如何在Socket.io中修复cors策略问题“它没有HTTP ok状态”

Question

I'm setting up socket.io server, and there is a problem with a cors policy . For example: If script uses a get request everything works, but while connecting to socket.io server this error shows on console

Access to XMLHttpRequest at ' https://ser.domain.xyz/iotCloud/?EIO=3&transport=polling&t=MdKfMsN ' from origin ' https://www.domain.xyz ' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: It does not have HTTP ok status.

I think it is problem with socket.io. I tried everything but nothing worked.

var server = express();

var app = require('http').Server(server);

const io = new socket(app, {
  path   : "/iotCloud",
  origins: 'https://www.domain.xyz'
})

server.use(function(req, res, next){
  res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,OPTIONS');
  res.header('Access-Control-Allow-Headers', 'Access-Control-Allow-Origin,*');
  res.header('Access-Control-Allow-Credentials', true);
  res.header('Access-Control-Allow-Origin', 'https://www.projectann.xyz');
  next();
})

I also tried this instead of server.use

var corsOptions = {
  origin: 'https://www.domain.xyz',
  credentials: true,
  methods: "GET,HEAD,PUT,PATCH,POST,DELETE,OPTIONS",
  preflightContinue: true,
  optionsSuccessStatus: 204,
}

server.use(cors(corsOptions))

Client - ServiceWorker

importScripts('../cdn/js/socket.io.js');
var es = {};
     es.socket = io("https://ser.domain.xyz",{
        transportOptions: {
            polling: {
                extraHeaders: {
                    server: "AnnIoT",
                    "loginObject": JSON.stringify(m.data)
                  }
            }
        },
        secure: true,
        rejectUnauthorized: false,
        path: '/iotCloud'
      });

I searched everywhere stack,github and even other languages that saw this error.

Answer 1

an easy workaround is to add below code before next()

if (req.method === 'OPTIONS') {
    res.status(200);
} 

so final code will look like

server.use(function(req, res, next){  
   res.header('Access-Control-Allow-Methods',
   'GET,PUT,POST,DELETE,OPTIONS');  
   res.header('Access-Control-Allow-Headers',
   'Access-Control-Allow-Origin,*');  
   res.header('Access-Control-Allow-Credentials', true);  
   res.header('Access-Control-Allow-Origin',
   'https://www.projectann.xyz');
if (req.method === 'OPTIONS') {
    res.status(200);
} next(); })