WebSocketHandler.cs

using System;
using System.Collections.Concurrent;
using System.IO;
using System.Net.WebSockets;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;

namespace IphoneRemoteCamera
{
    public static class WebSocketHandler
    {
        private static readonly ConcurrentDictionary<Guid, WebSocket> subscribers = new ConcurrentDictionary<Guid, WebSocket>();

        public static async Task HandleAsync(bool isPublisher, WebSocket ws)
        {
            if (isPublisher)
            {
                var buffer = new byte[64 * 1024];
                while (ws.State == WebSocketState.Open)
                {
                    using var ms = new MemoryStream();
                    WebSocketReceiveResult result;
                    do
                    {
                        result = await ws.ReceiveAsync(buffer, CancellationToken.None);
                        if (result.MessageType == WebSocketMessageType.Close) break;
                        ms.Write(buffer, 0, result.Count);
                    } while (!result.EndOfMessage);

                    if (result.MessageType == WebSocketMessageType.Binary)
                    {
                        var data = ms.ToArray();
                        foreach (var sub in subscribers.Values)
                        {
                            if (sub.State == WebSocketState.Open)
                                await sub.SendAsync(data, WebSocketMessageType.Binary, true, CancellationToken.None);
                        }
                    }
                    else if (result.MessageType == WebSocketMessageType.Close)
                    {
                        break;
                    }
                }
            }
            else
            {
                var id = Guid.NewGuid();
                subscribers[id] = ws;
                var ping = new byte[1];
                while (ws.State == WebSocketState.Open)
                {
                    _ = await ws.ReceiveAsync(ping, CancellationToken.None);
                }
                subscribers.TryRemove(id, out _);
            }

            if (ws.State != WebSocketState.Closed)
                await ws.CloseAsync(WebSocketCloseStatus.NormalClosure, "Closing", CancellationToken.None);
        }
    }
}