protected override async Task ProtectedWriteAsync(
byte[] buffer,
int offset,
int count,
CancellationToken cancellationToken)
{
if (count > this.MaxWriteSize)
{
throw new IndexOutOfRangeException(
$"Write buffer too large ({count}), must be at most {this.MaxWriteSize}");
}
while (true)
{
try
{
var connection = await ConnectAsync(cancellationToken).ConfigureAwait(false);
// Take care of outstanding ACKs.
var bytesToAck = Thread.VolatileRead(ref this.bytesReceived);
if (this.lastAck < bytesToAck)
{
var ackMessage = new MessageBuffer(
new byte[AckMessage.ExpectedLength]).AsAckMessage();
ackMessage.Tag = MessageTag.ACK;
ackMessage.Ack = bytesToAck;
TraceLine($"Sending ACK #{ackMessage.Ack}...");
await connection.WriteAsync(
ackMessage.Buffer,
0,
(int)AckMessage.ExpectedLength,
cancellationToken).ConfigureAwait(false);
this.lastAck = ackMessage.Ack;
}
// Send data.
var newMessage = new DataMessage((uint)count);
newMessage.Tag = MessageTag.DATA;
newMessage.DataLength = (uint)count;
newMessage.SequenceNumber = Thread.VolatileRead(ref this.bytesSent);
Array.Copy(buffer, offset, newMessage.Buffer, DataMessage.DataOffset, count);
TraceLine($"Sending DATA #{newMessage.SequenceNumber}...");
// Update bytesSent before we write the data to the wire,
// otherwise we might see an ACK before bytesSent even reflects
// that the data has been sent.
this.bytesSent = Thread.VolatileRead(ref this.bytesSent) + (ulong)count;
await connection.WriteAsync(
newMessage.Buffer,
0,
newMessage.BufferLength,
cancellationToken).ConfigureAwait(false);
// We should get an ACK for this message.
this.sentButUnacknoledgedQueue.Enqueue(newMessage);
return;
}
catch (WebSocketStreamClosedByServerException e)
{
if (e.CloseStatus == WebSocketCloseStatus.NormalClosure ||
(CloseCode)e.CloseStatus == CloseCode.DESTINATION_READ_FAILED ||
(CloseCode)e.CloseStatus == CloseCode.DESTINATION_WRITE_FAILED)
{
// The server closed the connection and us sending more data
// really seems unexpected.
throw;
}
else if ((CloseCode)e.CloseStatus == CloseCode.NOT_AUTHORIZED)
{
TraceLine("NOT_AUTHORIZED");
throw new UnauthorizedException(e.CloseStatusDescription);
}
else
{
TraceLine($"Connection closed abnormally: {(CloseCode)e.CloseStatus}");
TraceLine("Disconnecting, preparing to reconnect");
await DisconnectAsync(cancellationToken).ConfigureAwait(false);
}
}
}
}
protected override async Task <int> ProtectedReadAsync(
byte[] buffer,
int offset,
int count,
CancellationToken cancellationToken)
{
if (count < this.MinReadSize)
{
throw new IndexOutOfRangeException(
$"Read buffer too small ({count}), must be at least {this.MinReadSize}");
}
MessageBuffer receiveBuffer = new MessageBuffer(new byte[count + DataMessage.DataOffset]);
while (true)
{
try
{
var connection = await ConnectAsync(cancellationToken).ConfigureAwait(false);
int bytesRead = await connection.ReadAsync(
receiveBuffer.Buffer,
0,
receiveBuffer.Buffer.Length,
cancellationToken).ConfigureAwait(false);
if (bytesRead == 0)
{
TraceLine("Server closed connection");
// We are done here
return(0);
}
else if (bytesRead < 2)
{
throw new InvalidServerResponseException("Truncated message received");
}
var tag = receiveBuffer.PeekMessageTag();
switch (tag)
{
case MessageTag.CONNECT_SUCCESS_SID:
{
this.Sid = receiveBuffer.AsSidMessage().Sid;
TraceLine($"Connected session <{this.Sid}>");
// No data to return to client yet.
