WebSockets over HTTP/2

NET 7 introduces Websockets over HTTP/2 support for Kestrel, the SignalR JavaScript client, and SignalR with Blazor WebAssembly.

HTTP2

Multiplexing
Server push
Header compression

ref site:

os and browsers support

Windows 10 1607+
TLS 1.2+
browsers

Note: recommended to use Chrome/FireFox

WebSockets

Accept a WebSocket connection as an asynchronous operation
HttpListenerContext.AcceptWebSocketAsync()
Receives data from the WebSocket connection asynchronously
WebSocket.ReceiveAsync()
Sends data over the WebSocket connection asynchronously
WebSocket.SendAsync()
Closes the WebSocket connection as an asynchronous operation
CloseAsync

Enable WebSocket

default

app.UseWebSockets()

options

var webSocketOptions = new WebSocketOptions
{
    KeepAliveInterval = TimeSpan.FromMinutes(2)
};

app.UseWebSockets(webSocketOptions);

Accept WebSocket requests

if (HttpContext.WebSockets.IsWebSocketRequest)
{
    using var webSocket = await HttpContext.WebSockets.AcceptWebSocketAsync();
}

receive messages

var buffer = new byte[1024 * 4];

var receiveResult = await webSocket.ReceiveAsync(
    new ArraySegment<byte>(buffer), CancellationToken.None);

ArraySegment

Array version of substring()

String[] names = { "Adam", "Bruce", "Charles", "Daniel",
                         "Ebenezer", "Francis", "Gilbert",
                         "Henry", "Irving", "John", "Karl",
                         "Lucian", "Michael" };
      var partNames = new ArraySegment<string>(names, 2, 5);

The example displays the following output:

//    Charles
//    Daniel
//    Ebenezer
//    Francis
//    Gilbert

Send messages

var memory = new ReadOnlyMemory<byte>(Encoding.UTF8.GetBytes(str));

await webSocket.SendAsync(
                memory,
                0, // text message
                0, // none
                CancellationToken.None);

ReadOnlyMemory

message

var memory = new ReadOnlyMemory<byte>(Encoding.UTF8.GetBytes(str));

MessageType

Binary

The message is in binary format.

A receive has completed because a close message was received.

Text

The message is clear text.

WebSocketMessageFlags

DisableCompression

Disables compression for the message if compression has been enabled for the WebSocket instance.

EndOfMessage

Indicates that the data in “buffer” is the last part of a message.

None

None

close

await webSocket.CloseAsync(
            1000,  // NormalClosure
            "normal closure",
            CancellationToken.None);

WebSocketCloseStatus

Fields:

1000, 1001, 1002, 1003, 1005, 1007, 1008, 1009, 1010, 1100

Samples

WebSocketController
Operation WebSocket
Program.cs
Enable WebSocket

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