源码是老外的，俺做了点修改，写成了dll
方法：
Public Function GetDNSinfo() As String
获取dns信息
Public Function MX_Query(DNS_Addr As String, ByVal Domain_Addr As String) As String
获取mx最佳记录，
dns_addr,域名解析服务器，可以用getdnsinfo获取，也可以用nslookup命令
domain_addr，想要获取邮件服务器的域名，如163.com ,hotmail.com
http://www.aspcdrom.com/down/mxquery.rar
VERSION 1.0 CLASS
BEGIN
MultiUse = -1 'True
Persistable = 0 'NotPersistable
DataBindingBehavior = 0 'vbNone
DataSourceBehavior = 0 'vbNone
MTSTransactionMode = 0 'NotAnMTSObject
END
Attribute VB_Name = "mxquery"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = True
Attribute VB_PredeclaredId = False
Attribute VB_Exposed = True
Option Explicit
Private WithEvents objWinSock As MSWinsockLib.Winsock
Attribute objWinSock.VB_VarHelpID = -1
Private Const ERROR_BUFFER_OVERFLOW = 111
Private DNSrecieved As Boolean
Private dnsReply() As Byte
Private Declare Function GetNetworkParams Lib "IPHlpApi" (FixedInfo As Any, pOutBufLen As Long) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)
Private Declare Sub MemCopy Lib "kernel32" Alias "RtlMoveMemory" (Dest As Any, Src As Any, ByVal cb&)
Private Declare Function htons Lib "wsock32.dll" (ByVal hostshort As Long) As Integer
Private Declare Function ntohs Lib "wsock32.dll" (ByVal netshort As Long) As Integer
Private Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long)
Private Const DNS_RECURSION As Byte = 1
Private Const MAX_HOSTNAME_LEN = 132
Private Const MAX_DOMAIN_NAME_LEN = 132
Private Const MAX_SCOPE_ID_LEN = 260
Private Const MAX_ADAPTER_NAME_LENGTH = 260
Private Const MAX_ADAPTER_ADDRESS_LENGTH = 8
Private Const MAX_ADAPTER_DESCRIPTION_LENGTH = 132
Private Type IP_ADDR_STRING
Next As Long
IpAddress As String * 16
IpMask As String * 16
Context As Long
End Type
Private Type FIXED_INFO
HostName As String * MAX_HOSTNAME_LEN
DomainName As String * MAX_DOMAIN_NAME_LEN
CurrentDnsServer As Long
DnsServerList As IP_ADDR_STRING
NodeType As Long
ScopeId As String * MAX_SCOPE_ID_LEN
EnableRouting As Long
EnableProxy As Long
EnableDns As Long
End Type
Private Type DNS_HEADER
qryID As Integer
options As Byte
response As Byte
qdcount As Integer
ancount As Integer
nscount As Integer
arcount As Integer
End Type
Private 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
Private Const hostent_size = 16
Private Type servent
s_name As Long
s_aliases As Long
s_port As Integer
s_proto As Long
End Type
Private Function MakeQName(sDomain As String) As String
Dim iQCount As Integer ' Character count (between dots)
Dim iNdx As Integer ' Index into sDomain string
Dim iCount As Integer ' Total chars in sDomain string
Dim sQName As String ' QNAME string
Dim sDotName As String ' Temp string for chars between dots
Dim sChar As String ' Single char from sDomain string
iNdx = 1
iQCount = 0
iCount = Len(sDomain)
' While we haven't hit end-of-string
While (iNdx <= iCount)
' Read a single char from our domain
sChar = Mid(sDomain, iNdx, 1)
' If the char is a dot, then put our character count and the part of the string
If (sChar = ".") Then
sQName = sQName & Chr(iQCount) & sDotName
iQCount = 0
sDotName = ""
Else
sDotName = sDotName + sChar
iQCount = iQCount + 1
End If
iNdx = iNdx + 1
Wend
sQName = sQName & Chr(iQCount) & sDotName
MakeQName = sQName
End Function
Private Sub ParseName(dnsReply() As Byte, iNdx As Integer, sName As String)
Dim iCompress As Integer ' Compression index (index into original buffer)
Dim iChCount As Integer ' Character count (number of chars to read from buffer)
' While we didn't encounter a null char (end-of-string specifier)
While (dnsReply(iNdx) <> 0)
' Read the next character in the stream (length specifier)
iChCount = dnsReply(iNdx)
' If our length specifier is 192 (0xc0) we have a compressed string
If (iChCount = 192) Then
' Read the location of the rest of the string (offset into buffer)
iCompress = dnsReply(iNdx + 1)
' Call ourself again, this time with the offset of the compressed string
ParseName dnsReply(), iCompress, sName
' Step over the compression indicator and compression index
iNdx = iNdx + 2
' After a compressed string, we are done
Exit Sub
End If
' Move to next char
iNdx = iNdx + 1
' While we should still be reading chars
While (iChCount)
' add the char to our string
sName = sName + Chr(dnsReply(iNdx))
iChCount = iChCount - 1
iNdx = iNdx + 1
Wend
' If the next char isn't null then the string continues, so add the dot
If (dnsReply(iNdx) <> 0) Then sName = sName + "."
