A websocket's ReceiveAsync method does not await the entire message

Question

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

Answer 1

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.

Answer 2

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;
}

Answer 3

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).

Answer 4

// 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);

Answer 5

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