)
data_ora(0) = dr.GetValue(3)
If id <> dr.GetValue(4) And count_2(0) <> dr.GetValue(1) Then
id = dr.GetValue(4)
count_2(0) = dr.GetValue(1)
Else
Exit Sub
End If
End While
dr.Close()
dr.Dispose()
conMySql.Close()
conMySql.Dispose()
conMySql.ClearPool(conMySql)
conMySql.ClearAllPools()
If Not conMySql Is Nothing Then conMySql = Nothing
comm.Dispose()
If start_stop(0) = 1 Then
Exit Sub
End If
Dim dum_count_2 As Integer = count_2(0) - 1
connMySQL()
comm = New MySqlCommand("select count_1,count_2,start_stop,data_ora from plc_contatori where plc_nome='" + plc_nome + "' and data_ora > '" + data_ieri.ToString("yyyy/MM/dd") + "' AND count_2=" + dum_count_2.ToString + " ORDER BY data_ora desc limit 1", conMySql)
dr = comm.ExecuteReader()
While (dr.Read())
count_1(1) = dr.GetValue(0)
count_2(1) = dr.GetValue(1)
start_stop(1) = dr.GetValue(2)
data_ora(1) = dr.GetValue(3)
End While
dr.Close()
dr.Dispose()
conMySql.Close()
conMySql.Dispose()
conMySql.ClearPool(conMySql)
conMySql.ClearAllPools()
If Not conMySql Is Nothing Then conMySql = Nothing
comm.Dispose()
If count_1(0) = count_1(1) And start_stop(1) <> 1 And count_2(0) <> count_2(1) Then
'sub that reads some values from an odbc connection
CheckFermo()
End If
End Sub
NOTE that variables that I have not declared in this portion of code are declared in the public class of the form.
I'm wondering what could be wrong... maybe the 2nd connection is being established before the 1st one gets closed by the server?

Answer 1

I changed the connMySQL method to a function that returns the connection string. I have declared several variables so the code makes sense. I made several assumptions about datatypes. You may have to change this back to String and VarChar if these values are actually stored as strings. (I hope they are not)
You could use a single connection but all the assignments and comparisons would occur with an open connection.
Private stabilimento As String
Private cesoia As String
Public Function connMySQL() As String
Dim connstring As String
Select Case True
Case stabilimento = "1PR" And cesoia = ""
connstring = "server=192.168.123.18;userid=xx;password=xx;database=xx;Connect Timeout=30"
Case stabilimento = "2PR" And cesoia = ""
connstring = "server=192.168.1.18;userid=xx;password=xx;database=xx;Connect Timeout=30"
Case Else
connstring = "server=192.168.123.253;userid=root;password=xx;database=xx;Connect Timeout=30"
End Select
Return connstring
End Function
Private count_1(10) As Integer
Private count_2(10) As Integer
Private start_stop(10) As Integer
Private data_ora(10) As Date
Private id As Integer
Private plc_nome As String
Private data_ieri As Date
Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
Using dt As New DataTable
Using cn As New MySqlConnection(connMySQL),
comm = New MySqlCommand("SELECT count_1,count_2,start_stop,data_ora,id
FROM plc_contatori
where plc_nome= #plcNome and data_ora > #dataOra
order by data_ora desc
limit 1", cn)
comm.Parameters.Add("plcNome", MySqlDbType.VarChar).Value = plc_nome
comm.Parameters.Add("dataOra", MySqlDbType.Date).Value = data_ieri '.ToString("yyyy/MM/dd")
cn.Open()
Using dr = comm.ExecuteReader
dt.Load(dr)
End Using 'closes and disposes reader
End Using 'closes and dispose connection and command
count_1(0) = CInt(dt(0)(0))
start_stop(0) = CInt(dt(0)(2))
data_ora(0) = CDate(dt(0)(3))
If id <> CInt(dt(0)(4)) AndAlso count_2(0) <> CInt(dt(0)(1)) Then
id = CInt(dt(0)(4))
count_2(0) = CInt(dt(0)(1))
Else
Exit Sub
End If
End Using 'disposes DataTable
If start_stop(0) = 1 Then
Exit Sub
End If
Dim dum_count_2 As Integer = count_2(0) - 1
Using dt As New DataTable
Using cn As New MySqlConnection(connMySQL),
comm As New MySqlCommand("select count_1,count_2,start_stop,data_ora
from plc_contatori
where plc_nome= #plcNome
and data_ora > #dataOra
AND count_2= #count2
ORDER BY data_ora desc
limit 1", cn)
comm.Parameters.Add("#plcNome", MySqlDbType.VarChar).Value = plc_nome
comm.Parameters.Add("#dataOra", MySqlDbType.Date).Value = data_ieri '.ToString("yyyy/MM/dd")
comm.Parameters.Add("#count2", MySqlDbType.Int32).Value = dum_count_2 '.ToString
cn.Open()
Using dr = comm.ExecuteReader()
dt.Load(dr)
End Using
End Using
count_1(1) = CInt(dt(0)(0))
count_2(1) = CInt(dt(0)(1))
start_stop(1) = CInt(dt(0)(2))
data_ora(1) = CDate(dt(0)(3))
End Using
If count_1(0) = count_1(1) AndAlso start_stop(1) <> 1 AndAlso count_2(0) <> count_2(1) Then
'sub that reads some values from an odbc connection
CheckFermo()
End If
End Sub