Sockit.io can not connect to server by React Native - react-native

Question

I use the library socket.io-client": "2.3.0" try to use sockit on React Native.
I try the simple code on server side.
server.js
const
io = require("socket.io"),
server = io.listen(8000);
let
sequenceNumberByClient = new Map();
// event fired every time a new client connects:
server.on("connection", (socket) => {
console.info(`Client connected [id=${socket.id}]`);
// initialize this client's sequence number
sequenceNumberByClient.set(socket, 1);
// when socket disconnects, remove it from the list:
socket.on("disconnect", () => {
sequenceNumberByClient.delete(socket);
console.info(`Client gone [id=${socket.id}]`);
});
});
// sends each client its current sequence number
setInterval(() => {
for (const [client, sequenceNumber] of sequenceNumberByClient.entries()) {
client.emit("seq-num", sequenceNumber);
sequenceNumberByClient.set(client, sequenceNumber + 1);
}
}, 1000);
on client side:
client.js
const
io = require("socket.io-client"),
ioClient = io.connect("http://localhost:8000");
ioClient.on("seq-num", (msg) => console.info(msg));
node server and then node client
I can see Client connected on server side.
But it is not working on my React Native side even on Android or IOS.
My React Native code like this:
import io from 'socket.io-client';
const ioClient = io.connect("http://localhost:8000");
ioClient.on('connect', () => console.log('connected on React Native'));
ioClient.on("seq-num", (msg) => console.info(msg));
I can't see connected on React Native and nothing happened on my server.
Any help would be appreciated.