Зная IP компа, как определить, находится ли он в сети - VB

''*******************************************************************
''   PingVB
''
''   This application implements a TCP/IP network ping
''   using the ICMP.DLL provided as part of Windows 95 and
''   Windows NT.
''   IP_STATUS codes returned from IP APIs
''
''*******************************************************************
Private Const IP_STATUS_BASE = 11000
 
Private Const IP_SUCCESS = 0
Private Const IP_BUF_TOO_SMALL = (11000 + 1)
Private Const IP_DEST_NET_UNREACHABLE = (11000 + 2)
Private Const IP_DEST_HOST_UNREACHABLE = (11000 + 3)
Private Const IP_DEST_PROT_UNREACHABLE = (11000 + 4)
Private Const IP_DEST_PORT_UNREACHABLE = (11000 + 5)
Private Const IP_NO_RESOURCES = (11000 + 6)
Private Const IP_BAD_OPTION = (11000 + 7)
Private Const IP_HW_ERROR = (11000 + 8)
Private Const IP_PACKET_TOO_BIG = (11000 + 9)
Private Const IP_REQ_TIMED_OUT = (11000 + 10)
Private Const IP_BAD_REQ = (11000 + 11)
Private Const IP_BAD_ROUTE = (11000 + 12)
Private Const IP_TTL_EXPIRED_TRANSIT = (11000 + 13)
Private Const IP_TTL_EXPIRED_REASSEM = (11000 + 14)
Private Const IP_PARAM_PROBLEM = (11000 + 15)
Private Const IP_SOURCE_QUENCH = (11000 + 16)
Private Const IP_OPTION_TOO_BIG = (11000 + 17)
Private Const IP_BAD_DESTINATION = (11000 + 18)
''
''   The next group are status codes passed up on status indications to
''   transport layer protocols.
''
Private Const IP_ADDR_DELETED = (11000 + 19)
Private Const IP_SPEC_MTU_CHANGE = (11000 + 20)
Private Const IP_MTU_CHANGE = (11000 + 21)
Private Const IP_UNLOAD = (11000 + 22)
Private Const IP_ADDR_ADDED = (11000 + 23)
 
Private Const IP_GENERAL_FAILURE = (11000 + 50)
Private Const MAX_IP_STATUS = 11000 + 50
Private Const IP_PENDING = (11000 + 255)
 
''   option information for network ping, we don''t implement these here as this is
''   a simple sample (simon says).
Private Type ip_option_information
    Ttl             As Byte     ''Time To Live
    Tos             As Byte     ''Type Of Service
    Flags           As Byte     ''IP header flags
    OptionsSize     As Byte     ''Size in bytes of options data
    OptionsData     As Long     ''Pointer to options data
End Type
 
''   structure that is returned from the ping to give status and error information
Private Type icmp_echo_reply
    Address         As Long             ''Replying address
    Status          As Long             ''Reply IP_STATUS, values as defined above
    RoundTripTime   As Long             ''RTT in milliseconds
    DataSize        As Integer          ''Reply data size in bytes
    Reserved        As Integer          ''Reserved for system use
    DataPointer     As Long             ''Pointer to the reply data
    Options         As ip_option_information    ''Reply options
    Data            As String * 250     ''Reply data which should be a copy of the string sent, NULL terminated
                                        '' this field length should be large enough to contain the string sent
End Type
 
''   declares for function to be used from icmp.dll
Private Declare Function IcmpCreateFile Lib 'icmp.dll' () As Long
Private Declare Function IcmpCloseHandle Lib 'icmp.dll' (ByVal IcmpHandle As Long) As Long
Private Declare Function IcmpSendEcho Lib 'icmp.dll' (ByVal IcmpHandle As Long, _
                                                    ByVal DestinationAddress As Long, _
                                                    ByVal RequestData As String, _
                                                    ByVal RequestSize As Integer, _
                                                    RequestOptions As ip_option_information, _
                                                    R   4 numbers, flip them around and make
''   a long by shifting all the parts into the correct byte. We
''   do it here by making a hex string and converting it to a long.
''   Not pretty but it works (most of the time<g>).
''
''   When we get in 'a.b.c.d' what we want out is Val(&Hddccbbaa).
''
 
Function ConvertIPAddressToLong(strAddress As String) As Long
 
    Dim strTemp             As String
    Dim lAddress            As Long
    Dim iValCount           As Integer
    Dim lDotValues(1 To 4)  As String
    
    '' set up the initial storage and counter
    strTemp = strAddress
    iValCount = 0
    
    '' keep going while we still have dots in the string
    While InStr(strTemp, '.') > 0
        iValCount = iValCount + 1   '' count the number
        lDotValues(iValCount) = Mid(strTemp, 1, InStr(strTemp, '.') - 1)    '' pick it off and convert it
        strTemp = Mid(strTemp, InStr(strTemp, '.') + 1) '' chop off the number and the dot
        Wend
        
    '' the string only has the last number in it now
    iValCount = iValCount + 1
    lDotValues(iValCount) = strTemp
    
    '' if we didn''t get four pieces then the IP address is no good
    If iValCount <> 4 Then
        ConvertIPAddressToLong = 0
        Exit Function
        End If
        
    ''   take the four value, hex them, pad to 2 digits, make a hex
    ''   string and then convert the whole mess to a long for returning
    lAddress = Val('&H' & Right('00' & Hex(lDotValues(4)), 2) & _
                Right('00' & Hex(lDotValues(3)), 2) & _
                Right('00' & Hex(lDotValues(2)), 2) & _
                Right('00' & Hex(lDotValues(1)), 2))
                
    ''   set the return value
    ConvertIPAddressToLong = lAddress
    
End Function