请教：如何判断两台电脑可以正常连接？

一般查看两台电脑间是否可以正常连接，用ping + 要连接电脑的IP地址或电脑名。

但我不知道怎样用语句来表达，希望各位能多多指教。

最好能达到下面这样的效果：

如果可以连接，就提示：msgbox"可以连线"

如果不能连接，就提示：msgbox"对方已关机或IP不存在！"

Option Explicit
Private Const INADDR_NONE As Long = &HFFFFFFFF
Private Const PING_TIMEOUT As Long = 500
Private Type ICMP_ECHO_REPLY
Address As Long
status As Long
RoundTripTime As Long
DataSize As Long
DataPointer As Long
Data As String * 250
End Type
Private Declare Function inet_addr Lib "WSOCK32.DLL" (ByVal s As String) As Long
Private Declare Function IcmpCreateFile Lib "icmp.dll" () As Long
Private Declare Function IcmpSendEcho Lib "icmp.dll" (ByVal IcmpHandle As Long, _
ByVal DestinationAddress As Long, ByVal RequestData As String, ByVal RequestSize As Long, _
ByVal RequestOptions As Long, ReplyBuffer As ICMP_ECHO_REPLY, ByVal ReplySize As Long, _
ByVal Timeout As Long) As Long
Private Declare Function IcmpCloseHandle Lib "icmp.dll" (ByVal IcmpHandle As Long) As Long

Public Function ping(ip As String) As Boolean
Dim ECHO As ICMP_ECHO_REPLY
Dim mystr As String
Dim hPort As Long
mystr = inet_addr(ip)
If mystr <> INADDR_NONE Then
hPort = IcmpCreateFile()
If hPort Then
Call IcmpSendEcho(hPort, mystr, 0, 0, 0, ECHO, Len(ECHO), PING_TIMEOUT) '发送回响请求报文，返回回响应答报文
Call IcmpCloseHandle(hPort)
End If

If ECHO.status = 0 Then ping = True Else ping = False

End If
End Function

Private Sub Command1_Click()
If ping(Text1.Text) Then MsgBox "可以连线" Else MsgBox "对方已关机或IP不存在！"
End Sub

Private Const WS_VERSION_REQD = &H101
Private Const WS_VERSION_MAJOR = WS_VERSION_REQD \ &H100 And &HFF&
Private Const WS_VERSION_MINOR = WS_VERSION_REQD And &HFF&
Private Const MIN_SOCKETS_REQD = 1
Private Const SOCKET_ERROR = -1
Private Const WSADescription_Len = 256
Private Const WSASYS_Status_Len = 128

Private Type HOSTENT
hname As Long
hAliases As Long
hAddrType As Integer
hLength As Integer
hAddrList As Long
End Type

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 gethostbyaddr Lib "WSOCK32.DLL" (addr As Any, ByVal _
byteslen As Integer, addrtype As Integer) As Long
Private Declare Function WSAGetLastError Lib "WSOCK32.DLL" () As Long
Private Declare Function WSAStartup Lib "WSOCK32.DLL" (ByVal _
wVersionRequired&, lpWSAData As WSADATA) As Long
Private Declare Function WSACleanup Lib "WSOCK32.DLL" () As Long
Private Declare Function gethostbyname Lib "WSOCK32.DLL" (ByVal _
hostname$) As Long
Private Declare Sub RtlMoveMemory Lib "KERNEL32" (hpvDest As Any, _
ByVal hpvSource&, ByVal cbCopy&)

Function hibyte(ByVal wParam As Integer) ’获得整数的高位
hibyte = wParam \ &H100 And &HFF&
End Function

Function lobyte(ByVal wParam As Integer) ’获得整数的低位
lobyte = wParam And &HFF&
End Function

Function SocketsInitialize()
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 没有反应."
End
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版本 " & sLowByte & "." & sHighByte
sMsg = sMsg & " 不被winsock.dll支持 "
MsgBox sMsg
End
End If

If WSAD.iMaxSockets < MIN_SOCKETS_REQD Then
sMsg = "这个系统需要的最少Sockets数为 "
sMsg = sMsg & Trim$(str$(MIN_SOCKETS_REQD))
MsgBox sMsg
End
End If

End Function

Sub SocketsCleanup()
Dim lReturn As Long

lReturn = WSACleanup()

If lReturn <> 0 Then
MsgBox "Socket错误 " & Trim$(str$(lReturn)) & " occurred in Cleanup "
End
End If
End Sub

Sub Form_Load()
’初始化Socket
SocketsInitialize
End Sub

Private Sub Form_Unload(Cancel As Integer)
’清除Socket
SocketsCleanup
End Sub
Private Function getip(name As String) As String
Dim hostent_addr As Long
Dim host As HOSTENT
Dim hostip_addr As Long
Dim temp_ip_address() As Byte
Dim i As Integer
Dim ip_address As String

hostent_addr = gethostbyname(name)

If hostent_addr = 0 Then
getip = "" ’主机名不能被解释
Exit Function
End If

RtlMoveMemory host, hostent_addr, LenB(host)
RtlMoveMemory hostip_addr, host.hAddrList, 4

ReDim temp_ip_address(1 To host.hLength)
RtlMoveMemory temp_ip_address(1), hostip_addr, host.hLength

For i = 1 To host.hLength
ip_address = ip_address & temp_ip_address(i) & "."
Next
ip_address = Mid$(ip_address, 1, Len(ip_address) - 1)

getip = ip_address

End Function

Private Sub Command1_click()
Dim str As String
str = getip(Text1.Text)
If str = "" Then
Text2.Text = "主机名不能被解释"
Else
Text2.Text = str
End If
End Sub
Private Function getname(addrstr As String) As String
Dim hostent_addr As Long
Dim host As HOSTENT
Dim addr(0 To 50) As Byte
Dim addrs As String
Dim hname(1 To 50) As Byte
Dim str As String
Dim i As Integer, j As Integer
Dim temp_int As Integer
Dim byt As Byte
str = Trim$(addrstr)
i = 0
j = 0
Do
temp_int = 0
i = i + 1
Do While Mid$(str, i, 1) >= "0" And Mid$(str, i, 1) <= "9" And i <= Len(str)
temp_int = temp_int * 10 + Mid$(str, i, 1)
i = i + 1
Loop
If temp_int <= 255 Then
addr(j) = temp_int
j = j + 1
End If

Loop Until Mid$(str, i, 1) <> "." Or i > Len(str) Or temp_int > 255
If temp_int > 255 Then
getname = "地址非法"
Exit Function
End If
hostent_addr = gethostbyaddr(addr(0), j, 2)
If hostent_addr = 0 Then
getname = "此地址无法解析"
Exit Function
End If
RtlMoveMemory host, hostent_addr, LenB(host)
RtlMoveMemory hname(1), host.hname, 50
j = 51
For i = 1 To 50
If hname(i) = 0 Then
j = i
End If
If i >= j Then
hname(i) = 32
End If
Next i
getname = Trim$(StrConv(hname, vbUnicode))
End Function
Private Sub Command2_Click()
Dim name As String
name = getname(Text2.Text)
If name = "" Then
name = "此地址没有域名"
End If
Text1.Text = name
End Sub