Develop Reference

ClientWebSocket example hangs

The example shown on the following page doesn't work:
Using c# ClientWebSocket with streams
It hangs on the following line:
await ws.ConnectAsync(serverUri, CancellationToken.None);
It appears the connection is not made.
Please indicate the simplest modification to make the following code work. I do not wish to use any 3rd party tools or libraries.
private static async Task DoClientWebSocket()
{
using (ClientWebSocket ws = new ClientWebSocket())
{
Uri serverUri = new Uri("wss://echo.websocket.org/");
await ws.ConnectAsync(serverUri, CancellationToken.None);
while (ws.State == WebSocketState.Open)
{
string msg = "hello123";
ArraySegment<byte> bytesToSend = new ArraySegment<byte>(Encoding.UTF8.GetBytes(msg));
await ws.SendAsync(bytesToSend, WebSocketMessageType.Text, true, CancellationToken.None);
ArraySegment<byte> bytesReceived = new ArraySegment<byte>(new byte[1024]);
WebSocketReceiveResult result = await ws.ReceiveAsync(bytesReceived, CancellationToken.None);
Console.WriteLine(Encoding.UTF8.GetString(bytesReceived.Array, 0, result.Count));
}
}
}

You are correct. You don't need to add any header in order to use wss://echo.websocket.org/. Your code run just fine at my end. But I'll suggest one improvement to include timeout for your ConnectAsync, SendAsync and ReceiveAsync calls so that it do not get stuck for long.
I have restricted code to call SendAsync to just 5 times so that its easier to verify output.
[Edited:] Include logic to receive complete response by calling `ReceiveAsync multiple times.
private static async Task DoClientWebSocket()
{
using (ClientWebSocket ws = new ClientWebSocket())
{
Uri serverUri = new Uri("wss://echo.websocket.org/");
//Implementation of timeout of 5000 ms
var source = new CancellationTokenSource();
source.CancelAfter(5000);
await ws.ConnectAsync(serverUri, source.Token);
var iterationNo = 0;
// restricted to 5 iteration only
while (ws.State == WebSocketState.Open && iterationNo++ < 5)
{
string msg = "hello0123456789123456789123456789123456789123456789123456789";
ArraySegment<byte> bytesToSend =
new ArraySegment<byte>(Encoding.UTF8.GetBytes(msg));
await ws.SendAsync(bytesToSend, WebSocketMessageType.Text,
true, source.Token);
//Receive buffer
var receiveBuffer = new byte[200];
//Multipacket response
var offset = 0;
var dataPerPacket = 10; //Just for example
while (true)
{
ArraySegment<byte> bytesReceived =
new ArraySegment<byte>(receiveBuffer, offset, dataPerPacket);
WebSocketReceiveResult result = await ws.ReceiveAsync(bytesReceived,
source.Token);
//Partial data received
Console.WriteLine("Data:{0}",
Encoding.UTF8.GetString(receiveBuffer, offset,
result.Count));
offset += result.Count;
if (result.EndOfMessage)
break;
}
Console.WriteLine("Complete response: {0}",
Encoding.UTF8.GetString(receiveBuffer, 0,
offset));
}
}
}
static void Main(string[] args)
{
var taskWebConnect = Task.Run(() => DoClientWebSocket());
taskWebConnect.Wait();
}
Output on command prompt:
Data:hello01234
Data:5678912345
Data:6789123456
Data:7891234567
Data:8912345678
Data:9123456789
Complete response: hello0123456789123456789123456789123456789123456789123456789

Couldn't fetch response more than 4096 byte in Chat (Socket) [duplicate]

