Simple TCP server with LUA on ESP8266
Here is a new LUA script example for your ESP8266 running NodeMCU. The script creates a TCP server listening on port 80. Each time you receive data on the server, it toggles the LED connected to the ESP8266 and sends a message back to the client.
If you need help with installing NodeMCU on your ESP8266, here I have a post for the process.
First TCP server example
Let us got through the code in detail and in the end, you will find the full code.
We need to map our GPIO to the correct pins. This was already discussed in the last article.
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gpio0 = 3
gpio2 = 4
Enter your Wi-Fi SSID which you want to use for the connection and also the password for this network.
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ssid = "AP-Name"
password = "password"
Then we define our GPIO0 as the LED output and create a helper variable to save the pin status.
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pinLed = gpio0
pinStatus = 0
gpio.mode(pinLed, gpio.OUTPUT)
This code block sets your module into STATION mode, which can connect to other access points. Then it will configure the Wi-Fi SSID and password. After the configuration, it will enter a loop that runs every 1000 ms. Here we check if the module has an IP which means we are connected to our network and start the main function. If not we will run in this loop as long as we have no IP.
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wifi.setmode(wifi.STATION)
wifi.sta.config(ssid, password)
tmr.alarm(0, 1000, 1, function()
if wifi.sta.getip() == nil then
print("connecting...")
else
print("IP: ", wifi.sta.getip())
tmr.stop(0) -- Stop loop
main() -- Start the main function
end
Now we can create the TCP server.
The net.createServer() lets you create a UDP or TCP server.
With net.TCP we tell the function that we want a TCP server.
We tell the server module to implement a function when we receive a connection on port 80. If this connection receives a payload we start a new function.
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server = net.createServer(net.TCP)
server:listen(80, function(connection)
connection:on("receive", function(connection, payload)
[...]
end)
end)
This is the content of our receiving function. We print our payload, so we can see what happens. Then we send back a string to the connected client. On our board, we toggle the LED to show that the receiving function was called. After all of this, we close the connection.
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print(payload)
connection:send("<p>Hello Browser, I am an ESP-01 Modul</p>")
pinStatus = 1 - pinStatus
gpio.write(pinLed, pinStatus)
connection:close() -- Verbindung trennen
And here the full structured code with comments:
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-- Pin mapping
gpio0 = 3
gpio2 = 4
-- Wifi credentials
ssid = "AP-Name"
password = "password"
-- Helper variables
pinLed = gpio0
pinStatus = 0
-- GPIO setup
gpio.mode(pinLed, gpio.OUTPUT)
-- Wifi setup
wifi.setmode(wifi.STATION)
wifi.sta.config(ssid, password)
-- Connection loop
tmr.alarm(0, 1000, 1, function()
if wifi.sta.getip() == nil then
print("connecting...")
else
print("IP: ", wifi.sta.getip())
tmr.stop(0) -- Stop loop
main() -- Start main function
end
end)
-- Main function
function main()
server = net.createServer(net.TCP)
server:listen(80, function(connection)
connection:on("receive", function(connection, payload)
print(payload)
connection:send("<p>Hello Browser, I am an ESP-01 Modul</p>")
pinStatus = 1 - pinStatus
gpio.write(pinLed, pinStatus)
connection:close() -- Close connection
end)
end)
end
Second TCP server example (URL request)
Because all the initial code is already in the code above, we only look at the main function.
The creation of the TCP server is the same as in the first example.
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function main()
server = net.createServer(net.TCP)
server:listen(80, function(connection)
connection:on("receive", function(connection, payload)
[...]
end)
end)
end
We search for the two strings led_on and led_off in the payload.
If the string is not found, the variable will contain nil.
When both strings are found, the usage information is sent to the client.
If one of the strings was found, we toggle the LED into the requested state and send a confirmation to the client.
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if string.find(payload, "led_on") and string.find(payload, "led_off") then
connection:send("<p>Usage:</br>[IP]/led_on - turn LED on</br>[IP]/led_off - turn LED off</p>")
elseif string.find(payload, "led_on") ~= nil then
connection:send("<p>LED is now on</p>")
pinStatus = 1
gpio.write(pinLed, pinStatus)
elseif string.find(payload, "led_off") ~= nil then
connection:send("<p>LED is now off</p>")
pinStatus = 0
gpio.write(pinLed, pinStatus)
else
connection:send("<p>Command not recognized</p>")
end
Here is the full code:
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-- Pin mapping
gpio0 = 3
gpio2 = 4
-- Wifi credentials
ssid = "AP-Name"
password = "password"
-- Helper variables
pinLed = gpio0
pinStatus = 0
-- GPIO setup
gpio.mode(pinLed, gpio.OUTPUT)
-- Wifi setup
wifi.setmode(wifi.STATION)
wifi.sta.config(ssid, password)
-- Connection loop
tmr.alarm(0, 1000, 1, function()
if wifi.sta.getip() == nil then
print("connecting...")
else
print("IP: ", wifi.sta.getip())
tmr.stop(0) -- Stop loop
main() -- Start main function
end
end)
-- Main function
function main()
server = net.createServer(net.TCP)
server:listen(80, function(connection)
connection:on("receive", function(connection, payload)
if string.find(payload, "led_on") and string.find(payload, "led_off") then
connection:send("<p>Usage:</br>[IP]/led_on - turn LED on</br>[IP]/led_off - turn LED off</p>")
elseif string.find(payload, "led_on") ~= nil then
connection:send("<p>LED is now on</p>")
pinStatus = 1
gpio.write(pinLed, pinStatus)
elseif string.find(payload, "led_off") ~= nil then
connection:send("<p>LED is now off</p>")
pinStatus = 0
gpio.write(pinLed, pinStatus)
else
connection:send("<p>Command not recognized</p>")
end
connection:close() -- Close connection
end)
end)
end