/// <summary>
/// Receive web socket result
/// </summary>
/// <param name="buffer">The buffer to copy data into</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <returns>The web socket result details</returns>
public override async Task <WebSocketReceiveResult> ReceiveAsync(ArraySegment <byte> buffer, CancellationToken cancellationToken)
{
try
{
// we may receive control frames so reading needs to happen in an infinite loop
while (true)
{
// allow this operation to be cancelled from iniside OR outside this instance
using (CancellationTokenSource linkedCts = CancellationTokenSource.CreateLinkedTokenSource(_internalReadCts.Token, cancellationToken))
{
WebSocketFrame frame = null;
try
{
frame = await WebSocketFrameReader.ReadAsync(_stream, buffer, linkedCts.Token);
}
catch (InternalBufferOverflowException ex)
{
await CloseOutputAutoTimeoutAsync(WebSocketCloseStatus.MessageTooBig, "Frame too large to fit in buffer. Use message fragmentation", ex);
throw;
}
catch (ArgumentOutOfRangeException ex)
{
await CloseOutputAutoTimeoutAsync(WebSocketCloseStatus.ProtocolError, "Payload length out of range", ex);
throw;
}
catch (EndOfStreamException ex)
{
await CloseOutputAutoTimeoutAsync(WebSocketCloseStatus.InvalidPayloadData, "Unexpected end of stream encountered", ex);
throw;
}
catch (OperationCanceledException ex)
{
await CloseOutputAutoTimeoutAsync(WebSocketCloseStatus.EndpointUnavailable, "Operation cancelled", ex);
throw;
}
catch (Exception ex)
{
await CloseOutputAutoTimeoutAsync(WebSocketCloseStatus.InternalServerError, "Error reading WebSocket frame", ex);
throw;
}
switch (frame.OpCode)
{
case WebSocketOpCode.ConnectionClose:
return(await RespondToCloseFrame(frame, buffer, linkedCts.Token));
case WebSocketOpCode.Ping:
ArraySegment <byte> pingPayload = new ArraySegment <byte>(buffer.Array, buffer.Offset, frame.Count);
await SendPongAsync(pingPayload, linkedCts.Token);
break;
case WebSocketOpCode.Pong:
ArraySegment <byte> pongBuffer = new ArraySegment <byte>(buffer.Array, frame.Count, buffer.Offset);
Pong?.Invoke(this, new PongEventArgs(pongBuffer));
break;
case WebSocketOpCode.TextFrame:
if (!frame.IsFinBitSet)
{
// continuation frames will follow, record the message type Text
_continuationFrameMessageType = WebSocketMessageType.Text;
}
return(new WebSocketReceiveResult(frame.Count, WebSocketMessageType.Text, frame.IsFinBitSet));
case WebSocketOpCode.BinaryFrame:
if (!frame.IsFinBitSet)
{
// continuation frames will follow, record the message type Binary
_continuationFrameMessageType = WebSocketMessageType.Binary;
}
return(new WebSocketReceiveResult(frame.Count, WebSocketMessageType.Binary, frame.IsFinBitSet));
case WebSocketOpCode.ContinuationFrame:
return(new WebSocketReceiveResult(frame.Count, _continuationFrameMessageType, frame.IsFinBitSet));
default:
Exception ex = new NotSupportedException($"Unknown WebSocket opcode {frame.OpCode}");
await CloseOutputAutoTimeoutAsync(WebSocketCloseStatus.ProtocolError, ex.Message, ex);
throw ex;
}
}
}
}
catch (Exception catchAll)
{
// Most exceptions will be caught closer to their source to send an appropriate close message (and set the WebSocketState)
// However, if an unhandled exception is encountered and a close message not sent then send one here
if (_state == WebSocketState.Open)
{
await CloseOutputAutoTimeoutAsync(WebSocketCloseStatus.InternalServerError, "Unexpected error reading from WebSocket", catchAll);
}
throw;
}
}
/// <summary>
/// Read a WebSocket frame from the stream
/// </summary>
/// <param name="fromStream">The stream to read from</param>
/// <param name="intoBuffer">The buffer to read into</param>
/// <param name="cancellationToken">the cancellation token</param>
/// <returns>A websocket frame</returns>
public static async Task <WebSocketReadCursor> ReadAsync(System.IO.Stream fromStream, ArraySegment <byte> intoBuffer,
CancellationToken cancellationToken)
{
// allocate a small buffer to read small chunks of data from the stream
var smallBuffer = new ArraySegment <byte>(new byte[8]);
await BinaryReaderWriter.ReadExactly(2, fromStream, smallBuffer, cancellationToken);
byte byte1 = smallBuffer.Array[0];
byte byte2 = smallBuffer.Array[1];
// process first byte
byte finBitFlag = 0x80;
byte opCodeFlag = 0x0F;
bool isFinBitSet = (byte1 & finBitFlag) == finBitFlag;
WebSocketOpCode opCode = (WebSocketOpCode)(byte1 & opCodeFlag);
// read and process second byte
byte maskFlag = 0x80;
bool isMaskBitSet = (byte2 & maskFlag) == maskFlag;
uint len = await ReadLength(byte2, smallBuffer, fromStream, cancellationToken);
int count = (int)len;
var minCount = CalculateNumBytesToRead(count, intoBuffer.Count);
ArraySegment <byte> maskKey = new ArraySegment <byte>();
try
{
// use the masking key to decode the data if needed
if (isMaskBitSet)
{
maskKey = new ArraySegment <byte>(smallBuffer.Array, 0, WebSocketFrameCommon.MaskKeyLength);
await BinaryReaderWriter.ReadExactly(maskKey.Count, fromStream, maskKey, cancellationToken);
await BinaryReaderWriter.ReadExactly(minCount, fromStream, intoBuffer, cancellationToken);
ArraySegment <byte> payloadToMask =
new ArraySegment <byte>(intoBuffer.Array, intoBuffer.Offset, minCount);
WebSocketFrameCommon.ToggleMask(maskKey, payloadToMask);
}
else
{
await BinaryReaderWriter.ReadExactly(minCount, fromStream, intoBuffer, cancellationToken);
}
}
catch (InternalBufferOverflowException e)
{
throw new InternalBufferOverflowException(
$"Supplied buffer too small to read {0} bytes from {Enum.GetName(typeof(WebSocketOpCode), opCode)} frame",
e);
}
WebSocketFrame frame;
if (opCode == WebSocketOpCode.ConnectionClose)
{
frame = DecodeCloseFrame(isFinBitSet, opCode, count, intoBuffer, maskKey);
}
else
{
// note that by this point the payload will be populated
frame = new WebSocketFrame(isFinBitSet, opCode, count, maskKey);
}
return(new WebSocketReadCursor(frame, minCount, count - minCount));
}