Wend
End Sub
Private Function GetMXName(dnsReply() As Byte, iNdx As Integer, iAnCount As Integer) As String
Dim iChCount As Integer ' Character counter
Dim sTemp As String ' Holds original query string
Dim iMXLen As Integer
Dim iBestPref As Integer ' Holds the "best" preference number (lowest)
Dim sBestMX As String ' Holds the "best" MX record (the one with the lowest preference)
iBestPref = -1
ParseName dnsReply(), iNdx, sTemp
' Step over null
iNdx = iNdx + 2
' Step over 6 bytes (not sure what the 6 bytes are, but all other
' documentation shows steping over these 6 bytes)
iNdx = iNdx + 6
On Error Resume Next
While (iAnCount)
' Check to make sure we received an MX record
If (dnsReply(iNdx) = 15) Then
Dim sName As String
Dim iPref As Integer
sName = ""
' Step over the last half of the integer that specifies the record type (1 byte)
' Step over the RR Type, RR Class, TTL (3 integers - 6 bytes)
iNdx = iNdx + 1 + 6
' Read the MX data length specifier
' (not needed, hence why it's commented out)
MemCopy iMXLen, dnsReply(iNdx), 2
iMXLen = ntohs(iMXLen)
' Step over the MX data length specifier (1 integer - 2 bytes)
iNdx = iNdx + 2
MemCopy iPref, dnsReply(iNdx), 2
iPref = ntohs(iPref)
' Step over the MX preference value (1 integer - 2 bytes)
iNdx = iNdx + 2
' Have to step through the byte-stream, looking for 0xc0 or 192 (compression char)
Dim iNdx2 As Integer
iNdx2 = iNdx
ParseName dnsReply(), iNdx2, sName
If (iBestPref = -1 Or iPref < iBestPref) Then
iBestPref = iPref
sBestMX = sName
End If
iNdx = iNdx + iMXLen + 1
' Step over 3 useless bytes
'iNdx = iNdx + 3
Else
GetMXName = sBestMX
Exit Function
End If
iAnCount = iAnCount - 1
Wend
GetMXName = sBestMX
End Function
Public Function GetDNSinfo() As String
Dim error As Long
Dim FixedInfoSize As Long
Dim strDNS As String
Dim FixedInfo As FIXED_INFO
Dim Buffer As IP_ADDR_STRING
Dim FixedInfoBuffer() As Byte
FixedInfoSize = 0
error = GetNetworkParams(ByVal 0&, FixedInfoSize)
If error <> 0 Then
If error <> ERROR_BUFFER_OVERFLOW Then
MsgBox "GetNetworkParams sizing failed with error: " & error
Exit Function
End If
End If
ReDim FixedInfoBuffer(FixedInfoSize - 1)
error = GetNetworkParams(FixedInfoBuffer(0), FixedInfoSize)
If error = 0 Then
CopyMemory FixedInfo, FixedInfoBuffer(0), Len(FixedInfo)
strDNS = FixedInfo.DnsServerList.IpAddress
strDNS = Replace(strDNS, vbCr, "")
strDNS = Replace(strDNS, vbLf, "")
strDNS = Replace(strDNS, vbNullChar, "")
strDNS = Trim(strDNS)
GetDNSinfo = strDNS
End If
End Function
Private Sub Class_Initialize()
Set objWinSock = New MSWinsockLib.Winsock
objWinSock.Protocol = sckUDPProtocol
objWinSock.RemotePort = 53
End Sub
Private Sub Class_Terminate()
Set objWinSock = Nothing '
End Sub
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
