esp-idf/examples/protocols/asio/async_request/main/async_http_request.cpp

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/*
* SPDX-FileCopyrightText: 2021 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: CC0-1.0
*
* ASIO HTTP request example
*/
#include <string>
#include <array>
#include <asio.hpp>
#include <memory>
#include <system_error>
#include <utility>
#include "esp_log.h"
#include "nvs_flash.h"
#include "esp_event.h"
#include "protocol_examples_common.h"
constexpr auto TAG = "async_request";
using asio::ip::tcp;
namespace {
void esp_init()
{
ESP_ERROR_CHECK(nvs_flash_init());
ESP_ERROR_CHECK(esp_netif_init());
ESP_ERROR_CHECK(esp_event_loop_create_default());
esp_log_level_set("async_request", ESP_LOG_DEBUG);
/* This helper function configures Wi-Fi or Ethernet, as selected in menuconfig.
* Read "Establishing Wi-Fi or Ethernet Connection" section in
* examples/protocols/README.md for more information about this function.
*/
ESP_ERROR_CHECK(example_connect());
}
/**
* @brief Simple class to add the resolver to a chain of actions
*
*/
class AddressResolution : public std::enable_shared_from_this<AddressResolution> {
public:
explicit AddressResolution(asio::io_context &context) : ctx(context), resolver(ctx) {}
/**
* @brief Initiator function for the address resolution
*
* @tparam CompletionToken callable responsible to use the results.
*
* @param host Host address
* @param port Port for the target, must be number due to a limitation on lwip.
*/
template<class CompletionToken>
void resolve(const std::string &host, const std::string &port, CompletionToken &&completion_handler)
{
auto self(shared_from_this());
resolver.async_resolve(host, port, [self, completion_handler](const asio::error_code & error, tcp::resolver::results_type results) {
if (error) {
ESP_LOGE(TAG, "Failed to resolve: %s", error.message().c_str());
return;
}
completion_handler(self, results);
});
}
private:
asio::io_context &ctx;
tcp::resolver resolver;
};
/**
* @brief Connection class
*
* The lowest level dependency on our asynchronous task, Connection provide an interface to TCP sockets.
* A similar class could be provided for a TLS connection.
*
* @note: All read and write operations are written on an explicit strand, even though an implicit strand
* occurs in this example since we run the io context in a single task.
*
*/
class Connection : public std::enable_shared_from_this<Connection> {
public:
explicit Connection(asio::io_context &context) : ctx(context), strand(context), socket(ctx) {}
/**
* @brief Start the connection
*
* Async operation to start a connection. As the final act of the process the Connection class pass a
* std::shared_ptr of itself to the completion_handler.
* Since it uses std::shared_ptr as an automatic control of its lifetime this class must be created
* through a std::make_shared call.
*
* @tparam completion_handler A callable to act as the final handler for the process.
* @param host host address
* @param port port number - due to a limitation on lwip implementation this should be the number not the
* service name tipically seen in ASIO examples.
*
* @note The class could be modified to store the completion handler, as a member variable, instead of
* pass it along asynchronous calls to allow the process to run again completely.
*
*/
template<class CompletionToken>
void start(tcp::resolver::results_type results, CompletionToken &&completion_handler)
{
connect(results, completion_handler);
}
/**
* @brief Start an async write on the socket
*
* @tparam data
* @tparam completion_handler A callable to act as the final handler for the process.
*
*/
template<class DataType, class CompletionToken>
void write_async(const DataType &data, CompletionToken &&completion_handler)
{
asio::async_write(socket, data, asio::bind_executor(strand, completion_handler));
}
/**
* @brief Start an async read on the socket
*
* @tparam data
* @tparam completion_handler A callable to act as the final handler for the process.
*
*/
template<class DataBuffer, class CompletionToken>
void read_async(DataBuffer &&in_data, CompletionToken &&completion_handler)
{
asio::async_read(socket, in_data, asio::bind_executor(strand, completion_handler));
}
private:
template<class CompletionToken>
void connect(tcp::resolver::results_type results, CompletionToken &&completion_handler)
{
auto self(shared_from_this());
asio::async_connect(socket, results, [self, completion_handler](const asio::error_code & error, [[maybe_unused]] const tcp::endpoint & endpoint) {
if (error) {
ESP_LOGE(TAG, "Failed to connect: %s", error.message().c_str());
return;
}
completion_handler(self);
});
}
asio::io_context &ctx;
asio::io_context::strand strand;
tcp::socket socket;
};
} // namespace
namespace Http {
enum class Method { GET };
/**
* @brief Simple HTTP request class
*
* The user needs to write the request information direct to header and body fields.
*
* Only GET verb is provided.
