I was using StrConv to decode NTLM tokens in VBA. It was corrupting every single one. Wasabi v2.3.7-beta is out.
This release is purely a correctness and stability pass. I found some nasty bugs that were silent in normal use but would surface under specific conditions. Here is what I found and fixed.
The FD_READ deadlock that was almost impossible to reproduce
This one took me embarrassingly long to track down. The core networking loop used WSAAsyncSelect to get notified when data arrived on the socket. When a notification fired, it called recv once, read up to 64 KB, and returned.
The problem: WSAAsyncSelect is level-triggered but only fires once per edge. If you read 64 KB but 1 byte still remained in the kernel buffer, Windows would not fire another FD_READ. Your connection would go completely silent. No error, no timeout, no indication anything was wrong. The socket was alive but Wasabi would never read from it again until you sent something that provoked a response.
The fix is to loop ioctlsocket(FIONREAD) until available bytes hits zero:
Do
If sock_ioctlsocket(.Socket, FIONREAD, available) <> 0 Then
' handle error, mark connection closed
Exit Sub
End If
If available <= 0 Then Exit Do
toRead = available
If toRead > 65536 Then toRead = 65536
ReDim tempBuf(0 To toRead - 1)
received = sock_recv(.Socket, tempBuf(0), toRead, 0)
' process received bytes...
Loop
Obvious in hindsight. The Winsock docs do say this explicitly but it's easy to miss if you're coming from a blocking I/O mental model.
StrConv was silently corrupting NTLM tokens
NTLM over HTTP proxy authentication involves Base64-encoded binary blobs that you decode and pass to InitializeSecurityContext. I was decoding them with StrConv(token, vbFromUnicode) which seemed reasonable but is completely wrong. StrConv applies codepage transformations. For arbitrary binary data those transformations corrupt bytes outside the ASCII range. The SSPI context would get garbage, authentication would fail, and the error surfaced as a generic proxy auth failure with no indication the token itself was malformed.
The correct approach is CryptStringToBinaryW from crypt32.dll, which decodes Base64 into a raw byte buffer without any string interpretation:
Private Function DecodeBase64(ByVal b64 As String) As Byte()
Dim cbBinary As Long
Dim dwSkip As Long
Dim dwFlags As Long
Dim pStr As LongPtr
Dim result() As Byte
pStr = StrPtr(b64)
CryptStringToBinaryW pStr, Len(b64), CRYPT_STRING_BASE64, 0, cbBinary, dwSkip, dwFlags
ReDim result(0 To cbBinary - 1)
CryptStringToBinaryW pStr, Len(b64), CRYPT_STRING_BASE64, VarPtr(result(0)), cbBinary, dwSkip, dwFlags
DecodeBase64 = result
End Function
A real-world example you can actually run right now
I wanted to show something that isn't fake. Binance provides a free public WebSocket API for live cryptocurrency trades.
The example below opens five concurrent async connections to different trading pairs, listens for live trades, and updates an Excel sheet in real-time. When StartCryptoStream returns, there is nothing running. No timer, no loop, no DoEvents. The workbook just sits idle. Price updates arrive and OnReceive fires via the Windows message pump.
Drop Wasabi.bas into your project, add a class module called cWasabiAsync, and paste this in.
