Socket reconnection problem 2

[bminaeff]

I have an application where a program sends some data out a socket to a barcode printer. It works fine until they kill the power to the printer. After this happens I can not seem to reconnect automatically. How would I know that they have turned the power off or how can it automatically reconnect?

This is just my example to work with and works off a button click and a textbox

Thanks,
Bill M

Imports System.Net.Sockets
Imports System.Text
Public Class Form1
    Dim printerconnection As New System.Net.Sockets.TcpClient()

    Function FormatBarcode(ByVal input As String) As String
        Dim mystring As String
        Dim humanreadable As String = input.Insert(6, " ")
        Dim start As Char = Convert.ToChar(2)
        Dim es As Char = Convert.ToChar(27)
        Dim done As Char = Convert.ToChar(3)
        mystring = start & es & "A" & es & "%3" & es & "H0700" & es & "V0300" & es & "BG06400>I>F" & input & es & "H0300" & es & "V0075" & es & "$A,225,225,0" & es & "$=" & humanreadable & es & "Z" & done
        FormatBarcode = mystring
    End Function
    Private Sub Print_Barcode(ByVal input As String)
        Try
            Dim sendbytes As [Byte]() = Encoding.ASCII.GetBytes(input)
            Dim printersend As NetworkStream = printerconnection.GetStream()
If printerconnection.Connected = False Then
                printerconnection.Connect("10.0.0.2", 9100)
            End If
            If printersend.CanWrite = True Then
                printersend.Write(sendbytes, 0, sendbytes.Length)
            Else
                MessageBox.Show("Connection Lost", "Connection")
            End If
        Catch ex As Exception
            messagebox.show(ex.Message, "Error")
        End Try
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Try
            Dim input As String = TextBox1.Text
            input = FormatBarcode(input)
            Print_Barcode(input)
        Catch ex As Exception
            MessageBox.Show(ex.Message, "Error in Button")
        End Try

    End Sub

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Try
            printerconnection.Connect("10.0.0.2", 9100)
        Catch ex As Exception
            MessageBox.Show(ex.Message.ToString)
        End Try

    End Sub
End Class

 

[Sorwen]

It has been awhile since I messed with sockets, but if I remember there is a command to check if the connection is still active. When it is false (no longer active) and it shouldn't be false I would then have it start a timer that check every X seconds and try to reconnect. It would be best to still limit how may time it tried to reconnect.

-I hate Microsoft!
-Forever and always forward.

 

[bminaeff]

You wouldn't happen to be talking about the instance.connected property would you? I tried this but it didn't seem to make any difference.

 

[Sorwen]

I looked at my code and made myself a little more familiar with sockets again. Yes, it was the connected. What happens when you step through the code after the printer comes back up? Is the printerconnection true? Also no matter what you do you also want to move the printerconnection.connected check before your printerconnection.GetStream() you wanted to check the connection before you try to use it.

-I hate Microsoft!
-Forever and always forward.

 

[bminaeff]

This code will load and begin printing fine. When I cycle power to the printer it gives me the following exception:
"No connection could be made because the target machine actively refused it". Now if I click "OK" on the messagebox and try again it prints fine.

My other issue is that this printer is connected to an applicator machine, which means I have to have this data sent in a specific amount of time.

Thanks
-Bill

  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim input As String = TextBox1.Text
        Dim printerconnection As New System.Net.Sockets.TcpClient()

        Try
            printerconnection.Connect("10.0.0.2", 9100) ' Errors out here. Connection is refused or takes too long. 
            Dim barcode As String
            barcode = FormatBarcode(input)
            If printerconnection.Connected = False Then
                MessageBox.Show("Connection was lost")
            End If
            Dim sendbytes As [Byte]() = Encoding.ASCII.GetBytes(barcode)
            Dim printersend As NetworkStream = printerconnection.GetStream()
            'printersend.WriteTimeout = 1
            printersend.Write(sendbytes, 0, sendbytes.Length)
            printerconnection.Close()
        Catch ex As Exception
          
            MessageBox.Show(ex.Message, "Error in Button")
            ' End If
        End Try

    End Sub

 

[Sorwen]

Hmmm. Not sure. Working from this last piece of code so if you've pressed the button once then the printer is shut off you then bring the printer back up and press the button again it will fail on the connect line? If that is a yes then you could try messing with the connections timeout: printerconnection.SendTimeout = (time in milliseconds)

-I hate Microsoft!
-Forever and always forward.

