' flags for InternetOpen():
Private Const INTERNET_FLAG_ASYNC = &H10000000              ' this request is asynchronous (where supported)
Private Declare Sub InternetSetStatusCallback Lib "wininet.dll" (ByVal hInternetSession As Long, ByVal lpfnCallBack As Long)

Public Function SendAPIRequest2(ByVal strUrl As String) As String
    Dim hOpen As Long, hFile As Long
    Dim Ret As Long, sBuffer As String *  128 
    Dim iResult As Integer, sData As String
    hOpen = InternetOpen("VB Program",  1 , vbNullString, vbNullString, INTERNET_FLAG_ASYNC)
    If hOpen =  0  Then
        MsgBox "Error opening Internet connection"
        Exit Function
    End If
    InternetSetStatusCallback hOpen, AddressOf MyCallBack
.....
Sub MyCallBack( _
  ByVal hInternet As Long, _
  ByVal dwContext As Long, _
  ByVal dwInternetStatus As Long, _
  ByVal pbStatusInformation As Long, _
  ByVal dwStatusInformationLength As Long)

    ' Callback routine implementation.
    Debug.Print "Status: " & dwInternetStatus
End Sub

Private Const szSvrName As String = "www.myserver.com"

Private Sub Command1_Click()
     MsgBox SendRequest("/downloads/file.txt")
End Sub

  Public Declare Function InternetReadFile Lib "wininet.dll" ( _
      ByVal hFile As Long, _
      ByVal sBuffer As Long, _
      ByVal lNumBytesToRead As Long, _
      lNumberOfBytesRead As Long) As Integer

Private Type INTERNET_BUFFERS
  dwStructSize    As Long   'DWORD              // Unsigned long integer value used for API versioning. This is set to the size of the INTERNET_BUFFERS structure.
  Next            As Long   'INTERNET_BUFFERS * // Address of the next INTERNET_BUFFERS structure. (Use the VB "VarPtr" function to get the address of the INTERNET_BUFFERS variable to pass to this member)
  lpcszHeader     As String 'LPCTSTR            // Address of a string value that contains the headers. This value can be NULL.
  dwHeadersLength As Long   'DWORD              // Unsigned long integer value that contains the length of the headers, in TCHARs, if lpcszHeader is not NULL.
  dwHeadersTotal  As Long   'DWORD              // Unsigned long integer value that contains the size of the headers if there is not enough memory in the buffer.
  lpvBuffer       As Long   'LPVOID             // Address of the data buffer.
  dwBufferLength  As Long   'DWORD              // Unsigned long integer value that contains the length of the buffer, in TCHARs, if lpvBuffer is not NULL.
  dwBufferTotal   As Long   'DWORD              // Unsigned long integer value that contains the total size of the resource.
  dwOffsetLow     As Long   'DWORD              // Unsigned long integer value that is used for read ranges.
  dwOffsetHigh    As Long   'DWORD              // Unsigned long integer value that is used for read ranges.
End Type

' Constants - InternetReadFileEx.dwFlags
Private Const IRF_ASYNC = &H1       ' Undocumented
Private Const IRF_SYNC = &H4        ' Undocumented
Private Const IRF_USE_CONTEXT = &H8 ' Undocumented
Private Const IRF_NO_WAIT = &H8     ' Do not wait for data. If there is data available, the function returns either the amount of data requested or the amount of data available (whichever is smaller).


Private Declare Function InternetReadFileEx Lib "WININET.DLL" Alias "InternetReadFileExA" (ByVal hFile As Long, ByRef lpBuffersOut As INTERNET_BUFFERS, ByVal dwFlags As Long, ByVal dwContext As Long) As Long   'BOOL

Private Sub InternetCallbackFunc(ByVal hInternet As Long, ByVal dwContext As Long, _
                                                          ByVal dwInternetStatus As Long, _
                                                          ByVal pbStatusInformation As Long, _
                                                          ByVal dwStatusInformationLength As Long)
...
    Const BufLen As Long =  1024 
    Dim OutBuffer As INTERNET_BUFFERS
    Dim Buffer( 0  To BufLen -  1 ) As Byte
    ' Set up return buffer structure
    OutBuffer.dwStructSize = Len(OutBuffer)
    OutBuffer.dwBufferLength = BufLen
    OutBuffer.lpvBuffer = VarPtr(Buffer( 0 ))
...
                    Do Until InternetReadFileEx(hInternet, OutBuffer, IRF_ASYNC,  0 &) =  0 & '???
                        'If lng = 0& Then
                        If OutBuffer.dwBufferLength =  0 & Then
                            stContext.dwExitFlag = vbNull
                            Exit Do
                        Else
                            'sOutBuffer = sOutBuffer & Left$(szTmpBuffer, lng)
                            sOutBuffer = sOutBuffer & Left$(OutBuffer.dwBufferTotal, OutBuffer.dwBufferLength) '???
                        End If
                    Loop

Private Sub cmdGet_Click()
    Inet1.Execute txtFile.Text, "GET"
End Sub

Private Sub Inet1_StateChanged(ByVal State As Integer)
Dim var_data As Variant
Dim str_data As String
Debug.Print State
    If State = icResponseCompleted Then
        ' Get the first chunk.
        var_data = Inet1.GetChunk( 1024 , icString)
        str_data = str_data & var_data

        ' Get the rest of the chunks.
        Do
            DoEvents
            var_data = Inet1.GetChunk( 1024 , icString)
            If Len(var_data) =  0  Then Exit Do
            str_data = str_data & var_data
        Loop

        txtResults.Text = str_data
    End If
End Sub

Private Sub Command1_Click()
     MsgBox SendRequest("/downloads/file.txt")
End Sub

Private Sub Command1_Click()
     MsgBox SendRequest("/downloads/file.txt")
End Sub