module1.bas

Visual Basic 6 网络编程实例教程ch01～ch02分别包含了书中各章的主要程序文件

Attribute VB_Name = "Module1"
Option Explicit

Public Const IP_SUCCESS As Long = 0
Public Const MAX_WSADescription As Long = 256
Public Const MAX_WSASYSStatus As Long = 128
Public Const WS_VERSION_REQD As Long = &H101
Public Const WS_VERSION_MAJOR As Long = WS_VERSION_REQD \ &H100 And &HFF&
Public Const WS_VERSION_MINOR As Long = WS_VERSION_REQD And &HFF&
Public Const MIN_SOCKETS_REQD As Long = 1
Public Const SOCKET_ERROR As Long = -1

Public Type HOSTENT
   hName      As Long
   hAliases   As Long
   hAddrType  As Integer
   hLen       As Integer
   hAddrList  As Long
End Type

Public Type WSADATA
   wVersion As Integer
   wHighVersion As Integer
   szDescription(0 To MAX_WSADescription) As Byte
   szSystemStatus(0 To MAX_WSASYSStatus) As Byte
   wMaxSockets As Long
   wMaxUDPDG As Long
   dwVendorInfo As Long
End Type

Private Declare Function gethostbyname Lib "WSOCK32.DLL" _
  (ByVal hostname As String) As Long
  
Private Declare Sub CopyMemory Lib "kernel32" _
   Alias "RtlMoveMemory" _
  (xDest As Any, _
   xSource As Any, _
   ByVal nbytes As Long)

Private Declare Function lstrlenA Lib "kernel32" _
  (lpString As Any) As Long

Public Declare Function WSAStartup Lib "WSOCK32.DLL" _
   (ByVal wVersionRequired As Long, _
    lpWSADATA As WSADATA) As Long
    
Public Declare Function WSACleanup Lib "WSOCK32.DLL" () As Long


Public Function SocketsInitialize() As Boolean

   Dim WSAD As WSADATA
   Dim success As Long
   SocketsInitialize = WSAStartup(WS_VERSION_REQD, WSAD) = IP_SUCCESS
End Function


Public Sub SocketsCleanup()
   If WSACleanup() <> 0 Then
       MsgBox "终止Windows Sockets时出错", vbExclamation
   End If
End Sub


Public Function GetIPFromHostName(ByVal sHostName As String) As String
  '将主机名转换为IP地址
   Dim nbytes As Long
   Dim ptrHosent As Long
   Dim ptrName As Long
   Dim ptrAddress As Long
   Dim ptrIPAddress As Long
   Dim sAddress As String
   sAddress = Space$(4)
   ptrHosent = gethostbyname(sHostName & vbNullChar)
   If ptrHosent <> 0 Then

     '分配指针的地址与偏移量
     '该地址是HOSENT的开始地址偏移了12个字节后的地址。
     '注意：这里只返回第一个地址。要想返回更多的信息，定义sAddress为一个字符串数组。
     '然后循环处理返回的4字节的ptrIPAddress成员。
      ptrAddress = ptrHosent + 12
     '获取IP地址
      CopyMemory ptrAddress, ByVal ptrAddress, 4
      CopyMemory ptrIPAddress, ByVal ptrAddress, 4
      CopyMemory ByVal sAddress, ByVal ptrIPAddress, 4
      GetIPFromHostName = IPToText(sAddress)
   End If
End Function


Private Function IPToText(ByVal IPAddress As String) As String
   IPToText = CStr(Asc(IPAddress)) & "." & _
              CStr(Asc(Mid$(IPAddress, 2, 1))) & "." & _
              CStr(Asc(Mid$(IPAddress, 3, 1))) & "." & _
              CStr(Asc(Mid$(IPAddress, 4, 1)))
End Function