https integration

i have put this configuration to try and use the lets encrypt crt and key:

/**
* This configuration file was built using the 'Node.js server configuration builder'.
* For a more fully commented example see the file nodejs.config.js.example in the root of this module
*/
backendSettings = {
"scheme":"https",
"host":"zxcx.space",
"port":52222,
"key":"/ssl/keys/c8c7f_c95e3_81443afe79f8cd9f4fa393fbd01f3656.key",
"cert":"/ssl/certs/zxcx_space_c8c7f_c95e3_1529045128_71d2502c933ff2d490b0c8ebb673153a.crt",
"resource":"/socket.io",
"publishUrl":"publish",
"serviceKey":"luli",
"backend":{
"port":443,
"host":"zxcx.space",
"messagePath":"/nodejs/message"},
"clientsCanWriteToChannels":false,
"clientsCanWriteToClients":false,
"extensions":"",
"debug":true,
"transports":["websocket",
"polling"],
"jsMinification":true,
"jsEtag":true,
"logLevel":1};

and still when i run: wwwzxcx@zxcx.space [~/public_html/drupal-nodejs]# node app.js
it gives the following error:

fs.js:646
return binding.open(pathModule._makeLong(path), stringToFlags(flags), mode);
^

TypeError: path must be a string or Buffer
at Object.fs.openSync (fs.js:646:18)
at Object.fs.readFileSync (fs.js:551:33)
at Object.server.start (/home/wwwzxcx/public_html/drupal-nodejs/lib/server.js:74:15)
at Object. (/home/wwwzxcx/public_html/drupal-nodejs/app.js:15:8)
at Module._compile (module.js:643:30)
at Object.Module._extensions..js (module.js:654:10)
at Module.load (module.js:556:32)
at tryModuleLoad (module.js:499:12)
at Function.Module._load (module.js:491:3)
at Function.Module.runMain (module.js:684:10)

i dont know what else to do to get nodejs to start working! i also have tried it with no key/crt file and it gives the same error