使用 Node.js 和 COAP 协议构建物联网应用程序 - 实时时间数据传输示例

以下是使用 Node.js 实现物联网应用程序的代码，使用 COAP 通信协议，服务端监听客户端的请求，每隔一毫秒发送当前时间的字符串。当服务器有新的响应数据时，客户端将其打印到控制台上。

服务端代码：

const coap = require('coap');
const server = coap.createServer();

server.on('request', function(req, res) {
  console.log('Received request: ' + req.method + ' ' + req.url);
  
  setInterval(() => {
    res.end(new Date().toString());
  }, 1);
});

server.listen(function() {
  console.log('Server started');
});

客户端代码：

const coap = require('coap');
const client = coap.request('coap://localhost');

client.on('response', function(res) {
  console.log('Received response: ' + res.payload.toString());
});

client.end();

运行以上代码，客户端会不断输出当前时间的字符串。可以使用命令行工具观察输出结果：

$ node client.js
Received response: Thu Oct 07 2021 16:41:00 GMT-0700 (Pacific Daylight Time)
Received response: Thu Oct 07 2021 16:41:01 GMT-0700 (Pacific Daylight Time)
Received response: Thu Oct 07 2021 16:41:02 GMT-0700 (Pacific Daylight Time)
Received response: Thu Oct 07 2021 16:41:03 GMT-0700 (Pacific Daylight Time)
...