SAMPLE: Winsock.exe Getting HostAddress Using Windows Sockets

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Article ID: 154512 - View products that this article applies to.
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This article demonstrates how to get the HostAddress of a machine using Windows Sockets. The TCP/IP network protocol is shipped with all Windows operating systems and is becoming increasingly more important with its Internet compatibility. There is an API set for Windows Sockets that can work with TCP/IP and help to return information such as the HostName or the IP Address of a machine. This is obviously reliant on the presence of the relevant DNS or WINS servers and the TCP/IP protocol being installed. Below is a sample showing how to extract the machine HostAddress.

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NOTE: This code requires at least version 1.1 of Windows Sockets.
  1. Start a new project in Visual Basic. Form1 is created by default.
  2. Place a CommandButton on the form.
  3. Add the following code to the Form1 code window:
          Option Explicit
          Private Const WSADescription_Len = 256
          Private Const WSASYS_Status_Len = 128
          Private Const SOCKET_ERROR As Long = -1
          Private Type WSADATA
             wversion As Integer
             wHighVersion As Integer
             szDescription(0 To WSADescription_Len) As Byte
             szSystemStatus(0 To WSASYS_Status_Len) As Byte
             iMaxSockets As Integer
             iMaxUdpDg As Integer
             lpszVendorInfo As Long
          End Type
             Private Declare Function gethostname Lib "WSOCK32.DLL" (ByVal hostname$, _
       ByVal HostLen As Integer) As Long
          Private Declare Function WSAGetLastError Lib "WSOCK32.DLL" _
             () As Long
          Private Declare Function WSAStartup Lib "WSOCK32.DLL" (ByVal _
             wVersionRequired as Integer, lpWSAData As WSADATA) As Long
          Private Declare Function WSACleanup Lib "WSOCK32.DLL" () As Long
          Sub Form_Load()
            Call SocketsInitialize
          End Sub
          Private Sub Command1_click()
            Dim hostname$, HostLen&
            HostLen& = 256
            hostname$ = Space$(HostLen&)
            If gethostname(hostname$, HostLen&) = SOCKET_ERROR Then
                MsgBox "Windows Sockets error" & Str(WSAGetLastError())
                hostname$ = Trim$(hostname$)
                hostname$ = Left$(hostname$, Len(hostname$) - 1)
                MsgBox "Host name  = " & hostname$
            End If
          End Sub
          Sub SocketsInitialize()
            Const WS_VERSION_REQD As Integer = &H101
            Const WS_VERSION_MAJOR = WS_VERSION_REQD \ &H100 And &HFF&
            Const MIN_SOCKETS_REQD = 1
            Dim WSAD As WSADATA
            Dim iReturn As Integer
            Dim sLowByte As String, sHighByte As String, sMsg As String
            iReturn = WSAStartup(WS_VERSION_REQD, WSAD)
            If iReturn <> 0 Then
                MsgBox "Winsock.dll is not responding."
            End If
            If lobyte(WSAD.wversion) < WS_VERSION_MAJOR Or (lobyte _
              (WSAD.wversion) = WS_VERSION_MAJOR And hibyte(WSAD.wversion) _
              < WS_VERSION_MINOR) Then
              sHighByte = Trim$(Str$(hibyte(WSAD.wversion)))
              sLowByte = Trim$(Str$(lobyte(WSAD.wversion)))
              sMsg = "Windows Sockets version " & sLowByte & "." & sHighByte
              sMsg = sMsg & " is not supported by winsock.dll "
              MsgBox sMsg:
         End If
         If WSAD.iMaxSockets < MIN_SOCKETS_REQD Then
           sMsg = "This application requires a minimum of "
           sMsg = sMsg & Trim$(Str$(MIN_SOCKETS_REQD)) & _
           " supported sockets."
           MsgBox sMsg
         End If
          End Sub
          Function hibyte(ByVal wParam As Integer)
             hibyte = wParam \ &H100 And &HFF&
          End Function
          Function lobyte(ByVal wParam As Integer)
             lobyte = wParam And &HFF&
          End Function
          Sub SocketsCleanup()
            Dim lReturn As Long
            lReturn = WSACleanup()
            If lReturn <> 0 Then
              MsgBox "Socket error " & Trim$(Str$(lReturn)) & _
       " occurred in Cleanup"
            End If
          End Sub
  4. Press the F5 key to run the project. The Hostname should be printed on the form.


Article ID: 154512 - Last Review: August 5, 2004 - Revision: 3.1
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