ESP32: Simple HTTP-server

This project is a basic HTTP-server capable of receiving http requests and responding accordingly. By default it implements the following HTTP verbs: GET, POST, PUT, PATCH, and DELETE so it can also be easily RESTfull servers.

This server uses the ESP32's oficial development framework (ESP-IDF)

Getting Started

These instructions will get you a copy of the project up and running on your local machine for development and testing purposes.

Prerequisites

What things you need to install the software and how to install them

• The toolchain Guide
• The latest ESP-IDF Github

Running

Before compiling you should first specify the SSID and Password:

#define AP_TARGET_SSID "Your SSID"
#define AP_TARGET_PASSWORD "Your password"

By default the ESP32 is setup to use a dynamic IP. If you wish to use a static IP uncomment, and adjust the following settings:

#define DEVICE_IP          "192.168.178.4"
#define DEVICE_GW          "192.168.178.1"
#define DEVICE_NETMASK     "255.255.255.0"

If the ESP32 has sucesfully connected to the WIFI network you should something like:

I (275) wifi: mode : sta (30:ae:a4:8f:6b:a8)
I (761) wifi: n:4 0, o:1 0, ap:255 255, sta:4 0, prof:1
I (1420) wifi: state: init -> auth (b0)
I (1424) wifi: state: auth -> assoc (0)
I (1428) wifi: state: assoc -> run (10)
I (1460) wifi: connected with 'Your SSID', channel 4
I (1461) wifi: pm start, type: 1

I (3837) event: sta ip: 192.168.178.122, mask: 255.255.255.0, gw: 192.168.178.1

configuration

Starting the server

Like all the examples using the ESP-IDF this server uses freeRTOS. To start the http server you have to create a task that runs the function 'http_server

xTaskCreate(&http_server, "http_server", 2048, NULL, 5, NULL);		// Starts server at port 80
xTaskCreate(&http_server, "http_server", 2048, (void *) 123, 5, NULL);	// Starts server at port 123

Here pvParameters is abbused to pass the desired port to the function (normally this is a pointer, but this is converted back to int in 'http_server'). If pvParameters is left to be NULL it defaults to port 80.

Handling requests

When a request is received the payload is placed in a variable called 'payload'. the following request below results in payload holding the string '/index.html?param1=value1&param2=value2'

GET /index.html?param1=value1&param2=value2 HTTP/1.1
Host: 192.168.178.122:404
Cache-Control: no-cache

As this is a minimal server the actual parsing of the string is not implemented (note that the cJSON library is suplied with the ESP_IDF, so parsing json can be implemented quite easily).

before sending data or properly terminate a connection, the ESP32 should always send a html header containing the http status code. This is done with netconn_write(conn, HDR_200, sizeof(HDR_200)-1, NETCONN_NOCOPY);

The implemented http status codes are:

• HDR_200 'OK'
• HDR_201 'created'
• HDR_204 'No content'
• HDR_404 'Not found'
• HDR_405 'Method not allowed'
• HDR_409 'conflict'
• HDR_501 'Not implemented'

the selection is based on the REST API tutorial but can easily be extended.

to reply with data (consecutive) calls to netconn_write(conn, "html code as string", sizeof("html code as string")-1, NETCONN_NOCOPY); can be made.