asp.net – signalR – 如何从客户端调用服务器方法 – 代码无法

“undefined” is not a function

在线聊天.SendNewOrderConfirmation(数据);
有谁知道为什么会这样？
谢谢

在服务器端

public class DriverChat : Hub,IDisconnect
{

    public void Start(Driver d)
    {
     ...
     }
    public void SendNewOrderConfirmation(OrderDriverData data)
    {
        LogFile.LogResponseTime(data.orderId,data.driverId);
    }
}

在客户端

function begin(args) {

        try {
            //alert('begin');

            chat = $.connection.driverChat;

            chat.refresh = function () {
                ready++;
            };
            chat.disconnect = function () {
                alert('Server has disconnected');
            };
            $.connection.hub.start(function () {
                chat.start(args);
                ready++;
               // alert('signalR started');
            });
         } catch (e) {
            alert(e.message);
            return e.message;
        }
    }
    function confirmNewOrder(data) {
        try{
            alert('sending cofirmation');
            chat.SendNewOrderConfirmation(data);
            alert('confirmation sent');
        } catch (e) {
            alert(e);
        }
    };
}