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Using TurboFloat with Visual Basic .NET

VB.NETThis article will give step-by-step instructions on how to add floating-licensing to your VB.NET app. There's also a full example app (one Windows Forms example and one WPF example) that you can download and play with without needing to add licensing to your app.

By the end of this article you'll have working floating-licensing integrated with your application, and thus the ability to sell individual copies of your software.

This article shows you how to add floating-licensing to your VB.NET app using TurboFloat. To add hardware-locked licensing to your VB.NET app see the "Using TurboActivate with VB.NET" article.

Sign up or login and download the native TurboFloat library

Before you can do anything, you need to login to your LimeLM account (or sign up). Then download TurboFloat for Windows on your API page. That file contains the TurboFloat.dll with source code for a complete VB.NET example app (in the "API\VB.NET" directory).

Adding floating licensing to your appTurboActivate.dat and Version GUID

After you've created a new product, go to the version page of the product you will be adding licensing to. You will need to do 2 things:

  1. Download the TurboActivate.dat file for the product version.
  2. Make a note of the Version GUID.

You'll be including the TurboActivate.dat file in the same folder as the TurboFloat.dll file and you'll use the Version GUID in your code as part of integrating TurboFloat within your app.

Set the "Target CPU" (AnyCPU, x86, x64)

For VB.NET projects we recommend you set the "Target CPU" to x86. If you do this, your app will be able to run on both 32-bit and 64-bit machines without having to do complex installation scripts.

To set the target CPU to x86 first click the "Project -> [Project Name] Properties" menu in Visual Studio. Click the "Compile" tab on the right hand side. Click the "Advanced Compile Options..." button. Then choose x86 from the "Target CPU" dropdown:

Target CPU x86

Make sure you set this for both your "Release" and "Debug" configurations.

AnyCPU "Target CPU"

If instead of the x86 "Target CPU" you would rather choose AnyCPU then you need to make a few changes. The first thing you need to do add a "custom constant" TF_BOTH_DLL=TRUE (do this for both Debug and Release builds). Then you need to include both the x86 and x64 versions of TurboFloat with your binaries. So copy the TurboFloat.dll from the x86 folder and put it in the Debug & Release folders. In the x64 folder rename TurboFloat.dll to "TurboFloat64.dll".

Example project

Included in TurboFloat Library package is a simple example project. The TurboFloat.vb file contains all the functions you'll be using to add the floating licenses functionality to your app.

Step-by-step walkthrough

We're going to walk you through adding floating licensing to your app by using our VB.NET example application. If you haven't downloaded it already you can get the example app inside the TurboFloat Library package.

Step 1. Start the TurboFloat Server

Before you can continue, you need to start a TurboFloat Server instance. We recommend spinning-up a TurboFloat Server instance on our infrastructure using LicenseChest. Alternatively, your customers can host the TurboFloat Server on their own infrastructure by activating and installing the TurboFloat Server locally.

We recommend using our hosted TurboFloat Server option because it's fast, stable, up-to-date, and incredibly easy to deploy.

Step 2. Request "license lease"

In the example "Text Editor" VB.NET application the "Form1.vb" file is the main UI for the app. That is, it's the entry point for the application. And because it's the entry point of the application it's where we'll be requesting the "license lease" from the TurboFloat Server.

First, create the TurboFloat instance as a private member in the class:

Public Class Form1

    Private ReadOnly tf As TurboFloat
    Dim frmLeaseExp As LeaseExpired = Nothing

Then, in the constructor for the form, you'll actually create the new instance of the TurboFloat class. Paste the Version GUID you copied from earlier:

Public Sub New()

        'TODO: goto the version page at LimeLM and paste this GUID here
        tf = New TurboFloat("PASTE-VERSION-GUID-HERE")

    Catch ex As TurboFloatException
        MessageBox.Show("Failed to get a lease from the floating license server: " & ex.Message)
        Exit Sub
    End Try

End Sub

Next, we'll actually request the lease from the TurboFloat Server:

    'TODO: goto the version page at LimeLM and paste this GUID here
    tf = New TurboFloat("PASTE-VERSION-GUID-HERE")


Step 3. Handle the "LeaseChange" event

The native TurboFloat library handles all the details about renewing leases, retrying, etc. All you have to do is handle the cases where TurboFloat talks to your app and tells it something has changed (license lease failing to be renewed or new license field data). To do this you need to handle the LeaseChange event. Here we add a new event handler before we request a lease:

    'TODO: goto the version page at LimeLM and paste this GUID here
    tf = New TurboFloat("PASTE-VERSION-GUID-HERE")

    AddHandler tf.LeaseChange, AddressOf TurboFloat_LeaseChange

Then, add the "TurboFloat_LeaseChange()" function to handle notifications from the TurboFloat library:

Private Sub TurboFloat_LeaseChange(sender As Object, e As StatusArgs)

    If e.Status = TF_LeaseStatus.TF_CB_FEATURES_CHANGED Then
        'TODO: if you're using feature values in your app
        '      you might want to reload them now.

    ElseIf e.Status = TF_LeaseStatus.TF_CB_LEASE_REGAINED Then

        ' we got the lease back, close the lease expired dialog
        ' And resume the application
        If Not IsNothing(frmLeaseExp) Then
            frmLeaseExp.DialogResult = DialogResult.OK
        End If

    Else ' TF_CB_EXPIRED, TF_CB_EXPIRED_INET, and everything else

        ' Immediately disable the app and/or show a modal
        ' form that gives the user the option to Save /
        ' Save As the data (if applicable) and let the
        ' user re-try connecting to the server.

        Enabled = False

        'Note: Don't just close your app. Your users will be
        '      rightfully ticked-off if you do something like that.

