Option Explicit
Private Const NI_MAXHOST = 1025
Private Const NI_MAXSERV = 32
Private Const AF_INET = 2                      ' internetwork: UDP, TCP, etc.
 
Private Const WS_VERSION_REQD     As Long = &H202
Private Const MAX_WSADescription = 256
Private Const MAX_WSASYSStatus = 128
 
Private Type WSADATA
    wVersion      As Integer
    wHighVersion  As Integer
    szDescription(0 To MAX_WSADescription)   As Byte
    szSystemStatus(0 To MAX_WSASYSStatus)    As Byte
    wMaxSockets   As Integer
    wMaxUDPDG     As Integer
    dwVendorInfo  As Long
End Type
 
Private Type sockaddr_in
    sin_family       As Integer
    sin_port         As Integer
    sin_addr         As Long
    sin_zero(1 To 8) As Byte
End Type
 
 
Private Const NI_NOFQDN = &H1&         ' Only return nodename portion for local 
' hosts
 
Private Const NI_NUMERICHOST = &H2&     ' Return numeric form of the host's _
  address */
Private Const NI_NAMEREQD = &H4&        ' Error if the host's name not in DNS */
Private Const NI_NUMERICSERV = &H8&     ' Return numeric form of the service ( 
' port #) */
Private Const NI_DGRAM = &H10&          ' Service is a datagram service */
 
Private Declare Function getnameinfo Lib "Ws2_32" (ByRef sa As sockaddr_in, _
  ByVal salen As Long, ByVal Host As String, ByVal hostlen As Long, ByVal serv _
  As String, ByVal servlen As Long, ByVal flags As Long) As Long
Private Declare Function Ipv4ToLong Lib "ws2_32.dll" Alias "inet_addr" (ByVal _
cp As String) As Long
Private Declare Function htons Lib "ws2_32.dll" (ByVal hostshort As Integer) As _
Integer
Private Declare Function WSAStartup Lib "wsock32.dll" (ByVal wVersionRequired _
As Long, lpWSADATA As WSADATA) As Long
Private Declare Function WSACleanup Lib "wsock32.dll" () As Long
Private Declare Function WSAGetLastError Lib "wsock32.dll" () As Long
 
Public Function VB_getnameinfo(IP As String, Port As Long, HostName As String, _
  ServiceName As String) As Long
' Declare and initialize variables
Dim sa As sockaddr_in
Dim RetCode As Long
Dim Host As String * NI_MAXHOST
Dim Service As String * NI_MAXSERV
Dim WSAD As WSADATA
RetCode = WSAStartup(WS_VERSION_REQD, WSAD)
If RetCode <> 0 Then
   VB_getnameinfo = False
   Exit Function
End If
' -----------------------------------------
' Set up sockaddr_in structure which is passedto the getnameinfo function
sa.sin_family = AF_INET
sa.sin_addr = Ipv4ToLong(IP)
sa.sin_port = htons(Port)
' -----------------------------------------
' Call getnameinfo
RetCode = getnameinfo(sa, Len(sa), Host, Len(Host), vbNull, 0, NI_NUMERICSERV)
If RetCode = 0 Then
   HostName = Left$(Host, InStr(1, Host, Chr(0)) - 1)
   ServiceName = Left$(Service, InStr(1, Host, Chr(0)) - 1)
End If
WSACleanup
VB_getnameinfo = RetCode
End Function