 

[bminaeff]

If I run this piece of code and press the button it prints a label. I then turn the printer off wait about 10 seconds and turn it back on. Then I try to print another label. It fails on the connect line.

I will try to extend the timeout, but this code will eventually be used in a process that needs to be done in a fixed amount of time.

I think maybe the best idea is to possibly ping it on a timer and notice when the printer it turned off, but I am not sure how I would do this.

 

[bminaeff]

Sorwen or anyone,

Would it be possible to publicly declare printerconnection as a TcpClient, and connect to it on the form load. Then on a timer ping it and when I do not get a response dispose of this instance and ReDim the connection and connect it again when I get a response?

I tried to do this, but I am not very good with arrays and the ReDim statement. Here is what I tried, but it says that "Object reference not set to an instance of an object" on the if statement checking the connection status.

I havent put in the timer code yet but it would be a simple ping and if I get no response, disconnect and once I get a response and I am not connected, connect again.

-Thanks

Public Class Form1
    Dim printerconnection(0) As System.Net.Sockets.TcpClient


    Function FormatBarcode(ByVal input As String) As String
        Dim mystring As String
        Dim humanreadable As String = input.Insert(6, " ")
        Dim start As Char = Convert.ToChar(2)
        Dim es As Char = Convert.ToChar(27)
        Dim done As Char = Convert.ToChar(3)
        mystring = start & es & "A" & es & "%3" & es & "H0700" & es & "V0300" & es & "BG06400>I>F" & input & es & "H0300" & es & "V0075" & es & "$A,225,225,0" & es & "$=" & humanreadable & es & "Z" & done
        FormatBarcode = mystring
    End Function

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim input As String = TextBox1.Text

        Try
            Dim barcode As String
            barcode = FormatBarcode(input)
            If printerconnection(0).Connected = False Then
                MessageBox.Show("Connection was lost")
            End If
            Dim sendbytes As [Byte]() = Encoding.ASCII.GetBytes(barcode)
            Dim printersend As NetworkStream = printerconnection(0).GetStream()
            'printersend.WriteTimeout = 1
            printersend.Write(sendbytes, 0, sendbytes.Length)
            'printerconnection.Close()
        Catch ex As Exception

            MessageBox.Show(ex.Message, "Error in Button")
            ' End If
        End Try

    End Sub

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        ConnectToPrinter()
    End Sub
    Private Sub ConnectToPrinter()
        Try
            printerconnection(0).Connect("10.0.0.2", 9100) 
        Catch ex As Exception
        End Try
    End Sub
    Private Sub DisconnectFromPrinter()
        Try
            printerconnection(0).Close()
            ReDim printerconnection(0)
        Catch ex As Exception
        End Try
    End Sub
End Class

 

[earthandfire]

I don't have any way to test this, so I've just taken a couple of lines out of context.

replace:
Dim printerconnection(0) As System.Net.Sockets.TcpClient
with:
Dim printerconnection As System.Net.Sockets.TcpClient

and

precede this:
printerconnection(0).Connect("10.0.0.2", 9100)
with:
printerconnection = new System.Net.Sockets.TcpClient


at the appropriate places.

I don't see why you need an array.


Hope this helps.

 

[earthandfire]

precede this:
printerconnection(0).Connect("10.0.0.2", 9100)
with:
printerconnection = new System.Net.Sockets.TcpClient


should have been...
replace:
printerconnection(0).Connect("10.0.0.2", 9100)
with:
printerconnection = new System.Net.Sockets.TcpClient
printerconnection.Connect("10.0.0.2", 9100)


sorry about that.

 

[bminaeff]

Thats what I originally had, but then the ReDim statement requires a parenthesized list of the new bounds of each dimension of the array. Unless I am misusing the ReDim statement and there is a better (proper) way of creating a new instance of a public TcpClient.

 

[earthandfire]

Your original was:
Dim printerconnection As New System.Net.Sockets.TcpClient()


I'm suggesting that you change that to:
Dim printerconnection As System.Net.Sockets.TcpClient()

and use New at the point at which you create the connection. That way, if you lose it, you can use New again, perhaps in the Catch block.

Unfortunately, I am unable to test this, but I have successfully used similar logic with other types of objects in the past.

 

[earthandfire]

I'm too quick pressing Submit!!

ReDim allows you to change the "dimensions" of an existing (undimensioned) array, but you don't need an array of printer connections.