I am receiving JSON through a websocket. At least: I am partially. Using an online websocket service I receive the full JSON response (all the HTML markup is ignored). When I look at the JSON that I receive in my console I can see the HTML markup (viewing it with the HTML viewer during debugging removes the HTML) but it ends abruptly (incomplete data).
My buffer has plenty of space and I am using async-await to (supposedly) wait for the entire response to come in before continuing.
private async Task Receive()
{
var buffer = new byte[4096 * 20];
while (_socket.State == WebSocketState.Open)
{
var response = await _socket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);
if (response.MessageType == WebSocketMessageType.Close)
{
await
_socket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Close response received",
CancellationToken.None);
}
else
{
var result = Encoding.UTF8.GetString(buffer);
var a = buffer[1000];
var b = buffer[10000];
var c = buffer[50000];
var d = buffer[81000];
Console.WriteLine(result);
var responseObject = JsonConvert.DeserializeObject<Response>(result, _requestParameters.ResponseDataType);
OnSocketReceive.Invoke(this, new SocketEventArgs {Response = responseObject });
buffer = new byte[4096 * 20];
}
}
}
Things to note: The buffer is perfectly big enough and b, c and d are never filled. I should also note that this only happens for the 1-questions-newest-tag-java request, 155-questions-active works perfectly fine.
After doing some digging I have found that response.CloseStatus and response.CloseStatusDescription are always null, response.Count is always 1396 (copy-pasting the result in Word does show that there are always 1396 characters) and response.EndOfMessage is false.
Digging through some source code I have found that the DefaultReceiveBufferSize is 16 * 1024 (big enough) and the WebSocketGetDefaultKeepAliveInterval() refers to an external implementation (but the debugger shows 00:00:30).
It is not a matter of timeout since the debugger halts at the same moment the online service receives its response.
Why is my method continuing to execute when the socket has not yet received all data?

Just to complete #Noseratio response, the code would be something like this:
ArraySegment<Byte> buffer = new ArraySegment<byte>(new Byte[8192]);
WebSocketReceiveResult result= null;
using (var ms = new MemoryStream())
{
do
{
result = await socket.ReceiveAsync(buffer, CancellationToken.None);
ms.Write(buffer.Array, buffer.Offset, result.Count);
}
while (!result.EndOfMessage);
ms.Seek(0, SeekOrigin.Begin);
if (result.MessageType == WebSocketMessageType.Text)
{
using (var reader = new StreamReader(ms, Encoding.UTF8))
{
// do stuff
}
}
}
Cheers.

I might be wrong, but I don't think you're always supposed to receive a complete WebSocket message at once. The server may be sending the message in chunks (that'd correspond to calling SendAsync with endOfMessage: false).
So, do await _socket.ReceiveAsync() in a loop and accumulate the received chunks, until WebSocketReceiveResult.EndOfMessage is true or an error has occured.
On a side note, you probably should be using WebSocket.CreateClientBuffer instead of new ArraySegment<byte>(buffer).

// Read the bytes from the web socket and accumulate all into a list.
var buffer = new ArraySegment<byte>(new byte[1024]);
WebSocketReceiveResult result = null;
var allBytes = new List<byte>();
do
{
result = await webSocket.ReceiveAsync(buffer, CancellationToken.None);
for (int i = 0; i < result.Count; i++)
{
allBytes.Add(buffer.Array[i]);
}
}
while (!result.EndOfMessage);
// Optional step to convert to a string (UTF-8 encoding).
var text = Encoding.UTF8.GetString(allBytes.ToArray(), 0, allBytes.Count);

Following Noseratio's answer I have implemented a temporary buffer that will construct the data of the entire message.
var temporaryBuffer = new byte[BufferSize];
var buffer = new byte[BufferSize * 20];
int offset = 0;
WebSocketReceiveResult response;
while (true)
{
response = await _socket.ReceiveAsync(
new ArraySegment<byte>(temporaryBuffer),
CancellationToken.None);
temporaryBuffer.CopyTo(buffer, offset);
offset += response.Count;
temporaryBuffer = new byte[BufferSize];
if (response.EndOfMessage)
{
break;
}
}
Full implementation here

Try this:
try
{
WebSocketReceiveResult result;
string receivedMessage = "";
var message = new ArraySegment<byte>(new byte[4096]);
do
{
result = await WebSocket.ReceiveAsync(message, DisconectToken);
if (result.MessageType != WebSocketMessageType.Text)
break;
var messageBytes = message.Skip(message.Offset).Take(result.Count).ToArray();
receivedMessage += Encoding.UTF8.GetString(messageBytes);
}
while (!result.EndOfMessage);
if (receivedMessage != "{}" && !string.IsNullOrEmpty(receivedMessage))
{
ResolveWebSocketResponse.Invoke(receivedMessage, Connection);
Console.WriteLine("Received: {0}", receivedMessage);
}
}
catch (Exception ex)
{
var mes = ex.Message;
}

