vb6 implementation for icmpsendecho2

Question

I'm trying to implement a Ping program in vb6 which works for both IPv4 & IPv6 addresses. The IPv4 implementation uses IcmpSendEcho which is working fine, but the IPv6 implementation uses Icmp6SendEcho2 and I'm having a lot of difficulty getting it to work.

The function call works fine and it does not error out but the return value is always 0, and GetLastError returns 0 indicating that no errors occurred

https://msdn.microsoft.com/en-us/library/windows/desktop/aa366041(v=vs.85).aspx

The process I follow is as follows:

• Load the windows sockets dll by calling WSAStartup
• Open a port handle via a call to Icmp6CreateHandle
• Send a ICMP ECHO message via a call to Icmp6SendEcho2 and analyze the response
• close the port handle by calling IcmpCloseHandle
• Unload dll by calling WSACleanup

The definition of Icmp6SendEcho2 is as follows

Private Declare Function Icmp6SendEcho2 Lib "Iphlpapi.dll" _
    (ByVal IcmpHandle As Long, _
    ByVal EventtoRaise As Long, _
    ByVal ApcRoutine As Long, _
    ByVal ApcContext As Long, _
    ByVal SourceAddressPointer As Long, _
    ByVal DestinationAddressPointer As Long, _
    ByVal RequestData As String, _
    ByVal RequestSize As Long, _
    ByVal RequestOptions As Long, _
    ReplyBuffer As ICMPV6_ECHO_REPLY, _
    ByVal ReplySize As Long, _
    ByVal timeOut As Long) As Long

Where ICMPV6_ECHO_REPLY is defined as follows

Private Type ICMPV6_ECHO_REPLY
    Address As IPV6_ADDRESS
    Status As Long
    RoundTripTime As Long
End Type

Private Type IPV6_ADDRESS
    sin6_port As Integer
    sin6_flowinfo As Long
    sin6_addr(1 To 8) As Integer
    sin6_scope_id As Long
End Type

The call to Icmp6SendEcho2 is made as follows

lPingResponse = Icmp6SendEcho2(lPortHandle, 0, 0, 0, VarPtr(SourceAddress), VarPtr(DestinationAddress), sMessage, Len(sMessage), 0, Reply, Len(Reply), timeOut)

I used the following link for implementing Ping for IPv4 https://support.microsoft.com/en-us/kb/300197

Any help would be awesome

Nish

Answer 1

The issue was associated with there not being a sufficient buffer to get the response. Changing the response structure to something like this did the trick

Private Type ICMPV6_ECHO_REPLY
  Address As IPV6_ADDRESS
  Status As Long
  RoundTripTime As Long
  data(0 To 1023) As Byte
End Type