 

[earthandfire]

A simple, but crude example of what I mean:

The form has an empty TreeView control and a Button

Public Class Form1

    Dim tn As TreeNode                                          'declare the node object

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Try
            MessageBox.Show(TreeView1.Nodes(9).Text.ToString)   'will generate an exception until the 10th node exists
        Catch ex As Exception
            MessageBox.Show("The 10th TreeNode does not yet exist")
            tn = New TreeNode(TreeView1.Nodes.Count.ToString)   'create a new instance of the node declared above
            TreeView1.Nodes.Add(tn)
        End Try


    End Sub
End Class

 

[bminaeff]

Earthandfire,

Here is my code as I believe you have suggested. Whenever I try to print it says that "Object Reference not set to an instance of an object" This occurs in the button click and on my timer with the ping. Sorry to keep asking, but this is killing me.

Public Class Form1
    Dim printerconnection As System.Net.Sockets.TcpClient


    Function FormatBarcode(ByVal input As String) As String
        Dim mystring As String
        Dim humanreadable As String = input.Insert(6, " ")
        Dim start As Char = Convert.ToChar(2)
        Dim es As Char = Convert.ToChar(27)
        Dim done As Char = Convert.ToChar(3)
        mystring = start & es & "A" & es & "%3" & es & "H0700" & es & "V0300" & es & "BG06400>I>F" & input & es & "H0300" & es & "V0075" & es & "$A,225,225,0" & es & "$=" & humanreadable & es & "Z" & done
        FormatBarcode = mystring
    End Function

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim input As String = TextBox1.Text

        Try
            Dim barcode As String
            barcode = FormatBarcode(input)
            If printerconnection.Connected = False Then
                MessageBox.Show("Connection was lost")
            End If
            Dim sendbytes As [Byte]() = Encoding.ASCII.GetBytes(barcode)
            Dim printersend As NetworkStream = printerconnection.GetStream()
            'printersend.WriteTimeout = 1
            printersend.Write(sendbytes, 0, sendbytes.Length)
            'printerconnection.Close()
        Catch ex As Exception

            MessageBox.Show(ex.Message, "Error in Button")
            ' End If
        End Try

    End Sub

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        ConnectToPrinter()
    End Sub
    Private Sub ConnectToPrinter()
        Try
            Dim printerconnection As New System.Net.Sockets.TcpClient
            printerconnection.Connect("10.0.0.2", 9100) ' Errors out here. Connection is refused or takes too long. 
        Catch ex As Exception
        Finally

        End Try
    End Sub
    Private Sub DisconnectFromPrinter()
        Try
            printerconnection.Close()
        Catch ex As Exception

        End Try
    End Sub

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        Try
            Dim response As Boolean
            response = My.Computer.Network.Ping("10.0.0.2")
            If response = False Then
                DisconnectFromPrinter()
            Else
                If printerconnection.Connected = False Or printerconnection Is Nothing Then
                    ConnectToPrinter()
                End If
            End If
        Catch ex As Exception
            ' MessageBox.Show(ex.Message)
        End Try

    End Sub
End Class

 

[Sorwen]

This:

 Private Sub ConnectToPrinter()
        Try
            Dim printerconnection As New System.Net.Sockets.TcpClient
            printerconnection.Connect("10.0.0.2", 9100) ' Errors out here. Connection is refused or takes too long. 
        Catch ex As Exception
        Finally

        End Try
    End Sub

Needs to be changed to this:

 Private Sub ConnectToPrinter()
        printerconnection = New System.Net.Sockets.TcpClient

        Try
            printerconnection.Connect("10.0.0.2", 9100) ' Errors out here. Connection is refused or takes too long. 
        Catch ex As Exception
            'Add error handling.
        End Try
    End Sub

-I hate Microsoft!
-Forever and always forward.

 

[earthandfire]

Try this:

    Dim printerconnection As System.Net.Sockets.TcpClient

    Private Sub ConnectToPrinter()
        Try
            [s]Dim[/s] printerconnection [s]As[/s] [b]=[/b] New System.Net.Sockets.TcpClient
            printerconnection.Connect("10.0.0.2", 9100) ' Errors out here. Connection is refused or takes too long. 
        Catch ex As Exception
        Finally

        End Try

In your version you have two different printerconnection variables, the Form version declared at the top, and the local version declared in the ConnectToPrinter sub - however this is the one that you instanciate, but it goes out of scope as soon as the sub ends.

 

[bminaeff]

Sorwen and Earthandfire,

If you would both like, send me your addresses because you both get 5000 gold stars. Works like a charm. You guys are great, thanks alot for the help and patience.

 

[earthandfire]

Glad to be of help & thanks for the star.