[CoAP] Exposing multiple Things on the same Servient produces an Error

[FadySalama]

When I try to add multiple CoAP devices to the same servient defined like this

const coapServient = new Servient()
coapServient.addServer(new CoapServer({
    port: 5683
}))

it causes this error to occur

Error: getsockname EBADF
    at Socket.address (node:dgram:775:11)
    at CoapServer.getPort (/node_modules/@node-wot/binding-coap/dist/coap-server.js:104:27)
    at CoapServer.<anonymous> (/node_modules/@node-wot/binding-coap/dist/coap-server.js:112:31)
    at Generator.next (<anonymous>)
    at /node_modules/@node-wot/binding-coap/dist/coap-server.js:31:71
    at new Promise (<anonymous>)
    at __awaiter (/node_modules/@node-wot/binding-coap/dist/coap-server.js:27:12)
    at CoapServer.expose (/node_modules/@node-wot/binding-coap/dist/coap-server.js:111:16)
    at /node_modules/@node-wot/core/dist/servient.js:51:40
    at Array.forEach (<anonymous>) {
  errno: -9,
  code: 'EBADF',
  syscall: 'getsockname'
}

The error does not happen if I expose only 1 CoAP device and only happens with CoAP. (I run the same code to generate HTTP instances as well and it works flawlessly). I was able to replicate the error in a Windows environment and in a dockerized Ubuntu environment running an Ubuntu host.

[FadySalama]

A small update: I found what was causing this issue. I was calling servient.start() for each new device added to get the WoT object which did break things severely for CoAP and not so severely for HTTP. By calling servient.start() only once, the issues were solved and I could add multiple CoAP devices without any issues.
The problem is, there is nothing stopping me from calling servient.start() multiple times. How about ensuring that calling servient.start() always returns exactly one WoT object using a singleton pattern? Otherwise, I think it is safe to close this issue.

[danielpeintner]

I opened #1195 which prevents a Servient to be started a second time.

Hence in your case you would get an error ("Servient started already") the second time.
Does this make sense?