        ' Instead, we're showing a modal dialog that lets the
        ' user try to get a new lease from the server. Or,
        ' if they can't, then save their data.

        frmLeaseExp = New LeaseExpired(tf) With {
                .TopMost = True,
                .StartPosition = FormStartPosition.CenterParent
        AddHandler frmLeaseExp.FormClosed, AddressOf FrmLeaseExp_FormClosed
    End If
End Sub

Private Sub FrmLeaseExp_FormClosed(sender As Object, e As FormClosedEventArgs)
    ' prevent the closing event from firing again
    RemoveHandler frmLeaseExp.FormClosed, AddressOf FrmLeaseExp_FormClosed

    If frmLeaseExp.DialogResult = DialogResult.Cancel Then
        frmLeaseExp = Nothing

        ' close the app
        Exit Sub
    End If

    frmLeaseExp = Nothing

    ' We've gotten a new lease, so re-enable the app.
    Enabled = True
End Sub

Step 4. Finishing touches

Included in the example VB.NET app are 3 forms that you might want to copy to your own application:

  1. LeaseExpired.vb: a form to show if the license lease has expired.

    Lease expired

  2. frmInternetErr.vb: a form to show if there's an internet error (that is, a server is specified, but your app couldn't connect to the server).

    Internet error

  3. ServerConfig.vb: a form to allow the end-user to enter details about where their TurboFloat Server is located.

    Config TurboFloat Server location

    This simple dialog gives your customers easy entry of the details needed to connect to their TurboFloat Server instance, whether they host it on our infrastructure using LicenseChest or they host it locally.

You've already seen example usage of the LeaseExpired form in the TurboFloat_LeaseChange() function. Here's an example usage of the ServerConfig and frmInternetErr forms. Its logic is fairly simple. First it tries to get a lease, and if that fails then it prompts the user for action:

Public Sub New()

        'TODO: goto the version page at LimeLM and paste this GUID here
        tf = New TurboFloat("PASTE-VERSION-GUID-HERE")

        AddHandler tf.LeaseChange, AddressOf TurboFloat_LeaseChange

    Catch ex As ServerException
        Dim srvConf As ServerConfig = New ServerConfig(tf)
        If srvConf.ShowDialog(Me) <> DialogResult.OK Then
            MessageBox.Show("You must specify the location of the floating license server to run YourApp.")
            Exit Sub
        End If
    Catch ex As TurboFloatException
        ' Give the user an option to try another server if they
        ' couldn't connect to the first one, or if the first one
        ' is for a different product.
        If TypeOf ex Is wyDay.TF.InternetException Or _
           TypeOf ex Is WrongServerProductException Or _
           TypeOf ex Is ServerUUIDMismatchException Or _
           TypeOf ex Is UsernameNotAllowedException Then

            Dim inetErr As frmInternetErr = New frmInternetErr(tf)
            If inetErr.ShowDialog(Me) <> DialogResult.OK Then
                ' exit the app on failure
                Exit Sub
            End If
        Else ' all other errors
            MessageBox.Show("Failed to get a lease from the floating license server: " & ex.Message)
            Exit Sub
        End If
    End Try
End Sub

Step 5. Dropping the lease when your app closes

After you've successfully requested a lease from the TurboFloat Server, the TurboFloat library integrated in your app takes care of renewing the leases automatically and silently. You'll only ever get a notification of something going wrong in the handler for the LeaseChange event that we covered in Step 3.

When your app is closing you should "drop" the lease using the DropLease() method, and cleanup the memory using the Cleanup() method:

Private Sub Form1_FormClosed(sender As Object, e As FormClosedEventArgs) Handles MyBase.FormClosed
        ' Drop the lease
        If tf.HasLease Then
        End If

        ' cleanup memory
    Catch ex As Exception
        ' we're exiting anyway, just let the lease be a zombie.
    End Try
End Sub

What this does is tell the TurboFloat Server that you're through using the lease in this instance of your app, and another instance of your app on another computer or another session can now use that "free slot".

If you can't drop the lease (because your app can't connect to the internet, or for any other reason), and you choose to exit your app anyway, then the "lease" on the TurboFloat Server will be a "zombie". The lease will expire eventually on the TurboFloat Server, and thus the free slot will open back up.

Step 6: Testing the lease change event

Testing requesting leases, dropping them, and everything else in the TurboFloat Library is intuitive: just call the function and it does the thing you want it to do. Testing the lease change event is, however, slightly less intuitive. Here's how you can test the lease change event:

  1. If your app is open and has a lease, close your app and make sure it drops the license lease from the TurboFloat Server.

  2. Stop the TurboFloat Server instance.

  3. Open the TurboFloat Server config file, and edit <lease .../> element and set it to "30". This will set the lease length to 30 seconds.

  4. Save the changes you made to the configuration file.

  5. Start your TurboFloat Server instance again.

  6. Start your app again, and make sure it successfully gets a license lease from the TurboFloat Server.

  7. Now, stop the TurboFloat Server instance, but leave your app running.

  8. Within the next 30 seconds the lease change event will be called because the TurboFloat Library was not able to renew the license lease automatically.

You should also test the "TF_CB_LEASE_DROPPED_SLEEP" and "TF_CB_LEASE_REGAINED" callback types. These callbacks are raised when your app has a lease and the device your app is running on goes to sleep and then eventually wakes up. To test these scenarios:

  1. Run a TurboFloat Server on a separate computer than the one you're running the test from (or spin up a TurboFloat Server instance on our infrastructure).

  2. Start your app and acquire a lease from that TFS instance.

  3. Put the computer which your app is running on to sleep.

  4. After the computer has gone to sleep, wake it up.

  5. Your app should handle both of those events seamlessly. Namely, prompting the user to reconnect when the computer goes to sleep, and if the lease is regained automatically, hiding that prompt from the user.