Private Sub Form_Load()
    If IsConnectedState Then
        MsgBox "连接网络"
    Else
        MsgBox "没有联网"
    End If
End Sub

Option Explicit

Private Type WSADATA
    wversion As Integer
    wHighVersion As Integer
    szDescription(0 To 256) As Byte
    szSystemStatus(0 To 128) As Byte
    iMaxSockets As Integer
    iMaxUdpDg As Integer
    lpszVendorInfo As Long
End Type

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
Private Declare Function gethostbyname Lib "WSOCK32.DLL" (ByVal szHostname As String) As Long
Private Const WS_VERSION_REQD = &H101

Public Function IsConnectedState() As Boolean
    Dim udtWSAD As WSADATA
    Call WSAStartup(WS_VERSION_REQD, udtWSAD)
    IsConnectedState = CBool(gethostbyname("www.baidu.com"))
    Call WSACleanup
End Function


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如果程序在联网处理之前能先自动判断用户是否已经联网，就可提高程序运行效率。