Microsoft Internet Transfer Control Visual Basic Example - Axis ...

Microsoft Internet Transfer Control Visual Basic Example
These examples will give you a first look at how the Internet Transfer Control can be used in the Microsoft Visual
Basic environment. Please see the Inet documentation, for more details about supported methods and properties.
In these examples, you will learn how to:
�� Add an ActiveX control to a VB project.
�� Remove an ActiveX control from a VB project.
�� Retrieve an image from an AXIS camera/video server save it to a file.
�� Log on to protected servers.
�� Set and get parameters in an AXIS camera/video server.
What is the Internet Transfer Control?
The Internet Transfer control provides implementation of two of the most widely used protocols on the Internet,
HyperText Transfer Protocol (HTTP) and File Transfer Protocol (FTP).
Using the HTTP protocol, you can connect to World Wide Web servers to retrieve HTML documents. With the FTP
protocol, you can log on to FTP servers to download and upload files. The UserName and Password properties
allow you to log on to private servers that require authentication. Otherwise, you can connect to public FTP servers
and download files. Common FTP commands, such as CD and GET, are supported through the Execute method.
Adding Controls to a Project
The set of controls available in the toolbox can be customized for each project. Any given control must be in the
toolbox before you can add it to a form in the project.
Adding ActiveX Controls to a Project
You can add ActiveX controls and insertable objects to your project by adding them to the toolbox.
To add a control to a project's toolbox:
1. From the Project menu, choose Components.
The Components dialog box is displayed. The items listed in this dialog box include all registered ActiveX
controls, insertable objects, and ActiveX designers.
2. To add the Microsoft Internet Transfer Control to the toolbox, select the checkbox to the left of the
control name.
3. Choose OK to close the Components dialog box. All of the ActiveX controls that you selected will now
appear in the toolbox.
To add ActiveX controls to the Components dialog box, select the Browse button, and search other directories for
files with an .ocx file name extension
Axis Communications AB does not provide support for application development of any kind. The information here
is provided "as is", and there is no guarantee that any of the examples shown will work in your particular
application.
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Removing Controls from a Project
To remove a control from a project:
1. From the Project menu, choose Components.
The Components dialog box is displayed.
2. Clear the check box next to each control you want to remove.
The control icons will be removed from the toolbox.
Note: You cannot remove a control from the toolbox if an instance of that control is used on any form in the project.
Using the Internet Transfer Control
The Internet Transfer control implements two widely used Internet protocols: the HyperText Transfer Protocol
(HTTP) and the File Transfer Protocol (FTP). Using the Internet Transfer control, you can connect to any site that
uses one of these protocols, and retrieve files using either the OpenURL or Execute method.
Possible Uses
�� Add an FTP browser to any application.
�� Create an application that automatically downloads files from a public FTP site.
�� Parse a World Wide Web site for graphics references and download the graphics only.
�� Present a custom display of dynamic data retrieved from a Web page.
•=
Basic Operation
The functionality of the Internet Transfer control depends on the protocol you wish to use. Because the two
supported protocols work differently, the operations you can perform depend on which protocol you are using. For
example, the GetHeader method only works with HTTP (HTML documents).
However, there are a few procedures that are common to both protocols. Basically, in order to use either protocol,
you must:
1. Set the AccessType property to a valid proxy server
2. Invoke the OpenURL method with a valid URL
3. Invoke the Execute method to retrieve data from the buffer
4. Use the GetChunk method to retrieve data from the buffer
Saving an Image to a File Using the OpenURL Method
If you wish to save the data retrieved through the OpenURL method to a file, use the Open, Put, and Close
statements, as shown in the code below. This example streams a Jpeg image into a Byte array before saving the data
to disk. The following code uses a Command Button control, cmdWriteFile. Set the caption of
cmdWriteFile to WriteFile.
The IP address in the URL should be the correct IP address to an AXIS camera/video server. See the HTTP API for
the AXIS camera/video servers for more information. A trick to figure out the correct Motion JPEG URL for the
specific Axis Camera/Video product is to look in the html code of the internal web pages. To verify that you have
the correct URL, use Netscape Navigator and type the complete Motion JPEG URL into the location window. If the
URL is correct you will, for a period of time, see live updated images in your browser.
Axis Communications AB does not provide support for application development of any kind. The information here
is provided "as is", and there is no guarantee that any of the examples shown will work in your particular
application.
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Private Sub cmdWriteFile_Click()
Dim b() As Byte
End Sub
' Set the internet transfer control protocol and URL.
Inet1.Protocol = icHTTP
Inet1.URL = "http://10.13.9.46/axis-cgi/jpg/image.cgi"
' Retrieve the HTML data into a byte array.
b() = Inet1.OpenURL(Inet1.URL, icByteArray)
' Create a local file from the retrieved data.
Open "C:\Image.jpg" For Binary Access Write As #1
Put #1, , b()
Close #1
MsgBox "Done"
Logging on to Protected Servers
Servers come in two flavors: public and private. Public servers are, as suggested by the name, open to anyone.
Private servers on the other hand, won't let you log on unless you are a bona fide user of the server.
If you are logging on to a private server, simply set the UserName and Password properties as shown in the example
below:
Inet1.UserName = "UserName"
Inet1.Password = "Password"
Set and Get Parameters in an AXIS Camera/Video Server
The Internet Transfer control can be used to set and get parameters in an AXIS camera/video server. See the
HTTP API for the AXIS camera/video servers for more information on how the URLs to set and get parameters
should look like.
The following example uses a TextBox control, Text1, and three Command Button controls,
cmdGetBrightness, cmdSetLowBrightness and cmdSetHighBrightness. Set the captions of the
buttons to Get Brightness, Set Low Brightness and Set High Brightness.
Private Sub cmdGetBrightness_Click()
Text1.Text = Inet1.OpenURL("http://10.13.9.48/axiscgi/admin/getparam.cgi?Image.Brightness")
End Sub
Axis Communications AB does not provide support for application development of any kind. The information here
is provided "as is", and there is no guarantee that any of the examples shown will work in your particular
application.
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Private Sub cmdSetLowBrightness_Click()
Text1.Text = Inet1.OpenURL("http://10.13.9.48/axiscgi/admin/setparam.cgi?Image.Brightness=0")
End Sub
Private Sub cmdSetHighBrightness_Click()
Text1.Text = Inet1.OpenURL("http://10.13.9.48/axiscgi/admin/setparam.cgi?Image.Brightness=15")
End Sub
If you, at the same time as you press the different buttons, look at a browser window showing live images from the
server, you will see the brightness of the image change.
Axis Communications AB does not provide support for application development of any kind. The information here
is provided "as is", and there is no guarantee that any of the examples shown will work in your particular
application.
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