通过网络套接字在通信中处理 CORS

Question

I'm developing a client and server app, that communicate over web-sockets and found that handling CORS only on the web-socket doesn't raise any additional CORS issues, without handling CORS on the server side itself.

Before solving the issue the error on the client side was:

Access to XMLHttpRequest at 'http://localhost:5000/socket.io/?EIO=4&transport=polling&t=NOOM0wp' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

No "Access-Control-Allow-Origin" header on the response object, that appears only if I handle CORS on the server side.

But, on the client side I get an error:

GET http://localhost:5000/socket.io/?EIO=4&transport=polling&t=NOONjI6 net::ERR_CONNECTION_REFUSED

I guess this is a pretty simple issue, still an explanation will be much appreciated.

Answer 1

Use cors configuration.

Refer to Handling CORS .

 var express = require('express') var app = express() var app = express() var server = require('http').createServer(app) var io = require('socket.io')(server, { cors: { origin: "*" // add your own origin, or '*' for any origins allow. } })