Simple Node http server and client communication example

simple-server-and-client.js

// Bring in the core HTTP module
var http = require('http')

/////////////////////////
// Server code
/////////////////////////

// The in-memory state. Will be reset every time the server restarts!
var state = 'OFF'

// This function runs whenever the server gets a new message
function messageHandler(request, response) {
  console.log('Message received!')

  // If it's a post method, if the button is being pressed
  if (request.method == 'POST') {
    var message = ''

    request.on('data', function (data) {
      message += data
    })

    request.on('end', function () {
      // Update the state
      if ( message == 'ON' ) {
        state = 'ON'
      } else if ( message == 'OFF' ) {
        state = 'OFF'
      } else {
        console.log('Received unrecognized message', message)
      }
    })
  }

  // If it's a GET request, return the state
  if ( request.method == 'GET' ) {
    response.end(state)
  }
}

// Create the http server instance
var server = http.createServer(messageHandler)

// Starts the server
server.listen(3000, function () {
  console.log('Server listening on port 3000')
})

/////////////////////////
// Client code
/////////////////////////

// Sends an http request
function sendAMessage() {
  // The options for the message
  var options = {
    method: 'POST',
    hostname: 'localhost',
    port: 3000,
  }
  // Creates the http request instance
  var request = http.request(options)

  // Randomly decide whether we're saying on or off
  var message = Math.random() > 0.5 ? 'ON' : 'OFF'
  console.log('Sending a message...', message)

  // Send the message
  request.write(message) // The actual message content

  // Close the request
  request.end()
}

// Send a message every 3 seconds
setInterval(sendAMessage, 3 * 1000)