A fork of the [ESPAsyncWebServer](https://github.com/me-no-dev/ESPAsyncWebServer) library by [@me-no-dev](https://github.com/me-no-dev) for [ESPHome](https://esphome.io).
For help and support [](https://gitter.im/me-no-dev/ESPAsyncWebServer?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
Async HTTP and WebSocket Server for ESP8266 Arduino
For ESP8266 it requires [ESPAsyncTCP](https://github.com/me-no-dev/ESPAsyncTCP)
To use this library you might need to have the latest git versions of [ESP8266](https://github.com/esp8266/Arduino) Arduino Core
For ESP32 it requires [AsyncTCP](https://github.com/me-no-dev/AsyncTCP) to work
To use this library you might need to have the latest git versions of [ESP32](https://github.com/espressif/arduino-esp32) Arduino Core
## Table of contents
- [ESPAsyncWebServer](#espasyncwebserver)
- [Table of contents](#table-of-contents)
- [Installation](#installation)
- [Using PlatformIO](#using-platformio)
- [Why should you care](#why-should-you-care)
- [Important things to remember](#important-things-to-remember)
- [Principles of operation](#principles-of-operation)
- [The Async Web server](#the-async-web-server)
- [Request Life Cycle](#request-life-cycle)
- [Rewrites and how do they work](#rewrites-and-how-do-they-work)
- [Handlers and how do they work](#handlers-and-how-do-they-work)
- [Responses and how do they work](#responses-and-how-do-they-work)
- [Template processing](#template-processing)
- [Libraries and projects that use AsyncWebServer](#libraries-and-projects-that-use-asyncwebserver)
- [Request Variables](#request-variables)
- [Common Variables](#common-variables)
- [Headers](#headers)
- [GET, POST and FILE parameters](#get-post-and-file-parameters)
- [FILE Upload handling](#file-upload-handling)
- [Body data handling](#body-data-handling)
- [JSON body handling with ArduinoJson](#json-body-handling-with-arduinojson)
- [Responses](#responses)
- [Redirect to another URL](#redirect-to-another-url)
- [Basic response with HTTP Code](#basic-response-with-http-code)
- [Basic response with HTTP Code and extra headers](#basic-response-with-http-code-and-extra-headers)
- [Basic response with string content](#basic-response-with-string-content)
- [Basic response with string content and extra headers](#basic-response-with-string-content-and-extra-headers)
- [Send large webpage from PROGMEM](#send-large-webpage-from-progmem)
- [Send large webpage from PROGMEM and extra headers](#send-large-webpage-from-progmem-and-extra-headers)
- [Send large webpage from PROGMEM containing templates](#send-large-webpage-from-progmem-containing-templates)
- [Send large webpage from PROGMEM containing templates and extra headers](#send-large-webpage-from-progmem-containing-templates-and-extra-headers)
- [Send binary content from PROGMEM](#send-binary-content-from-progmem)
- [Respond with content coming from a Stream](#respond-with-content-coming-from-a-stream)
- [Respond with content coming from a Stream and extra headers](#respond-with-content-coming-from-a-stream-and-extra-headers)
- [Respond with content coming from a Stream containing templates](#respond-with-content-coming-from-a-stream-containing-templates)
- [Respond with content coming from a Stream containing templates and extra headers](#respond-with-content-coming-from-a-stream-containing-templates-and-extra-headers)
- [Respond with content coming from a File](#respond-with-content-coming-from-a-file)
- [Respond with content coming from a File and extra headers](#respond-with-content-coming-from-a-file-and-extra-headers)
- [Respond with content coming from a File containing templates](#respond-with-content-coming-from-a-file-containing-templates)
- [Respond with content using a callback](#respond-with-content-using-a-callback)
- [Respond with content using a callback and extra headers](#respond-with-content-using-a-callback-and-extra-headers)
- [Respond with content using a callback containing templates](#respond-with-content-using-a-callback-containing-templates)
- [Respond with content using a callback containing templates and extra headers](#respond-with-content-using-a-callback-containing-templates-and-extra-headers)
- [Respond with content using a callback without content length to HTTP/1.0 clients](#respond-with-content-using-a-callback-without-content-length-to-http10-clients)
[PlatformIO](http://platformio.org) is an open source ecosystem for IoT development with cross platform build system, library manager and full support for Espressif ESP8266/ESP32 development. It works on the popular host OS: Mac OS X, Windows, Linux 32/64, Linux ARM (like Raspberry Pi, BeagleBone, CubieBoard).
