请教一下熟悉nodejs和CoAP、DTLS的同学

[抽搐人偶师]

想要实现CoAP利用DTLS进行安全通信，这是down的别的大佬的源码，但是服务器和客户端无论如何都连接不上，求一个解决方法，是不是证书有问题？？
服务器：

const coap    = require('coap') // or coap
const path    = require('path');

//var SegfaultHandler = require('segfault-handler');

//SegfaultHandler.registerHandler("crash.log"); // With no argument, SegfaultHandler will generate a generic log file name

const dtls_opts = {
  key: path.join(__dirname, '../test/private.der'),
  debug: 1,
  handshakeTimeoutMin: 3000
};


const server  = coap.createServer(
  {
    dtls: dtls_opts,
    port: 5684,
  }
);

server.on('request', function(req, res) {
  console.log('request arrives:\n'+JSON.stringify(req));
  res.end('Hello ' + req.url.split('/')[1] + '\n')
})

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

客户端：

var coap = require('coap') // or coap


//var SegfaultHandler = require('segfault-handler');

//SegfaultHandler.registerHandler("crash.log"); // With no argument, SegfaultHandler will generate a generic log file name

var dtls_opts = {
//  psk:           new Buffer('AAAAAAAAAAAAAAAA'),
//  PSKIdent:      new Buffer("32323232-3232-3232-3232-323232323232"),
  psk:           Buffer.from("AAAAAAAAAAAAAAAA"),
  PSKIdent:      Buffer.from("32323232-3232-3232-3232-323232323232"),
  key:           null,
  peerPublicKey: null
};

var req = coap.request('coaps://127.0.0.1:5684/client',
                        dtls_opts,
                       (req) => {
                          req.on('response', function(res) {
                            res.pipe(process.stdout)
                          });
                          req.end();
                        }
                      );

[skycobry]

请问，你最后测试 CoAP DTLS成功了么