counter_cast_and_listen.js

import React, { Component } from 'react';
import {connection} from './interface/connection'

export default class App extends React.Component {
  state = {
    counter: 0
  }

  componentDidMount() {
    connection.connect("ws://localhost:8500")

    // Anyone who listen to the following events can trigger the handleMessageFromServer callbacks
    // Cast and Listen may not be performed by the same client
    connection.addListener("add", this.handleAddMessageFromServer) //receive from server
    connection.addListener("substract", this.handleSubstractMessageFromServer) //receive from server
  }

  handleAddMessageFromServer = (result) => { //receive from server and update
    this.setState({counter: result})
  }
  
  handleSubstractMessageFromServer = (result) => { //receive from server and update
    this.setState({counter: result})
  }

  handleAddCast = () => { //send to server
    connection.cast("add", 1)
  }
  
  handleSubstractCast = () => { //send to server
    connection.cast("substract", 1)
  }

  render() {
    return ( 
      <div>
        <button onClick={this.handleAddCast}>+</button>
        <h3>{this.state.counter}</h3>
        <button onClick={this.handleSubstractCast}>-</button>
      </div>
    )
  }

}