2. Create new project using "PlatformIO Home > New Project"
3. Update dev/platform to staging version:
- [Instruction for Espressif 8266](http://docs.platformio.org/en/latest/platforms/espressif8266.html#using-arduino-framework-with-staging-version)
- [Instruction for Espressif 32](http://docs.platformio.org/en/latest/platforms/espressif32.html#using-arduino-framework-with-staging-version)
4. Add "ESP Async WebServer" to project using [Project Configuration File `platformio.ini`](http://docs.platformio.org/page/projectconf.html) and [lib_deps](http://docs.platformio.org/page/projectconf/section_env_library.html#lib-deps) option:
```ini
[env:myboard]
platform = espressif...
board = ...
framework = arduino
# using the latest stable version
lib_deps = ESP Async WebServer
# or using GIT Url (the latest development version)
- Using asynchronous network means that you can handle more than one connection at the same time
- You are called once the request is ready and parsed
- When you send the response, you are immediately ready to handle other connections
while the server is taking care of sending the response in the background
- Speed is OMG
- Easy to use API, HTTP Basic and Digest MD5 Authentication (default), ChunkedResponse
- Easily extendible to handle any type of content
- Supports Continue 100
- Async WebSocket plugin offering different locations without extra servers or ports
- Async EventSource (Server-Sent Events) plugin to send events to the browser
- URL Rewrite plugin for conditional and permanent url rewrites
- ServeStatic plugin that supports cache, Last-Modified, default index and more
- Simple template processing engine to handle templates
## Important things to remember
- This is fully asynchronous server and as such does not run on the loop thread.
- You can not use yield or delay or any function that uses them inside the callbacks
- The server is smart enough to know when to close the connection and free resources
- You can not send more than one response to a single request
## Principles of operation
### The Async Web server
- Listens for connections
- Wraps the new clients into ```Request```
- Keeps track of clients and cleans memory
- Manages ```Rewrites``` and apply them on the request url
- Manages ```Handlers``` and attaches them to Requests
### Request Life Cycle
- TCP connection is received by the server
- The connection is wrapped inside ```Request``` object
- When the request head is received (type, url, get params, http version and host),
the server goes through all ```Rewrites``` (in the order they were added) to rewrite the url and inject query parameters,
next, it goes through all attached ```Handlers```(in the order they were added) trying to find one
that ```canHandle``` the given request. If none are found, the default(catch-all) handler is attached.
- The rest of the request is received, calling the ```handleUpload``` or ```handleBody``` methods of the ```Handler``` if they are needed (POST+File/Body)
- When the whole request is parsed, the result is given to the ```handleRequest``` method of the ```Handler``` and is ready to be responded to
- In the ```handleRequest``` method, to the ```Request``` is attached a ```Response``` object (see below) that will serve the response data back to the client
- When the ```Response``` is sent, the client is closed and freed from the memory
### Rewrites and how do they work
- The ```Rewrites``` are used to rewrite the request url and/or inject get parameters for a specific request url path.
- All ```Rewrites``` are evaluated on the request in the order they have been added to the server.
- The ```Rewrite``` will change the request url only if the request url (excluding get parameters) is fully match
the rewrite url, and when the optional ```Filter``` callback return true.
- Setting a ```Filter``` to the ```Rewrite``` enables to control when to apply the rewrite, decision can be based on
request url, http version, request host/port/target host, get parameters or the request client's localIP or remoteIP.
- Two filter callbacks are provided: ```ON_AP_FILTER``` to execute the rewrite when request is made to the AP interface,
```ON_STA_FILTER``` to execute the rewrite when request is made to the STA interface.
- The ```Rewrite``` can specify a target url with optional get parameters, e.g. ```/to-url?with=params```
### Handlers and how do they work
- The ```Handlers``` are used for executing specific actions to particular requests
- One ```Handler``` instance can be attached to any request and lives together with the server
- Setting a ```Filter``` to the ```Handler``` enables to control when to apply the handler, decision can be based on
request url, http version, request host/port/target host, get parameters or the request client's localIP or remoteIP.
- Two filter callbacks are provided: ```ON_AP_FILTER``` to execute the rewrite when request is made to the AP interface,
```ON_STA_FILTER``` to execute the rewrite when request is made to the STA interface.
- The ```canHandle``` method is used for handler specific control on whether the requests can be handled
and for declaring any interesting headers that the ```Request``` should parse. Decision can be based on request
method, request url, http version, request host/port/target host and get parameters
- Once a ```Handler``` is attached to given ```Request``` (```canHandle``` returned true)
that ```Handler``` takes care to receive any file/data upload and attach a ```Response```
once the ```Request``` has been fully parsed
- ```Handlers``` are evaluated in the order they are attached to the server. The ```canHandle``` is called only
if the ```Filter``` that was set to the ```Handler``` return true.
- The first ```Handler``` that can handle the request is selected, not further ```Filter``` and ```canHandle``` are called.
