Visual Basic UDP Sample Source Code

Network Component provides an easy-to-use development interface to a variety of IP protocols. By using Network Component, you can very easily create or enhance applications with network features.

Network Component features the following: DNS, FTP, HTTP, HTTPs, ICMP Ping, IP-to-Country, MSN, NTP, RSH, SCP, SFTP, SNMP v1/v2c (Get, GetNext, Set), SNMP Traps, SNMP MIB, SSH, TCP, Telnet, TFTP, UDP, Telnet, Wake-On-LAN and more.

Network Component can be well integrated into any development platform that supports ActiveX objects.

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Step 1: Download and install the Network Component

Download Network Component from the ActiveXperts Download Site and start the installation. The installation guides you through the installation process.

Step 2: Create a new Visual Basic project

Launch 'Microsoft Visual Basic' from the Start menu, and choose 'New' from the 'File Menu'. The 'New Project' dialog appears.
Select 'Standard Exe' and click 'OK':

Step 3: Refer to the Network Component Library and create the objects

A new Project is created, with a blank form.

First, you must add a reference to Network Component in the project to be able to use the object. To do so, choose 'References...' from the 'Project' menu. In the 'References' dialog that pops up, enable the 'Network Component 3.1 Type Library' reference as shown in the following picture:

Click 'OK' to close the 'References...' dialog.

Then, select the Project form and choose 'View Code' from the context menu:

On top of your code, declare the following object:

Public objUdp As AxNetwork.Udp

Step 4: Create the object

From the Code window, select 'Form'. The Private Sub 'Form_Load()' will be displayed now. In the 'Form Load' function, create the object in the following way:

Set objUdp = CreateObject("AxNetwork.Udp")

Appendix: Full source code

Option Explicit
Public objSocketClient As AxNetwork.Udp
Public objSocketServer As AxNetwork.Udp

Public objConstants As AxNetwork.NwConstants

Public bServerListning As Boolean
Public bClientConnected As Boolean

Private Declare Function GetTempPath Lib "kernel32" Alias "GetTempPathA" (ByVal nBufferLength As Long, ByVal lpBuffer As String) As Long
Private Const MAX_PATH = 260

'///////////////////////////////////////////////////////////////////////

Private Sub Form_Load()
  bServerListning = False
  Set objSocketClient = CreateObject("AxNetwork.Udp")
  Set objSocketServer = CreateObject("AxNetwork.Udp")
  
  Set objConstants = CreateObject("AxNetwork.NwConstants")
  
  SetDefaultLogFile
  UpdateControls
End Sub

Private Sub UpdateControls()
  btnListen.Enabled = Not bServerListning
  btnServerClose.Enabled = bServerListning
  txtReceived.Enabled = bServerListning
  txtServerPort.Enabled = Not bServerListning
  cbIp6.Enabled = Not bServerListning
  
  txtHost.Enabled = Not bClientConnected
  txtClientPort.Enabled = Not bClientConnected
  btnOpen.Enabled = Not bClientConnected
  
  txtCommand.Enabled = bClientConnected
  btnSend.Enabled = bClientConnected
  btnClientClose.Enabled = bClientConnected
End Sub

'///////////////////////////////////////////////////////////////////////

Private Sub btnClientClose_Click()
  objSocketClient.Close
  
  If (GetClientResult() = 0) Then
    bClientConnected = False
    UpdateControls
  End If
End Sub

'///////////////////////////////////////////////////////////////////////

Private Sub btnListen_Click()
  objSocketServer.IOTimeout = 100
  objSocketServer.LogFile = txtLogFile.Text
  objSocketServer.Open "localhost", CInt(txtServerPort.Text), True, cbIp6
  
  If (GetServerResult() = 0) Then
      bServerListning = True
      UpdateControls
  End If
End Sub

'///////////////////////////////////////////////////////////////////////

Private Sub btnOpen_Click()
  objSocketClient.IOTimeout = 100
  objSocketClient.LogFile = txtLogFile.Text
  objSocketClient.Open txtHost.Text, CInt(txtClientPort.Text), False
  
  If (GetClientResult() = 0) Then
      bClientConnected = True
      UpdateControls
  End If
End Sub

'///////////////////////////////////////////////////////////////////////

Private Sub btnSend_Click()
  objSocketClient.SendString (txtCommand.Text)
End Sub

'///////////////////////////////////////////////////////////////////////

Private Sub btnServerClose_Click()
  objSocketServer.Close
  If (GetServerResult() = 0) Then
      bServerListning = False
      UpdateControls
  End If
End Sub

'///////////////////////////////////////////////////////////////////////

Private Sub Timer1_Timer()
  Dim strReceivedLine As String
  Dim strReceivedData As String
  
  strReceivedData = objSocketServer.ReceiveString
  
  If (Len(strReceivedData) <> 0) Then
      strReceivedLine = "[" + objSocketServer.RemoteAddress + "] " + strReceivedData
      txtReceived.Text = txtReceived.Text + strReceivedLine + vbCrLf
  End If
End Sub
'///////////////////////////////////////////////////////////////////////

Private Sub btnView_Click()
  If FileExists(txtLogFile.Text) = True Then
      Shell "notepad " + txtLogFile.Text, vbNormalFocus
  End If
End Sub

'///////////////////////////////////////////////////////////////////////

Public Function FileExists(sFileName As String) As Boolean
  FileExists = CBool(Len(Dir$(sFileName))) And CBool(Len(sFileName))
End Function

'///////////////////////////////////////////////////////////////////////

Private Function SetDefaultLogFile()

Dim Buffer As String
  Buffer = Space(MAX_PATH)
  
  If GetTempPath(MAX_PATH, Buffer) <> 0 Then
      txtLogFile.Text = Left$(Buffer, InStr(Buffer, vbNullChar) - 1) & "Udp.log"
  Else
      txtLogFile.Text = "C:\Udp.log"
  End If
End Function

Private Sub Form_Unload(Cancel As Integer)
  objSocketClient.Close
  objSocketServer.Close
End Sub

'///////////////////////////////////////////////////////////////////////

Private Function GetClientResult() As Long
  Dim lResult As Long

  lResult = objSocketClient.LastError
  txtClientResult.Text = lResult & ": " & objSocketClient.GetErrorDescription(lResult)
 
  GetClientResult = lResult
End Function

'///////////////////////////////////////////////////////////////////////

Private Function GetServerResult() As Long
  Dim lResult As Long

  lResult = objSocketServer.LastError
  txtServerResult.Text = lResult & ": " & objSocketServer.GetErrorDescription(lResult)
 
  GetServerResult = lResult
End Function

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You can download the complete samples here. There are many other working Network Component scripts on our site and shipped with the product.

NOTE: Demo Projects are created with Microsoft Visual Studio 2008

The Network Component project ships with a set of Microsoft Visual Studio .NET samples, including samples for Microsoft Visual C# .NET. The projects are created with Microsoft Visual Studio 2008.

Users with a later version of Microsoft Visual Studio can open such a project. The Visual Studio Conversion Wizard will guide you through the process of converting the project to the version used.