Method callback

packages/engine.io/lib/userver.ts:132–157

(errorCode, errorContext)

    req.res = res;

    const callback = (errorCode, errorContext) => {
      if (errorCode !== undefined) {
        this.emit("connection_error", {
          req,
          code: errorCode,
          message: Server.errorMessages[errorCode],
          context: errorContext,
        });
        this.abortRequest(req.res, errorCode, errorContext);
        return;
      }

      if (req._query.sid) {
        debug("setting new request for existing client");
        // @ts-ignore
        this.clients[req._query.sid].transport.onRequest(req);
      } else {
        const closeConnection = (errorCode, errorContext) =>
          this.abortRequest(res, errorCode, errorContext);
        this.handshake(
          req._query.transport,
          req as unknown as EngineRequest,
          closeConnection,
        );
      }
    };

    this._applyMiddlewares(req, res, (err) => {
      if (err) {