Introduction:
This article describes an easy approach to building two
controls used to monitor the status of an internet connection and provide the
user with some indication of that status. Within the attached project, there
are two controls, one shows the user what the connection type is and whether or
not the machine is connected or offline, the other one is used to show some
indication of the quality of the connection in terms of whether or not the
connection is good, intermittent, or offline.
The purpose of the controls was to provide a mobile
user of a smart client application some status information regarding the
internet connection; in this instance, there were many forms within the
application and I wanted a simple control to drop on each form to provide that
status.
![Connection-State-in-vb.net.gif]()
Figure 1: Both Connection Status Controls In Use
Getting Started:
In order to get started, unzip the attachment and load
the solution into Visual Studio 2005. Examine the solution explorer and note
the files contained each of the two projects:
![solution-explorer-in-vb.net.gif]()
Figure 2: The Solution Explorer Showing the Project
Files
The "ConnectStatus" project contains the two controls
used to display internet connection status to the user; the "ConnectQualityView"
displays an indication of the quality of the status based upon how well that
connection is maintained over time. The "ConnectStateView" control shows the
type of connection and provides a graphic indicating whether or not the
connection is active or offline.
The second project, "TestAppForInetConnect" contains a
simple form used to display both controls at the same time. This second project
is not necessary as with Visual Studio 2005, the user may display the controls
in the control test container. There is no code associated with this second
project, the main form has one of each type of control loaded into it and it
serves only as a container for those controls.
The Code: ConnectStateView.
The control is quite simple; the visual elements
include only a group box and a single label. Aside from the visual elements,
there is a single timer which is used to check the status of the internet
connection repeatedly and there is a single image list which is used to hold a
couple of images used to place an icon adjacent to the label control.
If you care to open the class, you will note that there
are no imports. The control's code is pretty easy to read and is as follows:
Public
Class ConnectStateView
#Region
"Declarations"
Private ConnectionStateString
As String
Private Declare
Function InternetGetConnectedState
Lib "wininet.dll"
(ByRef _
lpSFlags
As Int32, ByVal
dwReserved As Int32)
As Boolean
Public Enum
InetConnState
modem = &H1
lan = &H2
proxy = &H4
ras = &H10
offline = &H20
configured = &H40
End Enum
#End
Region
#Region
"Control Methods"
Private Sub
ConnectStateView_Load(ByVal sender
As Object,
ByVal e As
System.EventArgs)
Handles Me.Load
Timer1.Enabled =
True
End Sub
Private Sub
Timer1_Tick(ByVal sender
As System.Object,
ByVal e As
System.EventArgs)
Handles Timer1.Tick
Dim blnState As
Boolean
blnState =
CheckInetConnection()
lblConnectStatus.Text = " Connection Type:
" &
ConnectionStateString
End Sub
Function CheckInetConnection()
As Boolean
Dim lngFlags As
Long
If InternetGetConnectedState(lngFlags, 0)
Then
' True
If lngFlags And
InetConnState.lan Then
ConnectionStateString = "LAN."
lblConnectStatus.Image = ImageList1.Images(1)
ElseIf lngFlags And
InetConnState.modem Then
ConnectionStateString = "Modem."
lblConnectStatus.Image = ImageList1.Images(1)
ElseIf lngFlags And
InetConnState.configured Then
ConnectionStateString = "Configured."
lblConnectStatus.Image = ImageList1.Images(1)
ElseIf lngFlags And
InetConnState.proxy Then
ConnectionStateString = "Proxy"
lblConnectStatus.Image = ImageList1.Images(1)
ElseIf lngFlags And
InetConnState.ras Then
ConnectionStateString = "RAS."
lblConnectStatus.Image = ImageList1.Images(1)
ElseIf lngFlags And
InetConnState.offline Then
ConnectionStateString = "Offline."
Me.lblConnectStatus.Image =
ImageList1.Images(2)
End If
Else
' False
ConnectionStateString = "Not Connected."
lblConnectStatus.Image = ImageList1.Images(3)
End If
End Function
#End
Region
End
Class
In the beginning of the code, note that there is a
region called "Declarations" defined and within that region there are three
declarations. The first declaration defines a string value that is used to keep
track of the connection type used by the client's machine.
