Method _add

packages/socket.io/lib/namespace.ts:335–380

* Adds a new client. * * @return {Socket} * @private

(
    client: Client<ListenEvents, EmitEvents, ServerSideEvents>,
    auth: Record<string, unknown>,
    fn: (
      socket: Socket<ListenEvents, EmitEvents, ServerSideEvents, SocketData>,
    ) => void,
  )

   * @private
   */
  async _add(
    client: Client<ListenEvents, EmitEvents, ServerSideEvents>,
    auth: Record<string, unknown>,
    fn: (
      socket: Socket<ListenEvents, EmitEvents, ServerSideEvents, SocketData>,
    ) => void,
  ) {
    debug("adding socket to nsp %s", this.name);
    const socket = await this._createSocket(client, auth);

    this._preConnectSockets.set(socket.id, socket);

    if (
      // @ts-ignore
      this.server.opts.connectionStateRecovery?.skipMiddlewares &&
      socket.recovered &&
      client.conn.readyState === "open"
    ) {
      return this._doConnect(socket, fn);
    }

    this.run(socket, (err) => {
      process.nextTick(() => {
        if ("open" !== client.conn.readyState) {
          debug("next called after client was closed - ignoring socket");
          socket._cleanup();
          return;
        }

        if (err) {
          debug("middleware error, sending CONNECT_ERROR packet to the client");
          socket._cleanup();
          if (client.conn.protocol === 3) {
            return socket._error(err.data || err.message);
          } else {
            return socket._error({
              message: err.message,
              data: err.data,
            });
          }
        }

        this._doConnect(socket, fn);
      });
    });
  }

  private async _createSocket(
    client: Client<ListenEvents, EmitEvents, ServerSideEvents>,