LAN Messenger

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Introduction

This is a tool which is created using the Active Directory objects in VB.NET. Using this tool, we can communicate with the computers across the network.

Once the form is loaded, it will bring out all the computer names in a TreeView control. If you click on any computer name from the tree view, it will display the selected item in the right top textbox; it will show the computer name and also the IP address details below.

We have to type the message that we want to send, in the Message to Send box, and if you press the Send button, it will send the message to the selected computer.

In the same way, if we want to send messages to all the computers, if we press the Send to All button, it will send the message to all the computers; we also have a provision to ‘ping’ the selected node.

For sending messages to another computer, we have a ‘Net Send’ command; it is a DOS command. To run any executable program, we have a ‘Shell’ command.

Shell("net send " & txtcomputer.Text & " " & txtmessage.Text)

The above line is part of the code which will send a message to a specified computer.

To Ping the another node, the following is the command:

Shell("PING " & TextBox1.Text)

In the ‘TextBox1’, we will have the IP address of the selected computer.

To get the IP Address of the computer using the tool, we have a generic function called “GetIPAddress”.

Function GetIPAddress(ByVal CompName As String) As String
Dim oAddr As System.Net.IPAddress
Dim sAddr As String
  Try
    With System.Net.Dns.GetHostByName(CompName)
oAddr = New System.Net.IPAddress(.AddressList(0).Address)
sAddr = oAddr.ToString
          End With
          GetIPAddress = sAddr
  Catch Excep As Exception
    MsgBox(Excep.Message, MsgBoxStyle.OKOnly, "Lan Messenger")
  Finally
  
  End Try
End Function

System.Net.Dns.GetHostByName

Gets the DNS information for a specified DNS host name. Only we have to pass the ‘hostname’. Returns the host information for the address specified in hostName.

System.Net.IPAddress

Provides an Internet Protocol (IP) address. The following is the code to list the computers in the network:

Dim childEntry As DirectoryEntry
Dim ParentEntry As New DirectoryEntry()
Try
  ParentEntry.Path = "WinNT:"
  For Each childEntry In ParentEntry.Children
      Dim newNode As New TreeNode(childEntry.Name)
      Select Case childEntry.SchemaClassName
             Case "Domain"
             Dim ParentDomain As New TreeNode(childEntry.Name)
             TreeView1.Nodes.AddRange(New TreeNode() {ParentDomain})
             Dim SubChildEntry As DirectoryEntry
             Dim SubParentEntry As New DirectoryEntry()
             SubParentEntry.Path = "WinNT://" & childEntry.Name
             For Each SubChildEntry In SubParentEntry.Children
                 Dim newNode1 As New TreeNode(SubChildEntry.Name)
                 Select Case SubChildEntry.SchemaClassName
                        Case "Computer"
                              ParentDomain.Nodes.Add(newNode1)
                 End Select
              Next
      End Select
  Next
  Catch Excep As Exception
        MsgBox("Error While Reading Directories")
  Finally
       ParentEntry = Nothing
End Try

System.DirectoryServices

The .NET Framework System.DirectoryServices namespace is a robust and flexible API for querying and manipulating objects in Microsoft's Active Directory.

Active Directory is Microsoft's network operating system (NOS) directory, built on top of Windows 2000 and Windows Server 2003. It enables administrators to manage enterprise-wide information efficiently from a central repository that can be globally distributed.

The two main classes within System.DirectoryServices are DirectoryEntry and DirectorySearcher. The DirectoryEntry class represents an object in the directory, and can be used to create new objects and manage existing ones.

License

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