Get data from GDAX web socket feed

I want to get data from this wss://ws-feed.gdax.com
I don't know anything about websocket. I am reading some tutorials and it uses terms like websocket server, TCP, etc which I have no idea about. Can anyone please advice how should I proceed, how to write a c# code to get data from the above.
This is the document which I reading to fetch real time data - https://docs.gdax.com/#websocket-feed
Started by creating a window app. Read here that the WebSocketSharp library can be used to connect WebSockets so installed it and so far written this code:
using (var ws = new WebSocket("wss://ws-feed.gdax.com"))
{
ws.Connect();
string json = "{\"type\": \"subscribe\", \"product_ids\": [\"BTC-USD\"]}";
ws.Send(json); //gives error -Function evaluation disabled because a previous function evaluation timed out. You must continue execution to reenable function evaluation.
}
Any help would be much appreciated.

ClientWebSocket socket = new ClientWebSocket();
Task task = socket.ConnectAsync(new Uri("wss://ws-feed.gdax.com"), CancellationToken.None);
task.Wait();
Thread readThread = new Thread(
delegate(object obj)
{
byte[] recBytes = new byte[1024];
while (true) {
ArraySegment<byte> t = new ArraySegment<byte>(recBytes);
Task<WebSocketReceiveResult> receiveAsync = socket.ReceiveAsync(t, CancellationToken.None);
receiveAsync.Wait();
string jsonString = Encoding.UTF8.GetString(recBytes);
Console.Out.WriteLine("jsonString = {0}", jsonString);
recBytes = new byte[1024];
}
});
readThread.Start();
string json = "{\"product_ids\":[\"btc-usd\"],\"type\":\"subscribe\"}";
byte[] bytes = Encoding.UTF8.GetBytes(json);
ArraySegment<byte> subscriptionMessageBuffer = new ArraySegment<byte>(bytes);
socket.SendAsync(subscriptionMessageBuffer, WebSocketMessageType.Text, true, CancellationToken.None);
Console.ReadLine();

Basically, what you do is in the right direction. Just check websocket state before you read the message.
The below example is from https://github.com/sefbkn/gdax.netcore, with little modification
var webSocketClient = new ClientWebSocket();
var cancellationToken = new CancellationToken();
await webSocketClient.ConnectAsync(new Uri("wss://ws-feed.gdax.com"), cancellationToken).ConfigureAwait(false);
if (webSocketClient.State == WebSocketState.Open)
{
var requestString = JsonConvert.SerializeObject(new {
type = "subscribe",
product_ids = new[]{"ETH-EUR"},
channels = new[]{"ticker"}
});
var requestBytes = UTF8Encoding.UTF8.GetBytes(requestString);
var subscribeRequest = new ArraySegment<byte>(requestBytes);
var sendCancellationToken = new CancellationToken();
await webSocketClient.SendAsync(subscribeRequest, WebSocketMessageType.Text, true, sendCancellationToken).ConfigureAwait(false);
while (webSocketClient.State == WebSocketState.Open)
{
var receiveCancellationToken = new CancellationToken();
using(var stream = new MemoryStream(1024))
{
var receiveBuffer = new ArraySegment<byte>(new byte[1024*8]);
WebSocketReceiveResult webSocketReceiveResult;
do
{
webSocketReceiveResult = await webSocketClient.ReceiveAsync(receiveBuffer, receiveCancellationToken).ConfigureAwait(false);
await stream.WriteAsync(receiveBuffer.Array, receiveBuffer.Offset, receiveBuffer.Count);
} while(!webSocketReceiveResult.EndOfMessage);
var message = stream.ToArray().Where(b => b != 0).ToArray();
messageReceived(Encoding.ASCII.GetString(message, 0, message.Length));
}
}
}