The next declaration is the most important part of the
code, it is the code that exposes a function from the wininet.dll to the
application; that function is called "InternetGetConnectedState". This function
accepts two arguments which in this case are two 32 bit integers; these could be
longs but integers work fine here; the function returns a boolean but also could
be set up to return a long integer as well. In use, empty values of the
specified data types are passed to this function and the function then sets
their values. To use the control, these set values are evaluated in code to
determine the type and status of the current internet connection.
The last declaration is of an enumeration used to
contain representatives of each connection type exposed by the previous
function. The flags identified in the enumeration are representative of each
connection type that may be returned from making a call to the wininet.dll
function declared previously.
After the declarations region is closed, a new region
entitled "Control Methods" is defined. The first item in this section is the
control load event handler; in this section, the timer is enabled and process of
polling the internet connection of the timer's interval is initialized.
After the load event code, the handler for the timer is
defined. The handler is used to evoke the "InternetGetConnectedState" function
through a call to the "CheckInetConnect" method. This code calls the next
method in line, "CheckInetConnection" which sets the text contained in the label
based upon the value of the "ConnectionStateString" which is in turn updated by
the "CheckInetConnection" method.
The "CheckInetConnection" method calls the wininet.dll
method "InternetGetConnectedState" which in turn sets the flag and connection
type arguments used to determine the status of the internet connection. At the
beginning of the evaluation, the first check determines whether or not the
machine is connected; if the machine is connected, each pair is evaluated to
determine the type of connection and to set the label text and icon to reflect
the status returned by the method. If the connection is not active, the else
block will execute and the label text and icon will update to show that the
system is not connected (see bottom control in figure 3).
![test-application-vb.net.gif]()
Figure 3: Connection Status Controls with Failed
Internet Connection
That is all there is to the code for this first
control. The next section will discuss the content of the second control as
used to gauge the quality of an internet connection.
The Code: ConnectQualityView.
This control is used to give a rough estimate as the
quality of the internet connection as a function of the durability and
persistence of the connection over a brief time span (3 seconds). The code
contained within this class if nearly identical to the previous class; it is as
follows:
Public
Class ConnectQualityView
#Region
"Declarations"
Dim ConnectionQualityString
As String =
"Off"
Private Declare
Function InternetGetConnectedState
Lib "wininet.dll"
(ByRef _
lpSFlags
As Int32, ByVal
dwReserved As Int32)
As Boolean
Public Enum
InetConnState
modem = &H1
lan = &H2
proxy = &H4
ras = &H10
offline = &H20
configured = &H40
End Enum
#End
Region
#Region
"Control Methods"
Private Sub
ConnectQualityView_Load(ByVal sender
As Object,
ByVal e As
System.EventArgs)
Handles Me.Load
Timer1.Enabled =
True
Me.DoubleBuffered =
True
End Sub
Private Sub
Timer1_Tick(ByVal sender
As System.Object,
ByVal e As
System.EventArgs)
Handles Timer1.Tick
lblConnectStatus.Refresh()
Dim
blnState As Boolean
blnState =
CheckInetConnection()
End Sub
Function CheckInetConnection()
As Boolean
Dim lngFlags As
Long
If InternetGetConnectedState(lngFlags, 0)
Then
' True
If lngFlags And
InetConnState.lan Then
Select Case
ConnectionQualityString
Case "Good"
lblConnectStatus.ForeColor = Color.Green
lblConnectStatus.Text = "Connection Quality: Good"
ConnectionQualityString
= "Good"
Case "Intermittent"
lblConnectStatus.ForeColor = Color.Green
lblConnectStatus.Text = "Connection Quality: Good"
ConnectionQualityString
= "Good"
Case "Off"
lblConnectStatus.ForeColor = Color.DarkOrange
lblConnectStatus.Text = "Connection Quality:
Intermittent"
ConnectionQualityString = "Intermittent"
End Select
Me.Refresh()
ElseIf lngFlags And
InetConnState.modem Then
Select Case
ConnectionQualityString
Case "Good"
lblConnectStatus.ForeColor = Color.Green
lblConnectStatus.Text = "Connection Quality: Good"
ConnectionQualityString = "Good"
Case "Intermittent"