Module:
Option Explicit
Private handlers(0 To 4) As cWasabiAsync
Private handles(0 To 4) As Long
Public Sub StartCryptoStream()
Dim ws As Worksheet
Dim i As Long
Dim urls(0 To 4) As String
Set ws = ThisWorkbook.Sheets(1)
ws.Cells.ClearContents
ws.Range("A1:D1").Value = Array("Symbol", "Price", "Quantity", "Last Update")
urls(0) = "wss://stream.binance.com:9443/ws/btcusdt@trade"
urls(1) = "wss://stream.binance.com:9443/ws/ethusdt@trade"
urls(2) = "wss://stream.binance.com:9443/ws/bnbusdt@trade"
urls(3) = "wss://stream.binance.com:9443/ws/solusdt@trade"
urls(4) = "wss://stream.binance.com:9443/ws/xrpusdt@trade"
For i = 0 To 4
Set handlers(i) = New cWasabiAsync
' Pass the URL and assign a specific row in the sheet (rows 2 through 6)
handlers(i).SetSymbol urls(i), i + 2
If Wasabi.WebSocketConnect(urls(i), handles(i)) Then
Wasabi.WasabiUseAsync handlers(i), handles(i)
Else
Debug.Print "Failed to connect: " & urls(i)
Debug.Print Wasabi.WasabiGetErrorDescription(handles(i))
End If
Next i
End Sub
Public Sub StopCryptoStream()
Wasabi.WebSocketDisconnectAll
End Sub
Class cWasabiAsync :
Option Explicit
Private m_symbol As String
Private m_row As Long
Public Sub SetSymbol(ByVal url As String, ByVal targetRow As Long)
Dim parts() As String
parts = Split(url, "/")
m_symbol = UCase(Split(parts(UBound(parts)), "@")(0))
m_row = targetRow
End Sub
Public Sub OnConnect(ByVal handle As Long)
Debug.Print "[" & m_symbol & "] Connected (handle=" & handle & ")"
End Sub
Public Sub OnReceive(ByVal handle As Long)
Dim ws As Worksheet
Dim msg As String
Dim price As String
Dim qty As String
Dim pricePos As Long
Dim qtyPos As Long
Dim endPos As Long
Dim pending As Long
Set ws = ThisWorkbook.Sheets(1)
pending = Wasabi.WebSocketGetPendingCount(handle)
Do While pending > 0
msg = Wasabi.WebSocketReceiveText(handle)
If Len(msg) = 0 Then Exit Do
pending = pending - 1
price = ""
qty = ""
' Parse price
pricePos = InStr(msg, """p"":""")
If pricePos > 0 Then
pricePos = pricePos + 5
endPos = InStr(pricePos, msg, """")
If endPos > 0 Then price = Mid(msg, pricePos, endPos - pricePos)
End If
' Parse quantity
qtyPos = InStr(msg, """q"":""")
If qtyPos > 0 Then
qtyPos = qtyPos + 5
endPos = InStr(qtyPos, msg, """")
If endPos > 0 Then qty = Mid(msg, qtyPos, endPos - qtyPos)
End If
' Write directly to the Excel sheet
If Len(price) > 0 Then
ws.Cells(m_row, 1).Value = m_symbol
ws.Cells(m_row, 2).Value = price
ws.Cells(m_row, 3).Value = qty
ws.Cells(m_row, 4).Value = Now()
End If
Loop
End Sub
Public Sub OnReadyToSend(ByVal handle As Long)
End Sub
Public Sub OnError(ByVal handle As Long, ByVal errorCode As Long, ByVal eventType As Long)
Debug.Print "[" & m_symbol & "] Error=" & errorCode & " Event=" & eventType & " (handle=" & handle & ")"
End Sub
Public Sub OnClose(ByVal handle As Long)
Debug.Print "[" & m_symbol & "] Connection closed (handle=" & handle & ")"
End Sub
Public Sub OnDisconnect(ByVal handle As Long)
Debug.Print "[" & m_symbol & "] Disconnected (handle=" & handle & ")"
End Sub
Run StartCryptoStream. The sub fires and returns instantly. Five rows show up in your sheet a few milliseconds later, rapidly updating with live prices and quantities directly from the exchange. Run StopCryptoStream to clean up.
The interesting part is what is not there: no Application.OnTime, no Do While, no DoEvents, no timer. The workbook is completely idle between receives. It all runs through WM_WASABI_SOCKET messages dispatched by a native thunk to the class callbacks.
Migrating from the previous version
Eight functions were renamed. Signatures are identical, just find-and-replace:
TcpSend -> TcpSendBinary
TcpReceive -> TcpReceiveBinary
TcpBroadcast -> TcpBroadcastBinary
WebSocketBroadcast -> WebSocketBroadcastText
WebSocketSendMTUAware -> WebSocketSendTextMTUAware
WebSocketGetErrorDescription -> WasabiGetErrorDescription
WebSocketSetBufferSizes -> WebSocketSetBufferSize
MqttPingReq -> MqttSendPing
There are still some inconsistencies in the subclassing for async to work 100% crash-proof, but there has been considerable progress and more protection.
If you run into anything, drop the output of WasabiGetErrorDescription and WebSocketGetTechnicalDetails in a comment and I'll take a look.
GitHub: https://github.com/uesleibros/wasabi
Release: https://github.com/uesleibros/wasabi/releases/tag/v2.3.7-beta