Windows API Guide: MAKELCID Macro


Declare Function ntohl Lib "wsock32.dll" (ByVal hostlong As Long) As Long

Platforms

  • Windows 95: Supported.
  • Windows 98: Supported.
  • Windows NT: Requires Windows NT 3.1 or later.
  • Windows 2000: Supported.
  • Windows CE: Requires Windows CE 1.0 or later.

Description & Usage

ntohl converts a 32-bit network address from network byte order to host byte order. Since the TCP/IP protocol uses big-endian byte order for network addresses, nothl ensures that the proper byte order is being used when manipulating IP addresses locally, regardless of whether the platform uses little-endian or big-endian ordering.

Return Value

The function returns the address converted to host byte order.

Visual Basic-Specific Issues

None.

Parameters

hostlong
A 32-bit network address in network order to be converted to host byte order.

Example

When the form window opens, create an IP address control in the upper-left corner and initialize it to the IP address of the computer. No special effort is needed to run this example, since the IP Address control is created programmatically when the form loads.

' This code is licensed according to the terms and conditions listed here. ' Declarations and such needed for the example: ' (Copy them to the (declarations) section of a module.) Public Type WSADATA wVersion As Integer wHighVersion As Integer szDescription As String * 257 szSystemStatus As String * 129 iMaxSockets As Long iMaxUdpDg As Long lpVendorInfo As Long End Type  Public Declare Function WSAStartup Lib "wsock32.dll" (ByVal wVersionRequested As Integer, lpWSAData _ As WSADATA) As Long Public Declare Function WSACleanup Lib "wsock32.dll" () As Long Public Type HOSTENT h_name As Long h_aliases As Long h_addrtype As Integer h_length As Integer h_addr_list As Long End Type Public Const AF_INET = 2 Public Declare Function gethostname Lib "wsock32.dll" (ByVal name As String, ByVal namelen As Long) As Long Public Declare Function gethostbyname Lib "wsock32.dll" (ByVal name As String) As Long Public Declare Function ntohl Lib "wsock32.dll" (ByVal hostlong As Long) As Long Public Declare Sub CopyMemory Lib "kernel32.dll" Alias "RtlMoveMemory" (Destination As Any, Source _ As Any, ByVal length As Long) Public Declare Function lstrlen Lib "kernel32.dll" Alias "lstrlenA" (ByVal lpString As Any) As Long Public Declare Function lstrcpy Lib "kernel32.dll" Alias "lstrcpyA" (ByVal lpString1 As Any, ByVal _ lpString2 As Any) As Long Public Type INITCOMMONCONTROLSEX_TYPE dwSize As Long dwICC As Long End Type Public Declare Function InitCommonControlsEx Lib "comctl32.dll" (lpInitCtrls As _ INITCOMMONCONTROLSEX_TYPE) As Long Public Const ICC_INTERNET_CLASSES = &H800 Public Declare Function CreateWindowEx Lib "user32.dll" Alias "CreateWindowExA" (ByVal dwExStyle As Long, _ ByVal lpClassName As String, ByVal lpWindowName As String, ByVal dwStyle As Long, ByVal x _ As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hWndParent As Long, _ ByVal hMenu As Long, ByVal hInstance As Long, lpParam As Any) As Long Public Const WC_IPADDRESS = "SysIPAddress32" Public Const WS_CHILD = &H40000000 Public Const WS_VISIBLE = &H10000000 Public Declare Function DestroyWindow Lib "user32.dll" (ByVal hWnd As Long) As Long Public Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" (ByVal hWnd As Long, ByVal Msg _ As Long, wParam As Any, lParam As Any) As Long Public Const IPM_SETADDRESS = &H465 ' Define a relevant API macro. Public Function MAKEWORD(ByVal bLow As Byte, ByVal bHigh As Byte) As Integer MAKEWORD = Val("&H" & Right("00" & Hex(bHigh), 2) & Right("00" & Hex(bLow), 2)) End Function ' *** Place the following code inside the form window. *** Private hIPControl As Long  ' handle to the IP Address control ' When the form is initialized, create an IP Address control in the ' upper-left corner of the form. Private Sub Form_Initialize() Dim comctls As INITCOMMONCONTROLSEX_TYPE  ' identifies the control to register Dim sockinfo As WSADATA  ' information about Winsock Dim hostinfo As HOSTENT  ' information about an Internet host Dim pHostinfo As Long    ' pointer to a HOSTENT structure Dim localhostName As String  ' the computer's domain name Dim pIPAddress As Long   ' pointer to an IP address dword Dim ipAddress_n As Long    ' the IP address in network byte order Dim ipAddress_h As Long  ' the IP address in host byte order Dim retval As Long                        ' generic return value ' Register the IP Address control window class. With comctls .dwSize = Len(comctls) .dwICC = ICC_INTERNET_CLASSES End With retval = InitCommonControlsEx(comctls) ' Create the IP Address control in the corner of the window. hIPControl = CreateWindowEx(0, WC_IPADDRESS, "", WS_CHILD Or WS_VISIBLE, 0, 0, 125, 20, _ Me.hWnd, 0, App.hInstance, ByVal CLng(0)) ' Open a new Winsock session (version 2.2). retval = WSAStartup(MAKEWORD(2, 2), sockinfo) If retval <> 0 Then Debug.Print "ERROR: Attempt to open Winsock failed: error"; retval Exit Sub End If ' Get the domain name of the computer, or, failing that, a string ' that gethostbyname can handle to give an IP address. localhostName = Space(256) retval = gethostname(localhostName, 256) localhostName = Left(localhostName, InStr(localhostName, vbNullChar) - 1) ' Get information about this computer on the network. ' Get information about the domain specified in txtDomain. pHostinfo = gethostbyname(localhostName) If pHostinfo = 0 Then Debug.Print "Unable to resolve domain name." Else ' Copy the data into a HOSTENT structure. CopyMemory hostinfo, ByVal pHostinfo, Len(hostinfo) If hostinfo.h_addrtype <> AF_INET Then Debug.Print "A non-IP address was returned." Else ' Copy the pointer to the first (and probably only) IP address in the structure. CopyMemory pIPAddress, ByVal hostinfo.h_addr_list, 4 ' Copy the actual IP address. CopyMemory ipAddress_n, ByVal pIPAddress, 4 ' Convert it to host byte order. ipAddress_h = ntohl(ipAddress_n) ' Set the IP Address control to hold this address. retval = SendMessage(hIPControl, IPM_SETADDRESS, _ ByVal CLng(0), ByVal ipAddress_h) End If End If End Sub ' Destroy the IP Address control when the form closes. Private Sub Form_Unload(Cancel As Integer) Dim retval As Long  ' return value retval = DestroyWindow(hIPControl) End Sub

See Also

htonl

Category

Winsock

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Last Modified: October 29, 2000
This page is copyright © 2000 Paul Kuliniewicz. Copyright Information Revised October 29, 2000
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Windows API Guide
Windows API Guide - Reference - Volume 1: Version 3.0 For the MS-DOS and PC-DOS Operating Systems
ISBN: B001V0KQIY
EAN: N/A
Year: 1998
Pages: 610

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