private async void StartSending(UInt64 subscriberId, SubscriberRecord subscriber)
{
try {
var lastRevisions = new Dictionary <UInt32, UInt32>(); // {topic} => {revision}
// Loop until disposed or closed
while (!IsDisposed && subscriber.Socket.State == WebSocketState.Open)
{
foreach (var topicRecord in TopicRecords)
{
// If the client is in need of an update
if (subscriber.Channels.Contains(topicRecord.Value.Channel) && // Correct channel
(!lastRevisions.TryGetValue(topicRecord.Key, out var lastRevision) || lastRevision < topicRecord.Value.Revision)) // There's a new revision
{
// Send update
await subscriber.Socket.SendAsync(topicRecord.Value.Packet, WebSocketMessageType.Binary, true, CancellationToken.None);
// Note latest revision sent
lastRevisions[topicRecord.Key] = topicRecord.Value.Revision;
}
}
// Wait for next change
subscriber.SendLock.WaitOne();
}
} catch (ObjectDisposedException) {
} catch (Exception e) {
Trace.TraceWarning($"Subscriber {subscriberId} TX: {e.Message}");
}
}
private async void StartReceiving(UInt64 subscriberId, SubscriberRecord subscriber)
{
var receiveBuffer = new Byte[512]; // TODO
try {
while (!IsDisposed && subscriber.Socket.State == WebSocketState.Open)
{
// Receive message into buffer
var receiveResult = await subscriber.Socket.ReceiveAsync(new ArraySegment <Byte>(receiveBuffer), CancellationToken.None);
// Close connection if requested
if (receiveResult.MessageType == WebSocketMessageType.Close)
{
await subscriber.Socket.CloseAsync(WebSocketCloseStatus.NormalClosure, "", CancellationToken.None);
continue;
}
// Close connection on bad message type
if (receiveResult.MessageType == WebSocketMessageType.Text)
{
await subscriber.Socket.CloseAsync(WebSocketCloseStatus.InvalidMessageType, "Cannot accept text frame", CancellationToken.None);
continue;
}
// Close connection if message too long
if (!receiveResult.EndOfMessage)
{
await subscriber.Socket.CloseAsync(WebSocketCloseStatus.MessageTooBig, "Message too big", CancellationToken.None);
continue;
}
//await subscriber.Socket.SendAsync(new ArraySegment<Byte>(receiveBuffer, 0, receiveResult.Count), WebSocketMessageType.Binary, receiveResult.EndOfMessage, CancellationToken.None);
}
} catch (ObjectDisposedException) { // TODO: other exceptions
} catch (Exception e) {
Trace.TraceWarning($"Subscriber {subscriberId} RX: {e.Message}");
} finally {
subscriber.Socket.Dispose();
SubscriberRecords.TryRemove(subscriberId, out subscriber);
}
}
private void ReceieveThread_OnSpin(Object obj)
{
var buffer = new Byte[Mtu];
try {
while (!IsDisposed)
{
try {
// Remove all expired subscriptions TODO - should be on a timer?
var expiry = DateTime.UtcNow.Subtract(KeepAliveInterval).Subtract(KeepAiveGrace);
foreach (var ep in SubscriberRecords.Where(a => a.Value.LastAuthorizedAt < expiry).Select(a => a.Key))
{
SubscriberRecords.TryRemove(ep, out var record);
Trace.WriteLine($"{ep} Subscription expired.", "server-receive");
}
// Wait for packet to arrive
var endpoint = (EndPoint) new IPEndPoint(IPAddress.Any, 0);
var len = Socket.ReceiveFrom(buffer, ref endpoint);
if (len < 1)
{
Trace.WriteLine($"Strange byte count {len}.", "server-receive-warning");
continue;
}
// Check packet sanity
if (len < Constants.CLIENTTXHEADER_LENGTH)
{
Trace.WriteLine($"{endpoint} Received packet that is too small to be valid. Discarded.", "server-receive");
continue;
}
if ((len - Constants.CLIENTTXHEADER_LENGTH) % 6 > 0)
{
Trace.WriteLine($"{endpoint} Received packet is not a valid length. Discarded.", "server-receive");
continue;
}
// Check version
var version = buffer[0];
if (version != Constants.VERSION)
{
Trace.WriteLine($"{endpoint} Received packet version does not match or is corrupted. Discarded.", "server-receive");
continue;
}
// Check authorization token
var authorizationToken = new Byte[16];
Buffer.BlockCopy(buffer, 1, authorizationToken, 0, authorizationToken.Length);
if (!AuthorizationFilter(endpoint, authorizationToken))
{
Trace.WriteLine($"{endpoint} Received packet with rejected authorization token. Discarded.", "server-receive");
continue;
}
// Find subscriber record
if (SubscriberRecords.TryGetValue(endpoint, out var subscriberRecord))
{
// Record exists, update authorizedAt
subscriberRecord.LastAuthorizedAt = DateTime.UtcNow;
// Process ACKs
var pos = Constants.CLIENTTXHEADER_LENGTH;
if (pos == len)
{
Trace.WriteLine($"{endpoint} Sent keep-alive.", "server-receive");
}
while (pos < len)
{
