How to use SNMP in a Visual Basic project

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.

The most important functions of the SFtp object are:

Connect - connect to the (remote) FTP server on port 22 or any alternate port;
Disconnect - to diconnect after a connect call;
GetCurrentDir - retrieve the current directory;
ChangeDir - change the current directory;
CreateDir - create a new directory;
RenameDir - rename a directory;
DeleteDir - delete a directory;
FindFile - find a specific file in the current directory;
FindFirstFile - iterate over all files in the current directory; find the first file;
FindNextFile - iterate over all files in the current directory; find the next file;
RenameFile - rename a file in the current directory;
DeleteFile - delete a file in the current directory;
GetFile - get (download) a file;
PutFile - put (upload) a file;

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':

(Click on the picture to enlarge)

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 on the picture to enlarge)

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

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

(Click on the picture to enlarge)

On top of your code, declare the following object:

Public objSnmp As AxNetwork.Snmp

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 objSnmp = CreateObject("AxNetwork.Snmp")

Appendix: Full source code

Option Explicit

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

Dim objSnmpManager As SnmpManager
Dim objSnmpObject As SnmpObject
Dim objConstants As NwConstants

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

Dim bOpen As Boolean
Dim lCurrentType As Long

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

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()
    Set objSnmpManager = CreateObject("AxNetwork.SnmpManager")
    Set objConstants = CreateObject("AxNetwork.NwConstants")
    
    cmbVersion.AddItem ("V1")
    cmbVersion.AddItem ("V2C")
    cmbVersion.ListIndex = 1
    
    objSnmpManager.Initialize
    
    SetDefaultLogFile
    
    EnableControls
    
End Sub

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

Private Sub btnClose_Click()
    objSnmpManager.Close
    
    bOpen = False
    
    EnableControls
End Sub

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

Private Sub btnGet_Click()
    
    If bOpen = True Then
        MousePointer = vbHourglass
        Dim objSnmpObject
        Set objSnmpObject = objSnmpManager.Get(txtOID.Text)
        If ShowResult = 0 Then
            txtOID = objSnmpObject.OID
            txtOIDName = objSnmpObject.OIDName
            txtValue = objSnmpObject.Value
            lCurrentType = objSnmpObject.Type
            
            If (optHex.Value = True) Then
              txtValue = StringToHex(objSnmpObject.Value)
            End If
            
            EnableRadioBoxes (lCurrentType)
            
            GetType
        End If
        Set objSnmpObject = Nothing
        MousePointer = vbDefault
    End If
End Sub

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

Private Sub btnGetNext_Click()
    If bOpen = True Then
        MousePointer = vbHourglass
        Set objSnmpObject = objSnmpManager.GetNext()
        If ShowResult = 0 Then
            txtOID = objSnmpObject.OID
            txtOIDName = objSnmpObject.OIDName
            txtValue = objSnmpObject.Value
            lCurrentType = objSnmpObject.Type
            
            If (optHex.Value = True) Then
              txtValue = StringToHex(objSnmpObject.Value)
            End If
            
            EnableRadioBoxes (lCurrentType)
            
            GetType
        End If
        MousePointer = vbDefault
    End If
    
End Sub

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

Private Sub btnOpen_Click()
    objSnmpManager.LogFile = txtLogFile.Text
    
    objSnmpManager.ProtocolVersion = cmbVersion.ListIndex + 1
    
    If (txtMibFile.Text <> "") Then
        objSnmpManager.LoadMibFile (txtMibFile.Text)
        
        If (ShowResult <> 0) Then
            Exit Sub
        End If
    End If
    
    objSnmpManager.Open txtAgent.Text, txtCommunity.Text, CInt(txtPort.Text)
    
    If (ShowResult = 0) Then
        bOpen = True
        EnableControls
    End If
End Sub

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

Private Sub btnSet_Click()
    If bOpen = True Then
        MousePointer = vbHourglass
        Set objSnmpObject = CreateObject("AxNetwork.SnmpObject")
        
        objSnmpObject.Clear
        objSnmpObject.Type = lCurrentType
        objSnmpObject.Value = txtNewValue.Text
        objSnmpObject.OID = txtOID.Text
        objSnmpObject.OIDName = txtOIDName.Text
        
        objSnmpManager.Set objSnmpObject
        MousePointer = vbDefault
        ShowResult
    End If
End Sub

