bleno - 当外设本身改变特征值时如何实现更新值回调

Question

假设外围设备正在侦听某个套接字或管道，我正在其中发送一个将修改特性的值。如何将更改通知到中央设备？外围设备和中央设备都在 Linux 平台上运行。因为无论为 Linux 设备给出的 Pizza 示例，都只会在中心写入内容时通知中心。假设如果 Bleno 之外的某个程序更改了值，那么我应该在哪里实现updateValueCallback()？是开onSubscribe还是onNotify？

Answer 1

您应该使用该 onSubscribe()事件。

onSubscribe()当中央（GATT 服务器）订阅来自外围设备onNotify()的通知时触发，而在中央订阅后发送通知时触发。

例如，我将我的特征定义如下：

var customCharacteristic = function() {
    bleno.Characteristic.call(this, {
        uuid: 'UUID_HERE',
        properties: ['read', 'notify', '... etc'],
        //Subscribe event
        onSubscribe = function(maxSize, updateValueCallback){
            console.log('subscribe'); //output that we've subscribed
            //Now the central has subscribed, poll something 
            //(the sensor or whatever you're using) every half 
            //second to see if the value has updated
            setInterval(function() {
                //poll sensor or get value or something
                updateValueCallback(new Buffer([VALUE]);
            }, 500);
        },
        //Notify event
        onNotify = function(){
            console.log('notify'); //to show when notification is being sent
        }
    });
}

//Don't forget to deal with when the central unsubscribes, you might want to stop the interval ticker!

大致基于这篇文章，从这里得到一些想法。