// Extract topic
var topic = BitConverter.ToUInt32(buffer, pos);
// Extract revision
var revision = BitConverter.ToUInt16(buffer, pos + 4);
Trace.WriteLine($"{endpoint} Acknowledged {topic}#{revision}.", "server-receive");
if (TopicRecords.TryGetValue(topic, out var topicRecord))
{
if (topicRecord.Revision == revision)
{
topicRecord.PendingSubscribers = topicRecord.PendingSubscribers.Except(new EndPoint[] { endpoint }).ToArray(); // Replace rather than adding so we don't have a sync issue
}
}
pos += 10;
}
}
else
{
// Record doesn't exist, created
subscriberRecord = SubscriberRecords[endpoint] = new SubscriberRecord()
{
LastAuthorizedAt = DateTime.UtcNow,
};
// Queue sending latest value from all topics
foreach (var topicRecord in TopicRecords.Select(a => a.Value))
{
topicRecord.PendingSubscribers = topicRecord.PendingSubscribers.Union(new EndPoint[] { endpoint }).ToArray(); // Replace rather than adding so we don't have a sync issue
}
}
} catch (SocketException ex) {
if (ex.SocketErrorCode == SocketError.TimedOut)
{
continue;
}
Trace.WriteLine($"Socket error {ex.SocketErrorCode}.", "server-receive-warning");
}
}
} catch (ObjectDisposedException) { }
}
private async void AcceptThread_OnSpin(Object obj)
{
try {
// Loop until disposed
while (!IsDisposed)
{
// Wait for inbound request
var listenerContext = await Listener.GetContextAsync();
// Respond to options requests
if (listenerContext.Request.HttpMethod == "OPTIONS")
{
listenerContext.Response.AddHeader("Access-Control-Allow-Headers", "Content-Type, Accept, X-Requested-With");
listenerContext.Response.AddHeader("Access-Control-Allow-Methods", "GET");
listenerContext.Response.AddHeader("Access-Control-Max-Age", "86400");
listenerContext.Response.Close();
continue;
}
listenerContext.Response.AppendHeader("Access-Control-Allow-Origin", "*");
// Handle requests for client
if (listenerContext.Request.Url.PathAndQuery == "/client.ts")
{
listenerContext.Response.StatusCode = 200;
listenerContext.Response.StatusDescription = "OK";
listenerContext.Response.ContentType = "application/typescript";
listenerContext.Response.Close(ClientTypeScript, false);
continue;
}
if (listenerContext.Request.Url.PathAndQuery == "/client.js")
{
listenerContext.Response.StatusCode = 200;
listenerContext.Response.StatusDescription = "OK";
listenerContext.Response.ContentType = "application/javascript";
listenerContext.Response.Close(ClientJavaScript, false);
continue;
}
// Favicon
if (listenerContext.Request.Url.PathAndQuery == "/favicon.ico")
{
listenerContext.Response.StatusCode = 404;
listenerContext.Response.StatusDescription = "Not found";
listenerContext.Response.Close(ClientJavaScript, false);
continue;
}
// Reject if not a websocket request
if (!listenerContext.Request.IsWebSocketRequest)
{
listenerContext.Response.StatusCode = 426;
listenerContext.Response.StatusDescription = "WebSocket required";
listenerContext.Response.Close();
continue;
}
// Get channel list
var channelsStrings = listenerContext.Request.QueryString["channels"];
if (String.IsNullOrWhiteSpace(channelsStrings))
{
listenerContext.Response.StatusCode = 400;
listenerContext.Response.StatusDescription = "Missing channels";
listenerContext.Response.Close();
continue;
}
var channels = new List <UInt32>();
foreach (var channelString in channelsStrings.Split(','))
{
if (!UInt32.TryParse(channelString, out var channel))
{
listenerContext.Response.StatusCode = 400;
listenerContext.Response.StatusDescription = $"Bad channel {channelString}";
listenerContext.Response.Close();
continue;
}
channels.Add(channel);
}
// TODO: reject if not secure?
// TODO: authentication
// Upgrade to web sockets
WebSocketContext webSocketContext = null;
try {
webSocketContext = await listenerContext.AcceptWebSocketAsync(SubProtocol, KeepAliveInterval);
} catch (Exception e) {
listenerContext.Response.StatusCode = 400;
listenerContext.Response.StatusDescription = e.Message; // TODO: bad idea?
listenerContext.Response.Close();
return;
}
// Create subscriber record
var subscriberId = (UInt64)(Interlocked.Increment(ref NextSubscriberId) - Int64.MinValue);
var subscriber = SubscriberRecords[subscriberId] = new SubscriberRecord()
{
Socket = webSocketContext.WebSocket,
Channels = channels.ToArray()
};
Task.Run(async() => StartReceiving(subscriberId, subscriber)); // TODO: Clean this up
Task.Run(async() => StartSending(subscriberId, subscriber));
}
} catch (ObjectDisposedException) { }
}