### Responses and how do they work
- The ```Response``` objects are used to send the response data back to the client
- The ```Response``` object lives with the ```Request``` and is freed on end or disconnect
- Different techniques are used depending on the response type to send the data in packets
returning back almost immediately and sending the next packet when this one is received.
Any time in between is spent to run the user loop and handle other network packets
- Responding asynchronously is probably the most difficult thing for most to understand
- Many different options exist for the user to make responding a background task
- Template processing can be added to most response types.
- Currently it supports only replacing template placeholders with actual values. No conditional processing, cycles, etc.
- Placeholders are delimited with ```%``` symbols. Like this: ```%TEMPLATE_PLACEHOLDER%```.
- It works by extracting placeholder name from response text and passing it to user provided function which should return actual value to be used instead of placeholder.
- Since it's user provided function, it is possible for library users to implement conditional processing and cycles themselves.
- Since it's impossible to know the actual response size after template processing step in advance (and, therefore, to include it in response headers), the response becomes [chunked](#chunked-response).
## Libraries and projects that use AsyncWebServer
- [WebSocketToSerial](https://github.com/hallard/WebSocketToSerial) - Debug serial devices through the web browser
- [Sattrack](https://github.com/Hopperpop/Sattrack) - Track the ISS with ESP8266
- [ESP Radio](https://github.com/Edzelf/Esp-radio) - Icecast radio based on ESP8266 and VS1053
- [VZero](https://github.com/andig/vzero) - the Wireless zero-config controller for volkszaehler.org
- [ESPurna](https://bitbucket.org/xoseperez/espurna) - ESPurna ("spark" in Catalan) is a custom C firmware for ESP8266 based smart switches. It was originally developed with the ITead Sonoff in mind.
- [fauxmoESP](https://bitbucket.org/xoseperez/fauxmoesp) - Belkin WeMo emulator library for ESP8266.
- [ESP-RFID](https://github.com/omersiar/esp-rfid) - MFRC522 RFID Access Control Management project for ESP8266.
If needed, the `_tempObject` field on the request can be used to store a pointer to temporary data (e.g. from the body) associated with the request. If assigned, the pointer will automatically be freed along with the request.
### JSON body handling with ArduinoJson
Endpoints which consume JSON can use a special handler to get ready to use JSON data in the request callback:
```cpp
#include "AsyncJson.h"
#include "ArduinoJson.h"
AsyncCallbackJsonWebHandler* handler = new AsyncCallbackJsonWebHandler("/rest/endpoint", [](AsyncWebServerRequest *request, JsonVariant &json) {
JsonObject& jsonObj = json.as<JsonObject>();
// ...
});
server.addHandler(handler);
```
## Responses
### Redirect to another URL
```cpp
//to local url
request->redirect("/login");
//to external url
request->redirect("http://esp8266.com");
```
### Basic response with HTTP Code
```cpp
request->send(404); //Sends 404 File Not Found
```
### Basic response with HTTP Code and extra headers
```cpp
AsyncWebServerResponse *response = request->beginResponse(404); //Sends 404 File Not Found
response->addHeader("Server","ESP Async Web Server");
request->send(response);
```
### Basic response with string content
```cpp
request->send(200, "text/plain", "Hello World!");
```
### Basic response with string content and extra headers
When sending a web socket message using the above methods a buffer is created. Under certain circumstances you might want to manipulate or populate this buffer directly from your application, for example to prevent unnecessary duplications of the data. This example below shows how to create a buffer and print data to it from an ArduinoJson object then send it.
```cpp
void sendDataWs(AsyncWebSocketClient * client)
{
DynamicJsonBuffer jsonBuffer;
JsonObject& root = jsonBuffer.createObject();
root["a"] = "abc";
root["b"] = "abcd";
root["c"] = "abcde";
root["d"] = "abcdef";
root["e"] = "abcdefg";
size_t len = root.measureLength();
AsyncWebSocketMessageBuffer * buffer = ws.makeBuffer(len); // creates a buffer (len + 1) for you.
if (buffer) {
root.printTo((char *)buffer->get(), len + 1);
if (client) {
client->text(buffer);
} else {
ws.textAll(buffer);
}
}
}
```
### Limiting the number of web socket clients
Browsers sometimes do not correctly close the websocket connection, even when the close() function is called in javascript. This will eventually exhaust the web server's resources and will cause the server to crash. Periodically calling the cleanClients() function from the main loop() function limits the number of clients by closing the oldest client when the maximum number of clients has been exceeded. This can called be every cycle, however, if you wish to use less power, then calling as infrequently as once per second is sufficient.
```cpp
void loop(){
ws.cleanupClients();
}
```
## Async Event Source Plugin
The server includes EventSource (Server-Sent Events) plugin which can be used to send short text events to the browser.
Difference between EventSource and WebSockets is that EventSource is single direction, text-only protocol.