break;
}
case MessageTag.RECONNECT_SUCCESS_ACK:
{
var reconnectMessage = receiveBuffer.AsAckMessage();
var lastAckReceived = Thread.VolatileRead(ref this.bytesSentAndAcknoledged);
if (lastAckReceived < reconnectMessage.Ack)
{
TraceLine("Last ACK sent by server was not received");
bytesSentAndAcknoledged = reconnectMessage.Ack;
}
else if (lastAckReceived > reconnectMessage.Ack)
{
Debug.Assert(false, "Server acked backwards");
throw new Exception("Server acked backwards");
}
else
{
TraceLine($"Reconnected session <{this.Sid}>");
}
// No data to return to client yet.
break;
}
case MessageTag.ACK:
{
var ackMessage = receiveBuffer.AsAckMessage();
if (ackMessage.Ack <= 0 || ackMessage.Ack > Thread.VolatileRead(ref this.bytesSent))
{
throw new InvalidServerResponseException("Received invalid ACK");
}
this.bytesSentAndAcknoledged = ackMessage.Ack;
// The server might be acknolodging multiple messages at once.
while (this.sentButUnacknoledgedQueue.Count > 0 &&
this.sentButUnacknoledgedQueue.Peek().ExpectedAck
<= Thread.VolatileRead(ref this.bytesSentAndAcknoledged))
{
this.sentButUnacknoledgedQueue.Dequeue();
}
TraceLine($"Received ACK #{ackMessage.Ack}");
// No data to return to client yet.
break;
}
case MessageTag.DATA:
{
var dataMessage = receiveBuffer.AsDataMessage();
TraceLine($"Received data ({dataMessage.DataLength} bytes)");
bytesReceived += dataMessage.DataLength;
// Copy data to caller's buffer.
Debug.Assert(dataMessage.DataLength < count);
Array.Copy(
receiveBuffer.Buffer,
DataMessage.DataOffset,
buffer,
offset,
dataMessage.DataLength);
return((int)dataMessage.DataLength);
}
default:
if (this.Sid == null)
{
// An unrecognized tag at the start of a connection means that we are
// essentially reading junk, so bail out.
throw new InvalidServerResponseException($"Unknown tag: {tag}");
}
else
{
// The connection was properly opened - an unrecognized tag merely
// means that the server uses a feature that we do not support (yet).
// In accordance with the protocol specification, ignore this tag.
break;
}
}
}
catch (WebSocketStreamClosedByClientException)
{
TraceLine("Detected attempt to read after close");
throw;
}
catch (WebSocketStreamClosedByServerException e)
{
if (e.CloseStatus == WebSocketCloseStatus.NormalClosure ||
(CloseCode)e.CloseStatus == CloseCode.DESTINATION_READ_FAILED ||
(CloseCode)e.CloseStatus == CloseCode.DESTINATION_WRITE_FAILED)
{
TraceLine("Server closed connection");
// Server closed the connection normally, we are done here
return(0);
}
else if ((CloseCode)e.CloseStatus == CloseCode.NOT_AUTHORIZED)
{
TraceLine("Not authorized");
throw new UnauthorizedException(e.CloseStatusDescription);
}
else if ((CloseCode)e.CloseStatus == CloseCode.SID_UNKNOWN ||
(CloseCode)e.CloseStatus == CloseCode.SID_IN_USE)
{
// Failed reconect attempt - do not try again.
TraceLine("Sid unknown or in use");
throw new WebSocketStreamClosedByServerException(
e.CloseStatus,
"Connection losed abnormally and an attempt to reconnect was rejected");
}
else if ((CloseCode)e.CloseStatus == CloseCode.FAILED_TO_CONNECT_TO_BACKEND)
{
// Server probably not listening.
TraceLine("Failed to connect to backend");
throw new WebSocketStreamClosedByServerException(
e.CloseStatus,
"Failed to connect to backend");
}
else
{
TraceLine($"Connection closed abnormally: {(CloseCode)e.CloseStatus}");
TraceLine("Disconnecting, preparing to reconnect");
await DisconnectAsync(cancellationToken).ConfigureAwait(false);
}
}
}
}