var connection = new signalR.HubConnectionBuilder().withUrl(hubUrl).build();
var connectionId;
function connect() {
    console.log('check connection state :' + connection.state);
    if (connection.state === signalR.HubConnectionState.Disconnected) {
        connection.start().then(function () {
            console.log('connect successful');
        }).catch(function () {
            console.log('connect failed');
            setTimeout(connect,5000);
        });
    }
}
connection.onclose(function () {
    console.log('connect closed');
    connect();
});
connection.on('Connected', function (id) {
    connectionId = id;
    console.log('signalR 连接Id:' + connectionId);
});
connection.on("ServerToClient", function (method, message, to, from) {
    console.log(method + ':' + message);
    onMessage(method, message, to, from);
});