Sending OTA updates over WiFi to your ESP8266

Dec 21, 2020

This Christmas, I added a whole bunch of lights powered by 5V power sources. My goal was to switch them on at sunset, and switch them off on sunrise, by using a MOSFET for power control :)

While I was doing this, I wanted to send OTA updates of my Lua files to the ESP8266 via WiFi. For some unknown reason, I couldn’t use luatool.py’s TCP update method.

So, I ended up building my very own OTA update protocol (which turned out to be fun!). To begin, add ota.lua to your project, and invoke it using dofile("ota.lua") in your init.lua:

	— Send OTA updates to remotely update lua scripts on your ESP8266.
	—
	— LICENCE: http://opensource.org/licenses/MIT
	— Created by Jude Pereira <contact@judepereira.com>
	— See https://judepereira.com/blog/sending-ota-updates-over-wifi-to-your-esp8266/

	srv = net.createServer(net.TCP)

	current_file_name = nil

	srv:listen(8080, function(conn)
	conn:on("receive", function(sck, payload)
	if string.sub(payload, 1, 5) == "BEGIN" then
	current_file_name = string.sub(payload, 7)
	file.open(current_file_name, "w")
	file.close()
	sck:send("NodeMCU: Writing to " .. current_file_name .. '…\n')
	elseif string.sub(payload, 1, 4) == "DONE" then
	sck:send("NodeMCU: Wrote file " .. current_file_name .. "!\n")
	current_file_name = nil
	elseif string.sub(payload, 1, 7) == "RESTART" then
	sck:send("NodeMCU: Restart!\n")
	tmr.create():alarm(500, tmr.ALARM_SINGLE, node.restart)
	else
	if file.open(current_file_name, "a+") then
	if file.write(payload) then
	file.close()
	sck:send("ok\n")
	else
	sck:send("NodeMCU: Write failed!\n")
	end
	else
	sck:send("NodeMCU: Open failed!\n")
	end
	end
	end)
	conn:on("sent", function(sck) sck:close() end)
	end)

view raw ota.lua hosted with ❤ by GitHub

Then, to use this shiny new TCP endpoint created on your ESP8266/NodeMCU, create a wrapper shell script:

	#!/bin/bash

	# Wrapper script for sending OTA updates to your ESP8266 running NodeMCU.
	# See https://judepereira.com/blog/sending-ota-updates-over-wifi-to-your-esp8266/

	HOST=192.168.178.25
	PORT=8080

	for i in "$@"; do
	FILE=$i
	echo "Sending $i…"
	echo -n "BEGIN $FILE" \| nc $HOST $PORT
	while read -r line; do
	#echo -n "write: $line … "
	if ! echo "$line" \| nc $HOST $PORT \| grep "ok" &>/dev/null; then
	echo "Write failed! Please retry…"
	exit 1
	fi
	done <"$FILE"

	echo -n "DONE" \| nc $HOST $PORT
	done

	echo -n "RESTART" \| nc $HOST $PORT

view raw ota.sh hosted with ❤ by GitHub

Heads up! Replace HOST with the IP of your NodeMCU.

The wrapper script will automatically trigger a restart at the end. To use the wrapper script:

$ chmod +x ota.sh
$ ./ota.sh file1.lua file2.lua init.lua

And that’s it! OTA update away!