''class
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Private Sub objWinSock_Error(ByVal Number As Integer, Description As String, ByVal Scode As Long, ByVal Source As String, ByVal HelpFile As String, ByVal HelpContext As Long, CancelDisplay As Boolean)
Debug.Print Description
End Sub
Private Sub objWinSock_DataArrival(ByVal bytesTotal As Long)
DNSrecieved = True
ReDim dnsReply(bytesTotal) As Byte
objWinSock.GetData dnsReply, vbArray + vbByte
End Sub
Public Function MX_Query(DNS_Addr As String, ByVal Domain_Addr As String) As String
Dim IpAddr As Long
Dim iRC As Integer
Dim dnsHead As DNS_HEADER
Dim iSock As Integer
' Set the DNS parameters
dnsHead.qryID = htons(&H11DF)
dnsHead.options = DNS_RECURSION
dnsHead.qdcount = htons(1)
dnsHead.ancount = 0
dnsHead.nscount = 0
dnsHead.arcount = 0
' Query Variables
Dim dnsQuery() As Byte
Dim sQName As String
Dim dnsQueryNdx As Integer
Dim iTemp As Integer
Dim iNdx As Integer
dnsQueryNdx = 0
ReDim dnsQuery(4000)
' Setup the dns structure to send the query in
' First goes the DNS header information
MemCopy dnsQuery(dnsQueryNdx), dnsHead, 12
dnsQueryNdx = dnsQueryNdx + 12
' Then the domain name (as a QNAME)
sQName = MakeQName(Domain_Addr)
iNdx = 0
While (iNdx < Len(sQName))
dnsQuery(dnsQueryNdx + iNdx) = Asc(Mid(sQName, iNdx + 1, 1))
iNdx = iNdx + 1
Wend
dnsQueryNdx = dnsQueryNdx + Len(sQName)
' Null terminate the string
dnsQuery(dnsQueryNdx) = &H0
dnsQueryNdx = dnsQueryNdx + 1
' The type of query (15 means MX query)
iTemp = htons(15)
MemCopy dnsQuery(dnsQueryNdx), iTemp, Len(iTemp)
dnsQueryNdx = dnsQueryNdx + Len(iTemp)
' The class of query (1 means INET)
iTemp = htons(1)
MemCopy dnsQuery(dnsQueryNdx), iTemp, Len(iTemp)
dnsQueryNdx = dnsQueryNdx + Len(iTemp)
On Error Resume Next
ReDim Preserve dnsQuery(dnsQueryNdx - 1)
' Send the query to the DNS server
objWinSock.RemoteHost = DNS_Addr
DNSrecieved = False
objWinSock.SendData dnsQuery
If WaitUntilTrue(DNSrecieved, 60) = False Then
'MX_Query = ""
Exit Function
End If
Dim iAnCount As Integer
' Get the number of answers
MemCopy iAnCount, dnsReply(6), 2
iAnCount = ntohs(iAnCount)
' Parse the answer buffer
MX_Query = Trim(GetMXName(dnsReply(), 12, iAnCount))
End Function
Private Function WaitUntilTrue(ByRef Flag As Boolean, ByVal SecondsToWait As Long) As Boolean
Dim fStart As Single
Dim fTimetoQuit As Single
fStart = Timer
' Deal with timer being reset at Midnight
If fStart + SecondsToWait < 86400 Then
fTimetoQuit = fStart + SecondsToWait
Else
fTimetoQuit = (fStart - 86400) + SecondsToWait
End If
Do Until Flag = True
If Timer >= fTimetoQuit Then
WaitUntilTrue = Flag
Exit Function
End If
DoEvents
Sleep (10)
Loop
WaitUntilTrue = Flag
End Function
极品源码，无限精彩，尽在 http://www.aspcdrom.com