HttpClient SendAsync with Progress output to Console

I'm simply trying to have a basic SendAsync method write it's progress to the console, and even after a bunch of SO answers for GET, I'm not really seeing how this works for POST.
The file I'm testing with is ~ 100Mb and when it hits the SendAsync method, it sit until complete.
What might I be missing?
var request = new HttpRequestMessage
{
RequestUri = endpoint,
Method = httpMethod,
Content = data
};
var result = string.Empty;
using (var response = await _httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead))
using (var responseStream = await response.Content.ReadAsStreamAsync())
{
int read;
var offset = 0;
var responseBuffer = new byte[1024];
do
{
read = await responseStream.ReadAsync(responseBuffer, 0, responseBuffer.Length);
result += Encoding.UTF8.GetString(responseBuffer, 0, read);
offset += read;
Console.WriteLine($"Offset: {offset}");
} while (read != 0);
response.EnsureSuccessStatusCode();
}
return JsonConvert.DeserializeObject<T>(result);

Read continous bytestream from Stream using TcpClient and Reactive Extensions

Consider the following code:
internal class Program
{
private static void Main(string[] args)
{
var client = new TcpClient();
client.ConnectAsync("localhost", 7105).Wait();
var stream = client.GetStream();
var observable = stream.ReadDataObservable().Repeat();
var s = from d in observable.Buffer(4)
let headerLength = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(d.ToArray(), 2))
let b = observable.Take(headerLength)
select b.ToEnumerable().ToArray();
s.Subscribe(a => Console.WriteLine("{0}", a));
Console.ReadLine();
}
}
public static class Extensions
{
public static IObservable<byte> ReadDataObservable(this Stream stream)
{
return Observable.Defer(async () =>
{
var buffer = new byte[1024];
var readBytes = await stream.ReadAsync(buffer, 0, buffer.Length);
return buffer.Take(readBytes).ToObservable();
});
}
}
Basically I want to parse the messages I receive with Reactive Extensions. The header of the message is parsed correctly using the Buffer(4) and I get the length of the remainder of the message. The problem that arises is that when I do stream.Take(headerLength), the code reevaluates the whole "chain" and tries to get a new message from the stream instead of returning the rest of the bytes which already has been read from the stream. To be more exact, the first ReadAsync(...) returns 38 bytes, the Buffer(4) returns the first 4 of those, the observable.Take(headerLength) does not return the remainding 34 bytes but instead tries to read a new message with ReadAsync.
The question is, how can I make sure the observable.Take(headerLength) receives the already read 34 bytes and not try to read a new message from the stream? I've searched around for a solution, but I can't really figure out how to achieve this.
Edit: This solution (Using Reactive Extensions (Rx) for socket programming practical?) is not what I'm looking for. This isn't reading everything available in the stream (up to buffersize) and makes a continous bytestream out of it. To me this solution doesn't seem like a very efficient way to read from a stream, hence my question.

