Solution for https://github.com/probil/vue-socket.io-extended/issues/67

backend.js

const express = require('express');
const app = express();
const server = require('http').Server(app);
const io = require('socket.io')(server);

server.listen(3000);

io.on('connection', function(socket){
  console.log("---------------------------------------------------------")
  console.log('An user connected');
  console.log("---------------------------------------------------------")
  socket.on('disconnect', function(){
    console.log('user disconnected');
  });

  socket.on('emit_method', function(msg){
    console.log('message: ' + msg);
  });

});

front-end.js

import Vue from 'vue'
import VueSocketio from 'vue-socket.io-extended'
import io from 'socket.io-client'


Vue.use(VueSocketio, io('http://localhost:3000'))

const App = {
  render: () => null,
};


new Vue({
  el: '#app',
  template: '<App/>',
  components: { App },
  sockets: {
    connect () {
      console.log('socket connected')
    },
    customEmit (val) {
      console.log('this method was fired by the socket server. eg: io.emit("customEmit", data)', val)
    }
  },
  methods: {
    clickButton (val) {
      // this.$socket is `socket.io-client` instance
      this.$socket.emit('emit_method', val)
    }
  },
  mounted() {
    setTimeout(() => this.clickButton('Hi there'), 5000);
  }
});