How To Send Text Messages From The ESP8266 and Twilio Using NodeMcu

Step 1: Create a Twilio Account

Head over to Twilio.com and create a free or paid account. In your account dashboard find your Account SID and Token and save them as will need it in the code.

Step 2: Make a POST Request to IoT HTTPS Relay

IoT HTTPS Relay is a Google App Engine app I created for relaying information between HTTP and HTTPS. Since Twilio does not allow access to their APIs via HTTP, and since the ESP module does not support HTTPS, IoT HTTPS Relay receives the HTTP request from the ESP8266 and changes it to an HTTPS.

The POST request to send a text message is the following:

POST /twilio/Messages.json HTTP/1.1
Host: iot-https-relay.appspot.com
Connection: close
Content-Type: application/x-www-form-urlencoded
Content-Length: xxx

token=xxxxxx&From=15558689998&To=19998675584&Body=myURLEncodedMessage&sid=xxxxxx

Where the “token” and “sid” parameters are your Twilio’s account Account SID and Token values from step 1. The “From” and “To” parameters are your Twilio’s given phone number, and the destination phone number respectively. Please remember that if you a free Twilio account the “To” phone number can only be your Twilio verified phone.

The “Body” parameter is the body of the text messages.

Step 3: NodeMcu Text Message Code

If your ESP8266 has the NodeMcu firmware installed you can use the script below to automate the SMS process.

-- Your access point's SSID and password
local SSID = "xxxxxx"
local SSID_PASSWORD = "xxxxxx"
 
-- configure ESP as a station
wifi.setmode(wifi.STATION)
wifi.sta.config(SSID,SSID_PASSWORD)
wifi.sta.autoconnect(1)
 
local TWILIO_ACCOUNT_SID = "xxxxxx"
local TWILIO_TOKEN = "xxxxxx"
 
local HOST = "iot-https-relay.appspot.com" 
local URI = "/twilio/Messages.json"
 
function build_post_request(host, uri, data_table)
 
     local data = ""
     
     for param,value in pairs(data_table) do
          data = data .. param.."="..value.."&"
     end
 
     request = "POST "..uri.." HTTP/1.1\r\n"..
     "Host: "..host.."\r\n"..
     "Connection: close\r\n"..
     "Content-Type: application/x-www-form-urlencoded\r\n"..
     "Content-Length: "..string.len(data).."\r\n"..
     "\r\n"..
     data
 
     print(request)
     
     return request
end
 
local function display(sck,response)
     print(response)
end
 
-- When using send_sms: the "from" number HAS to be your twilio number.
-- If you have a free twilio account the "to" number HAS to be your twilio verified number.
-- The numbers MUST include the country code.
-- DO NOT add the "+" sign.
local function send_sms(from,to,body)
 
     local data = {
      sid = TWILIO_ACCOUNT_SID,
      token = TWILIO_TOKEN,
      Body = string.gsub(body," ","+"),
      From = from,
      To = to
     }
     
     socket = net.createConnection(net.TCP,0)
     socket:on("receive",display)
     socket:connect(80,HOST)
 
     socket:on("connection",function(sck) 
       
          local post_request = build_post_request(HOST,URI,data)
          sck:send(post_request)
     end)     
end
 
function check_wifi()
 local ip = wifi.sta.getip()
 
 if(ip==nil) then
   print("Connecting...")
 else
  tmr.stop(0)
  print("Connected to AP!")
  print(ip)
  send_sms("15551234567","12223456789","Hello from your ESP8266") 
 end
 
end
 
tmr.alarm(0,2000,1,check_wifi)