小程序服务端，创建一个SOAP Web Server，fs对象读文件报如下错误，请解决。

Error: EACCES: permission denied, open ‘helloservice.wsdl’

    at Object.fs.openSync (fs.js:652:18)

全部代码如下：

var http = require('http');

var soap = require('soap');

var helloService = {

Hello_Service: {

Hello_Port: {

sayHello: function (args) {

return {

greeting: args.name + "Hello!!!"

};

}

}

}

}

var xml = require('fs').readFileSync('helloservice.wsdl', 'utf8'),

server = http.createServer(function (request, response) {

response.end("404: Not Found: " + request.url)

});

server.listen(8000);

soap.listen(server, '/wsdl', helloService, xml);

console.log('Webserver start listen at http://eqeju3pb.qcloud.la:8000/wsdl?wsdl');