private async Task <WebSocketCloseResult> ReceiveLoop(Func <WebSocketFrame, object, Task> messageHandler, object state, CancellationToken cancellationToken)
{
while (!cancellationToken.IsCancellationRequested)
{
// WebSocket Frame layout (https://tools.ietf.org/html/rfc6455#section-5.2):
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-------+-+-------------+-------------------------------+
// |F|R|R|R| opcode|M| Payload len | Extended payload length |
// |I|S|S|S| (4) |A| (7) | (16/64) |
// |N|V|V|V| |S| | (if payload len==126/127) |
// | |1|2|3| |K| | |
// +-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
// | Extended payload length continued, if payload len == 127 |
// + - - - - - - - - - - - - - - - +-------------------------------+
// | |Masking-key, if MASK set to 1 |
// +-------------------------------+-------------------------------+
// | Masking-key (continued) | Payload Data |
// +-------------------------------- - - - - - - - - - - - - - - - +
// : Payload Data continued ... :
// + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
// | Payload Data continued ... |
// +---------------------------------------------------------------+
// Read at least 2 bytes
var result = await _inbound.ReadAtLeastAsync(2, cancellationToken);
cancellationToken.ThrowIfCancellationRequested();
if (result.IsCompleted && result.Buffer.Length < 2)
{
return(WebSocketCloseResult.AbnormalClosure);
}
var buffer = result.Buffer;
// Read the opcode
var opcodeByte = buffer.ReadBigEndian <byte>();
buffer = buffer.Slice(1);
var fin = (opcodeByte & 0x80) != 0;
var opcodeNum = opcodeByte & 0x0F;
var opcode = (WebSocketOpcode)opcodeNum;
if ((opcodeByte & 0x70) != 0)
{
// Reserved bits set, this frame is invalid, close our side and terminate immediately
return(await CloseFromProtocolError(cancellationToken, 0, default(ReadableBuffer), "Reserved bits, which are required to be zero, were set."));
}
else if ((opcodeNum >= 0x03 && opcodeNum <= 0x07) || (opcodeNum >= 0x0B && opcodeNum <= 0x0F))
{
// Reserved opcode
return(await CloseFromProtocolError(cancellationToken, 0, default(ReadableBuffer), $"Received frame using reserved opcode: 0x{opcodeNum:X}"));
}
// Read the first byte of the payload length
var lenByte = buffer.ReadBigEndian <byte>();
buffer = buffer.Slice(1);
var masked = (lenByte & 0x80) != 0;
var payloadLen = (lenByte & 0x7F);
// Mark what we've got so far as consumed
_inbound.Advance(buffer.Start);
// Calculate the rest of the header length
var headerLength = masked ? 4 : 0;
if (payloadLen == 126)
{
headerLength += 2;
}
else if (payloadLen == 127)
{
headerLength += 8;
}
uint maskingKey = 0;
if (headerLength > 0)
{
result = await _inbound.ReadAtLeastAsync(headerLength, cancellationToken);
cancellationToken.ThrowIfCancellationRequested();
if (result.IsCompleted && result.Buffer.Length < headerLength)
{
return(WebSocketCloseResult.AbnormalClosure);
}
buffer = result.Buffer;
// Read extended payload length (if any)
if (payloadLen == 126)
{
payloadLen = buffer.ReadBigEndian <ushort>();
buffer = buffer.Slice(sizeof(ushort));
}
else if (payloadLen == 127)
{
var longLen = buffer.ReadBigEndian <ulong>();
buffer = buffer.Slice(sizeof(ulong));
if (longLen > int.MaxValue)
{
throw new WebSocketException($"Frame is too large. Maximum frame size is {int.MaxValue} bytes");
}
payloadLen = (int)longLen;
}
// Read masking key
if (masked)
{
var maskingKeyStart = buffer.Start;
maskingKey = buffer.Slice(0, 4).ReadBigEndian <uint>();
buffer = buffer.Slice(4);
}
// Mark the length and masking key consumed
_inbound.Advance(buffer.Start);
}
var payload = default(ReadableBuffer);
if (payloadLen > 0)
{
result = await _inbound.ReadAtLeastAsync(payloadLen, cancellationToken);
cancellationToken.ThrowIfCancellationRequested();
if (result.IsCompleted && result.Buffer.Length < payloadLen)
{
return(WebSocketCloseResult.AbnormalClosure);
}
buffer = result.Buffer;
payload = buffer.Slice(0, payloadLen);
if (masked)
{
// Unmask
MaskingUtilities.ApplyMask(ref payload, maskingKey);
}
}
// Run the callback, if we're not cancelled.
