Issue: Failed connection to server on mobile with "connect_error due to xhr poll error"

[EhsanKey]

Hello everyone!

I have developed a project using socket-io-client (Next.js) on the client side and socket-io (Node.js, Express) on the server side. When I run the project on my computer's browser, everything works fine. However, when I try to run the project on a mobile browser, I encounter a connection issue with the following error message: "connect_error due to xhr poll error".

The problem arises during the connection to the server, and the specific error message is as follows:

polling.js:307 GET http://localhost:4000/socket.io/?EIO=4&transport=polling&t=OavGB5H net::ERR_CONNECTION_REFUSED

Here is the client-side code:

socket.start("http://localhost:4000/", {
  autoConnect: false,
  auth: {
    token: getCookie("token"),
  },
});

socket.connect((res) => {
  console.log(res, "socket connected");
});

socket.on("connect_error", (err) => {
  console.log(`connect_error due to ${err.message}`);
});

socket.on("connect", () => {
  console.log("socket connected");
});

socket.on("disconnect", () => {
  console.log("socket disconnected");
});

And here is the server-side code:

const express = require("express");
const http = require("http");
const socketIO = require("socket.io");
const app = express();
const server = http.createServer(app);

const io = socketIO(server, {
  cors: { origin: "*" },
});

// Other code and configurations

io.on("connection", (socket) => {
  console.log("connected");
});

const port = 4000;
server.listen(port, () => {
  console.log(`Server is listening on port ${port}`);
});

If you have any experience or a solution regarding this issue, please share it in this discussion.

Thank you!

[darrachequesne]

Hi! I think that's because you can't use localhost to reach your server on your mobile.

You'll need to be on the same network as your server (wifi) and use the IP address of your server, something like 192.168.0.10.

[EhsanKey]

I have disabled the firewall, and I can view my project on a mobile browser. However, the problem is that it cannot connect to the socket!