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

Private Sub btnBrowse_Click()
    With dlgOpenFile
    .DefaultExt = "mib"
    .DialogTitle = "Select MIB file"
    .InitDir = "C:\"
    .Filter = "All MIB Files|*.mib"
    .FilterIndex = 1
    .ShowOpen
    End With
    
    txtMibFile.Text = dlgOpenFile.FileName
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

'///////////////////////////////////////////////////////////////////////
Public Function StringToHex(ByVal str As String) As String
  Dim X As Long, hexchar As String
  
  For X = 1 To Len(str)
    hexchar = Hex$(AscW(Mid$(str, X, 1)))
    If Len(hexchar) = 1 Then hexchar = "0" & hexchar
    StringToHex = StringToHex & hexchar & " "
  Next X
End Function

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

Function EnableRadioBoxes(intType As Integer)
 If (intType = objConstants.nwSNMP_TYPE_OCTETSTRING) Then
   optHex.Enabled = True
   optAscii.Enabled = True
 Else
   optHex.Enabled = False
   optAscii.Enabled = False
 End If
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) & "Snmp.log"
  Else
      txtLogFile.Text = "C:\Snmp.log"
  End If
End Function

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

Private Function ShowResult()
  ShowResult = objSnmpManager.LastError
  txtResult.Text = ShowResult & ": " & objSnmpManager.GetErrorDescription(ShowResult)
End Function

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

Private Sub EnableControls()
  btnOpen.Enabled = Not bOpen
  btnClose.Enabled = bOpen
  txtOID.Enabled = bOpen
  txtOIDName.Enabled = bOpen
  txtType.Enabled = bOpen
  txtValue.Enabled = bOpen
  txtNewValue.Enabled = bOpen
  btnGet.Enabled = bOpen
  btnGetNext.Enabled = bOpen
  btnSet.Enabled = bOpen
  optAscii.Enabled = bOpen
  optHex.Enabled = bOpen
End Sub

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

Private Sub GetType()
  txtType.Text = ""
  
  Select Case lCurrentType
  Case objConstants.nwSNMP_TYPE_BITS
      txtType.Text = "ASN_BITS"
  Case objConstants.nwSNMP_TYPE_COUNTER32
      txtType.Text = "ASN_COUNTER32"
  Case objConstants.nwSNMP_TYPE_COUNTER64
      txtType.Text = "ASN_COUNTER64"
  Case objConstants.nwSNMP_TYPE_TIMETICKS
      txtType.Text = "ASN_TIMETICKS"
  Case objConstants.nwSNMP_TYPE_OCTETSTRING
      txtType.Text = "ASN_OCTETSTRING"
  Case objConstants.nwSNMP_TYPE_GAUGE32
      txtType.Text = "ASN_GAUGE32"
  Case objConstants.nwSNMP_TYPE_IPADDRESS
      txtType.Text = "ASN_IPADDRESS"
  Case objConstants.nwSNMP_TYPE_OPAQUE
      txtType.Text = "ASN_OPAQUE"
  Case objConstants.nwSNMP_TYPE_UNSIGNED32
      txtType.Text = "ASN_UNSIGNED32"
  Case objConstants.nwSNMP_TYPE_OBJECTIDENTIFIER
      txtType.Text = "ASN_OBJECTIDENTIFIER"
  Case objConstants.nwSNMP_TYPE_NULL
      txtType.Text = "ASN_NULL"
  Case objConstants.nwSNMP_TYPE_INTEGER
      txtType.Text = "ASN_INTEGER"
  Case objConstants.nwSNMP_TYPE_INTEGER32
      txtType.Text = "ASN_INTEGER32"
  Case objConstants.nwSNMP_TYPE_SEQUENCE
      txtType.Text = "ASN_SEQUENCE"
  End Select
End Sub

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

Private Sub optAscii_Click()
  optHex.Value = False
  
  If (Trim(txtValue.Text) <> "") Then
    btnGet_Click
  End If
  
End Sub

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

Private Sub optHex_Click()
  optAscii.Value = False

  If (Trim(txtValue.Text) <> "") Then
    btnGet_Click
  End If
End Sub

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.