Detailed explanation of creating NetCore WebSocket instant messaging instance

public class MsgTemplate
 {
 public string SenderID { get; set; }
 public string ReceiverID { get; set; }
 public string MessageType { get; set; }
 public string Content { get; set; }
 }

public class ChatWebSocketMiddleware
 {
 private static ConcurrentDictionary _sockets = new ConcurrentDictionary();

 private readonly RequestDelegate _next;

 public ChatWebSocketMiddleware(RequestDelegate next)
 {
  _next = next;
 }

 public async Task Invoke(HttpContext context)
 {
  if (!context.WebSockets.IsWebSocketRequest)
  {
  await _next.Invoke(context);
  return;
  }
  System.Net.WebSockets.WebSocket dummy;

  CancellationToken ct = context.RequestAborted;
  var currentSocket = await context.WebSockets.AcceptWebSocketAsync();
  //string socketId = Guid.NewGuid().ToString();
  string socketId = context.Request.Query["sid"].ToString();
  if (!_sockets.ContainsKey(socketId))
  {
  _sockets.TryAdd(socketId, currentSocket);
  }
  //_sockets.TryRemove(socketId, out dummy);
  //_sockets.TryAdd(socketId, currentSocket);

  while (true)
  {
  if (ct.IsCancellationRequested)
  {
   break;
  }

  string response = await ReceiveStringAsync(currentSocket, ct);
  MsgTemplate msg = JsonConvert.DeserializeObject(response);

  if (string.IsNullOrEmpty(response))
  {
   if (currentSocket.State != WebSocketState.Open)
   {
   break;
   }

   continue;
  }

  foreach (var socket in _sockets)
  {
   if (socket.Value.State != WebSocketState.Open)
   {
   continue;
   }
   if (socket.Key == msg.ReceiverID || socket.Key == socketId)
   {
   await SendStringAsync(socket.Value, JsonConvert.SerializeObject(msg), ct);
   }
  }
  }

  //_sockets.TryRemove(socketId, out dummy);

  await currentSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Closing", ct);
  currentSocket.Dispose();
 }

 private static Task SendStringAsync(System.Net.WebSockets.WebSocket socket, string data, CancellationToken ct = default(CancellationToken))
 {
  var buffer = Encoding.UTF8.GetBytes(data);
  var segment = new ArraySegment(buffer);
  return socket.SendAsync(segment, WebSocketMessageType.Text, true, ct);
 }

 private static async Task ReceiveStringAsync(System.Net.WebSockets.WebSocket socket, CancellationToken ct = default(CancellationToken))
 {
  var buffer = new ArraySegment(new byte[8192]);
  using (var ms = new MemoryStream())
  {
  WebSocketReceiveResult result;
  do
  {
   ct.ThrowIfCancellationRequested();

   result = await socket.ReceiveAsync(buffer, ct);
   ms.Write(buffer.Array, buffer.Offset, result.Count);
  }
  while (!result.EndOfMessage);

  ms.Seek(0, SeekOrigin.Begin);
  if (result.MessageType != WebSocketMessageType.Text)
  {
   return null;
  }

  using (var reader = new StreamReader(ms, Encoding.UTF8))
  {
   return await reader.ReadToEndAsync();
  }
  }
 }
 }

if (socket.Key == msg.ReceiverID || socket.Key == socketId)
{
 await SendStringAsync(socket.Value,JsonConvert.SerializeObject(msg), ct);
}

app.UseWebSockets();
app.UseMiddleware();

export class Dialog {

 private ws: any;
 private msgArr: Array;

 constructor(private httpService: HttpService) {

 this.msgArr = [];
 }

 ionViewDidEnter() {
 if (!this.ws) {
  this.ws = new WebSocket("ws://localhost:56892?sid=222");

  this.ws.onopen = () => {
  console.log('open');
  };

  this.ws.onmessage = (event) => {
  console.log('new message: ' + event.data);
  var msgObj = JSON.parse(event.data);
  this.msgArr.push(msgObj);;
  };

  this.ws.onerror = () => {
  console.log('error occurred!');
  };

  this.ws.onclose = (event) => {
  console.log('close code=' + event.code);
  };
 }
 }

 sendMsg(msg) {//msg为我要发送的内容 比如"hello world"
 var msgObj = {
  SenderID: "222",
  ReceiverID: "111",
  MessageType: "text",
  Content: msg
 };
 this.ws.send(JSON.stringify(msgObj));
 }