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fix(battle-node): strip/prepend EIO3 type byte on binary WS frames

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Engine.IO v3 frames over WebSocket prepend the packet-type byte (0x04
for Message) to BINARY frames, the binary analog of the leading digit
on text frames. The real client honors this and our session was
treating the entire binary frame as the Socket.IO attachment payload —
the msgpack decoder saw 0x04 as a positive fixint and failed
deserialization on every inbound msg event.

Symmetric fix: strip 0x04 from inbound binary frames in
BattleSession.RunAsync, prepend 0x04 to outbound binary frames in
EncodeAndSendAsync. RawSocketIoTestClient gets the same on both
directions so the integration test still exercises the same wire
shape as a real client.

Caught during v1 smoke walkthrough, after the WS upgrade started
succeeding (101 Switching Protocols).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
gamer147
2026-06-01 01:48:52 -04:00
parent ccc9b41473
commit cc32223d7d
2 changed files with 31 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
SVSim.BattleNode/Sessions/BattleSession.cs
View File

@@ -72,7 +72,15 @@ public sealed class BattleSession
else
{
// Binary frame — an attachment for a pending binary event.
pendingAttachments.Add(msg.Value.Bytes);
// Engine.IO v3 prefixes binary WS frames with the packet-type byte
// (0x04 = Message), analogous to the leading digit on text frames.
// Strip it before treating the rest as the Socket.IO attachment payload.
var bin = msg.Value.Bytes;
if (bin.Length > 0 && bin[0] == (byte)EngineIoPacketType.Message)
{
bin = bin.AsSpan(1).ToArray();
}
pendingAttachments.Add(bin);
if (pendingFrame is not null && pendingAttachments.Count == pendingFrame.AttachmentCount)
{
var assembled = pendingFrame.WithAttachments(pendingAttachments.ToArray());
@@ -248,7 +256,14 @@ public sealed class BattleSession
var eioText = $"{(int)EngineIoPacketType.Message}{text}";
await SendTextAsync(eioText, CancellationToken.None);
foreach (var bin in bins)
await _ws.SendAsync(bin, WebSocketMessageType.Binary, endOfMessage: true, CancellationToken.None);
{
// Engine.IO v3 binary frames are prefixed with the packet-type byte
// (0x04 = Message), the binary analog of the leading digit on text frames.
var prefixed = new byte[bin.Length + 1];
prefixed[0] = (byte)EngineIoPacketType.Message;
Buffer.BlockCopy(bin, 0, prefixed, 1, bin.Length);
await _ws.SendAsync(prefixed, WebSocketMessageType.Binary, endOfMessage: true, CancellationToken.None);
}
}
private async Task SendSioAckAsync(int ackId, long arg)

16
SVSim.UnitTests/BattleNode/Integration/RawSocketIoTestClient.cs
View File

@@ -66,7 +66,13 @@ internal sealed class RawSocketIoTestClient : IAsyncDisposable
}
await SendTextAsync($"{(int)EngineIoPacketType.Message}{text}", ct);
foreach (var b in bins)
await _ws.SendAsync(b, WebSocketMessageType.Binary, true, ct);
{
// EIO v3 binary frames are prefixed with the packet-type byte (0x04 = Message).
var prefixed = new byte[b.Length + 1];
prefixed[0] = (byte)EngineIoPacketType.Message;
Buffer.BlockCopy(b, 0, prefixed, 1, b.Length);
await _ws.SendAsync(prefixed, WebSocketMessageType.Binary, true, ct);
}
}
private async Task<string> ReceiveTextAsync(CancellationToken ct)
@@ -92,7 +98,13 @@ internal sealed class RawSocketIoTestClient : IAsyncDisposable
result = await _ws.ReceiveAsync(buffer, ct);
ms.Write(buffer, 0, result.Count);
} while (!result.EndOfMessage);
return ms.ToArray();
var raw = ms.ToArray();
// EIO v3 binary frames are prefixed with the packet-type byte (0x04 = Message). Strip it.
if (raw.Length > 0 && raw[0] == (byte)EngineIoPacketType.Message)
{
return raw.AsSpan(1).ToArray();
}
return raw;
}
private Task SendTextAsync(string text, CancellationToken ct)