lblConnectStatus.ForeColor = Color.Green
lblConnectStatus.Text = "Connection Quality: Good"
ConnectionQualityString = "Good"
Case "Off"
lblConnectStatus.ForeColor = Color.DarkOrange
lblConnectStatus.Text =
"Connection Quality: Intermittent"
ConnectionQualityString = "Intermittent"
End Select
ElseIf lngFlags And
InetConnState.configured Then
Select Case
ConnectionQualityString
Case "Good"
lblConnectStatus.ForeColor = Color.Green
lblConnectStatus.Text = "Connection Quality: Good"
ConnectionQualityString = "Good"
Case "Intermittent"
lblConnectStatus.ForeColor = Color.Green
lblConnectStatus.Text = "Connection Quality: Good"
ConnectionQualityString = "Good"
Case
"Off"
lblConnectStatus.ForeColor = Color.DarkOrange
lblConnectStatus.Text = "Connection Quality:
Intermittent"
ConnectionQualityString = "Intermittent"
End Select
ElseIf lngFlags And
InetConnState.proxy Then
Select Case
ConnectionQualityString
Case "Good"
lblConnectStatus.ForeColor = Color.Green
lblConnectStatus.Text = "Connection Quality: Good"
ConnectionQualityString = "Good"
Case "Intermittent"
lblConnectStatus.ForeColor = Color.Green
lblConnectStatus.Text = "Connection Quality: Good"
ConnectionQualityString = "Good"
Case "Off"
lblConnectStatus.ForeColor = Color.DarkOrange
lblConnectStatus.Text = "Connection Quality:
Intermittent"
ConnectionQualityString = "Intermittent"
End Select
ElseIf lngFlags And
InetConnState.ras Then
Select Case
ConnectionQualityString
Case "Good"
lblConnectStatus.ForeColor = Color.Green
lblConnectStatus.Text = "Connection Quality: Good"
ConnectionQualityString = "Good"
Case "Intermittent"
lblConnectStatus.ForeColor = Color.Green
lblConnectStatus.Text = "Connection Quality: Good"
ConnectionQualityString = "Good"
Case "Off"
lblConnectStatus.ForeColor = Color.DarkOrange
lblConnectStatus.Text = "Connection Quality:
Intermittent"
ConnectionQualityString = "Intermittent"
End Select
ElseIf lngFlags And
InetConnState.offline Then
Select Case
ConnectionQualityString
Case "Good"
lblConnectStatus.ForeColor = Color.Green
lblConnectStatus.Text = "Connection Quality: Good"
ConnectionQualityString = "Good"
Case "Intermittent"
lblConnectStatus.ForeColor = Color.Green
lblConnectStatus.Text = "Connection Quality: Good"
ConnectionQualityString = "Good"
Case
"Off"
lblConnectStatus.ForeColor = Color.DarkOrange
lblConnectStatus.Text = "Connection Quality:
Intermittent"
ConnectionQualityString = "Intermittent"
End Select
End If
Else
' False
Select Case
ConnectionQualityString
Case "Good"
lblConnectStatus.ForeColor = Color.DarkOrange
lblConnectStatus.Text = "Connection Quality:
Intermittent"
ConnectionQualityString = "Intermittent"
Case "Intermittent"
lblConnectStatus.ForeColor = Color.Red
lblConnectStatus.Text = "Connection Quality: Off"
ConnectionQualityString = "Off"
Case "Off"
lblConnectStatus.ForeColor = Color.Red
lblConnectStatus.Text = "Connection Quality: Off"
ConnectionQualityString = "Off"
End Select
End If
End Function
#End
Region
End
Class
In reviewing this code in contrast to the previous
class described, you will see the only real difference is that the status is
used to set the text and fore color of the label control used to display the
status, and you will notice that the previous status message (gathered 1.5
seconds earlier) is evaluated to determine how to the display the status of the
connection. This operates under a simple notion of promoting the status of the
connection for remaining active over time. The control initializes with the
connection quality string value set to "Off", when the connection state is
evaluated, the initial connection state is noted and the code promotes the
status to intermittent. If the status remains active for an additional 1.5
seconds, it is promoted to "Good". The idea here is that if the connection is
dropping off and getting picked back up, the code will continually evaluate the
current status against the previous status and promote or demote the status
between the three available options of Good, Intermittent, and Off.
Naturally you may alter the amount of time between
status checks and in so doing, increase or decrease the amount of time necessary
to promote or demote the status of the connection.
That is all there is to the second control.
Summary.
Whilst this example project demonstrates a couple of
ways in which you can monitor and display status regarding a machine's internet
connection, these approaches do not represent all of the ways that you may
accomplish this task. Still and all, this approach is a simple and easy way to
display connection status information to your users.