cancellationToken.ThrowIfCancellationRequested();
var frame = new WebSocketFrame(fin, opcode, payload);
if (frame.Opcode.IsControl() && !frame.EndOfMessage)
{
// Control frames cannot be fragmented.
return(await CloseFromProtocolError(cancellationToken, payloadLen, payload, "Control frames may not be fragmented"));
}
else if (_currentMessageType != WebSocketOpcode.Continuation && opcode.IsMessage() && opcode != 0)
{
return(await CloseFromProtocolError(cancellationToken, payloadLen, payload, "Received non-continuation frame during a fragmented message"));
}
else if (_currentMessageType == WebSocketOpcode.Continuation && frame.Opcode == WebSocketOpcode.Continuation)
{
return(await CloseFromProtocolError(cancellationToken, payloadLen, payload, "Continuation Frame was received when expecting a new message"));
}
if (frame.Opcode == WebSocketOpcode.Close)
{
// Allowed frame lengths:
// 0 - No body
// 2 - Code with no reason phrase
// >2 - Code and reason phrase (must be valid UTF-8)
if (frame.Payload.Length > 125)
{
return(await CloseFromProtocolError(cancellationToken, payloadLen, payload, "Close frame payload too long. Maximum size is 125 bytes"));
}
else if ((frame.Payload.Length == 1) || (frame.Payload.Length > 2 && !Utf8Validator.ValidateUtf8(payload.Slice(2))))
{
return(await CloseFromProtocolError(cancellationToken, payloadLen, payload, "Close frame payload invalid"));
}
ushort?actualStatusCode;
var closeResult = HandleCloseFrame(payload, frame, out actualStatusCode);
// Verify the close result
if (actualStatusCode != null)
{
var statusCode = actualStatusCode.Value;
if (statusCode < 1000 || statusCode == 1004 || statusCode == 1005 || statusCode == 1006 || (statusCode > 1011 && statusCode < 3000))
{
return(await CloseFromProtocolError(cancellationToken, payloadLen, payload, $"Invalid close status: {statusCode}."));
}
}
// Make the payload as consumed
if (payloadLen > 0)
{
_inbound.Advance(payload.End);
}
return(closeResult);
}
else
{
if (frame.Opcode == WebSocketOpcode.Ping)
{
// Check the ping payload length
if (frame.Payload.Length > 125)
{
// Payload too long
return(await CloseFromProtocolError(cancellationToken, payloadLen, payload, "Ping frame exceeded maximum size of 125 bytes"));
}
await SendCoreAsync(
frame.EndOfMessage,
WebSocketOpcode.Pong,
payloadAllocLength : 0,
payloadLength : payload.Length,
payloadWriter : AppendPayloadWriter,
payload : payload,
cancellationToken : cancellationToken);
}
var effectiveOpcode = opcode == WebSocketOpcode.Continuation ? _currentMessageType : opcode;
if (effectiveOpcode == WebSocketOpcode.Text && !_validator.ValidateUtf8Frame(frame.Payload, frame.EndOfMessage))
{
// Drop the frame and immediately close with InvalidPayload
return(await CloseFromProtocolError(cancellationToken, payloadLen, payload, "An invalid Text frame payload was received", statusCode : WebSocketCloseStatus.InvalidPayloadData));
}
else if (_options.PassAllFramesThrough || (frame.Opcode != WebSocketOpcode.Ping && frame.Opcode != WebSocketOpcode.Pong))
{
await messageHandler(frame, state);
}
}
if (fin)
{
// Reset the UTF8 validator
_validator.Reset();
// If it's a non-control frame, reset the message type tracker
if (opcode.IsMessage())
{
_currentMessageType = WebSocketOpcode.Continuation;
}
}
// If there isn't a current message type, and this was a fragmented message frame, set the current message type
else if (!fin && _currentMessageType == WebSocketOpcode.Continuation && opcode.IsMessage())
{
_currentMessageType = opcode;
}
// Mark the payload as consumed
if (payloadLen > 0)
{
_inbound.Advance(payload.End);
}
}
return(WebSocketCloseResult.AbnormalClosure);
}
/// <summary> /// Sends the specified frame. /// </summary> /// <param name="message">The message to send.</param> /// <returns>A <see cref="Task"/> that completes when the message has been written to the outbound stream.</returns> public static Task SendAsync(this IWebSocketConnection self, WebSocketFrame message) => self.SendAsync(message, CancellationToken.None);