This approach isn't going to work. The problem is the way you are using the observable. Buffer will not read 4 bytes and quit, it will continually read 4 byte chunks. The Take forms a second subscription that will read overlapping bytes. You'll find it much easier to parse the stream directly into messages.
The following code makes a good deal of effort to clean up properly as well.
Assuming your Message is just this, (ToString added for testing):
public class Message
{
public byte[] PayLoad;
public override string ToString()
{
return Encoding.UTF8.GetString(PayLoad);
}
}
And you have acquired a Stream then you can parse it as follows. First, a method to read an exact number of bytes from a stream:
public async static Task ReadExactBytesAsync(
Stream stream, byte[] buffer, CancellationToken ct)
{
var count = buffer.Length;
var totalBytesRemaining = count;
var totalBytesRead = 0;
while (totalBytesRemaining != 0)
{
var bytesRead = await stream.ReadAsync(
buffer, totalBytesRead, totalBytesRemaining, ct);
ct.ThrowIfCancellationRequested();
totalBytesRead += bytesRead;
totalBytesRemaining -= bytesRead;
}
}
Then the conversion of a stream to IObservable<Message>:
public static IObservable<Message> ReadMessages(
Stream sourceStream,
IScheduler scheduler = null)
{
int subscribed = 0;
scheduler = scheduler ?? Scheduler.Default;
return Observable.Create<Message>(o =>
{
// first check there is only one subscriber
// (multiple stream readers would cause havoc)
int previous = Interlocked.CompareExchange(ref subscribed, 1, 0);
if (previous != 0)
o.OnError(new Exception(
"Only one subscriber is allowed for each stream."));
// we will return a disposable that cleans
// up both the scheduled task below and
// the source stream
var dispose = new CompositeDisposable
{
Disposable.Create(sourceStream.Dispose)
};
// use async scheduling to get nice imperative code
var schedule = scheduler.ScheduleAsync(async (ctrl, ct) =>
{
// store the header here each time
var header = new byte[4];
// loop until cancellation requested
while (!ct.IsCancellationRequested)
{
try
{
// read the exact number of bytes for a header
await ReadExactBytesAsync(sourceStream, header, ct);
}
catch (OperationCanceledException)
{
throw;
}
catch (Exception ex)
{
// pass through any problem in the stream and quit
o.OnError(new InvalidDataException("Error in stream.", ex));
return;
}
ct.ThrowIfCancellationRequested();
var bodyLength = IPAddress.NetworkToHostOrder(
BitConverter.ToInt16(header, 2));
// create buffer to read the message
var payload = new byte[bodyLength];
// read exact bytes as before
try
{
await ReadExactBytesAsync(sourceStream, payload, ct);
}
catch (OperationCanceledException)
{
throw;
}
catch (Exception ex)
{
o.OnError(new InvalidDataException("Error in stream.", ex));
return;
}
// create a new message and send it to client
var message = new Message { PayLoad = payload };
o.OnNext(message);
}
// wrap things up
ct.ThrowIfCancellationRequested();
o.OnCompleted();
});
// return the suscription handle
dispose.Add(schedule);
return dispose;
});
}
EDIT - Very hacky test code I used:
private static void Main(string[] args)
{
var listener = new TcpListener(IPAddress.Any, 12873);
listener.Start();
var listenTask = listener.AcceptTcpClientAsync();
listenTask.ContinueWith((Task<TcpClient> t) =>
{
var client = t.Result;
var stream = client.GetStream();
const string messageText = "Hello World!";
var body = Encoding.UTF8.GetBytes(messageText);
var header = BitConverter.GetBytes(
IPAddress.HostToNetworkOrder(body.Length));
for (int i = 0; i < 5; i++)
{
stream.Write(header, 0, 4);
stream.Write(body, 0, 4);
stream.Flush();
// deliberate nasty delay
Thread.Sleep(2000);
stream.Write(body, 4, body.Length - 4);
stream.Flush();
}
stream.Close();
listener.Stop();
});
var tcpClient = new TcpClient();
tcpClient.Connect(new IPEndPoint(IPAddress.Loopback, 12873));
var clientStream = tcpClient.GetStream();
ReadMessages(clientStream).Subscribe(
Console.WriteLine,
ex => Console.WriteLine("Error: " + ex.Message),
() => Console.WriteLine("Done!"));
Console.ReadLine();
}
Wrapping up
You need to think about setting a timeout for reads, in case the server dies, and some kind of "end message" should be sent by the server. Currently this method will just continually tries to receive bytes. As you haven't specced it, I haven't included anything like this - but if you do, then as I've written it just breaking out of the while loop will cause OnCompleted to be sent.

I guess what is needed here is Qactive: A Rx.Net based queryable reactive tcp server provider
Server
Observable
.Interval(TimeSpan.FromSeconds(1))
.ServeQbservableTcp(new IPEndPoint(IPAddress.Loopback, 3205))
.Subscribe();
Client
var datasourceAddress = new IPEndPoint(IPAddress.Loopback, 3205);
var datasource = new TcpQbservableClient<long>(datasourceAddress);
(
from value in datasource.Query()
//The code below is actually executed on the server
where value <= 5 || value >= 8
select value
)
.Subscribe(Console.WriteLine);
What´s mind blowing about this is that clients can say what and how frequently they want the data they receive and the server can still limit and control when, how frequent and how much data it returns.
For more info on this https://github.com/RxDave/Qactive
Another blog.sample
https://sachabarbs.wordpress.com/2016/12/23/rx-over-the-wire/