*
*/
class Request {
public:
Request(Method method, std::string host, std::string port, const std::string &target) : host_data(std::move(host)), port_data(std::move(port))
{
header_data.append("GET ");
header_data.append(target);
header_data.append(" HTTP/1.1");
header_data.append("\r\n");
header_data.append("Host: ");
header_data.append(host_data);
header_data.append("\r\n");
header_data.append("\r\n");
};
void set_header_field(std::string const &field)
{
header_data.append(field);
}
void append_to_body(std::string const &data)
{
body_data.append(data);
};
const std::string &host() const
{
return host_data;
}
const std::string &service_port() const
{
return port_data;
}
const std::string &header() const
{
return header_data;
}
const std::string &body() const
{
return body_data;
}
private:
std::string host_data;
std::string port_data;
std::string header_data;
std::string body_data;
};
/**
* @brief Simple HTTP response class
*
* The response is built from received data and only parsed to split header and body.
*
* A copy of the received data is kept.
*
*/
struct Response {
/**
* @brief Construct a response from a contiguous buffer.
*
* Simple http parsing.
*
*/
template<class DataIt>
explicit Response(DataIt data, size_t size)
{
raw_response = std::string(data, size);
auto header_last = raw_response.find("\r\n\r\n");
if (header_last != std::string::npos) {
header = raw_response.substr(0, header_last);
}
body = raw_response.substr(header_last + 3);
}
/**
* @brief Print response content.
*/
void print()
{
ESP_LOGI(TAG, "Header :\n %s", header.c_str());
ESP_LOGI(TAG, "Body : \n %s", body.c_str());
}
std::string raw_response;
std::string header;
std::string body;
};
/** @brief HTTP Session
*
* Session class to handle HTTP protocol implementation.
*
*/
class Session : public std::enable_shared_from_this<Session> {
public:
explicit Session(std::shared_ptr<Connection> connection_in) : connection(std::move(connection_in))
{
}
template<class CompletionToken>
void send_request(const Request &request, CompletionToken &&completion_handler)
{
auto self = shared_from_this();
send_data = { asio::buffer(request.header()), asio::buffer(request.body()) };
connection->write_async(send_data, [self, &completion_handler](std::error_code error, std::size_t bytes_transfered) {
if (error) {
ESP_LOGE(TAG, "Request write error: %s", error.message().c_str());
return;
}
ESP_LOGD(TAG, "Bytes Transfered: %d", bytes_transfered);
self->get_response(completion_handler);
});
}
private:
template<class CompletionToken>
void get_response(CompletionToken &&completion_handler)
{
auto self = shared_from_this();
connection->read_async(asio::buffer(receive_buffer), [self, &completion_handler](std::error_code error, std::size_t bytes_received) {
if (error and error.value() != asio::error::eof) {
return;
}
ESP_LOGD(TAG, "Bytes Received: %d", bytes_received);
if (bytes_received == 0) {
return;
}
Response response(std::begin(self->receive_buffer), bytes_received);
completion_handler(self, response);
});
}
/*
* For this example we assumed 2048 to be enough for the receive_buffer
*/
std::array<char, 2048> receive_buffer;
/*
* The hardcoded 2 below is related to the type we receive the data to send. We gather the parts from Request, header
* and body, to send avoiding the copy.
*/
std::array<asio::const_buffer, 2> send_data;
std::shared_ptr<Connection> connection;
};
/** @brief Execute a fully async HTTP request
*
* @tparam completion_handler
* @param ctx io context
* @param request
*
* @note : We build this function as a simpler interface to compose the operations of connecting to
* the address and running the HTTP session. The Http::Session class is injected to the completion handler
* for further use.
*/
template<class CompletionToken>
void request_async(asio::io_context &context, const Request &request, CompletionToken &&completion_handler)
{
/*
* The first step is to resolve the address we want to connect to.
* The AddressResolution itself is injected to the completion handler.
*
* This shared_ptr is destroyed by the end of the scope. Pay attention that this is a non blocking function
* the lifetime of the object is extended by the resolve call
*/
std::make_shared<AddressResolution>(context)->resolve(request.host(), request.service_port(),
[&context, &request, completion_handler](std::shared_ptr<AddressResolution> resolver, tcp::resolver::results_type results) {
/* After resolution we create a Connection.
* The completion handler gets a shared_ptr<Connection> to receive the connection, once the
* connection process is complete.
*/
std::make_shared<Connection>(context)->start(results,
[&request, completion_handler](std::shared_ptr<Connection> connection) {
// Now we create a HTTP::Session and inject the necessary connection.
std::make_shared<Session>(connection)->send_request(request, completion_handler);
});
});
}
}// namespace Http
extern "C" void app_main(void)
{
// Basic initialization of ESP system
esp_init();
asio::io_context io_context;
Http::Request request(Http::Method::GET, "www.httpbin.org", "80", "/get");
Http::request_async(io_context, request, [](std::shared_ptr<Http::Session> session, Http::Response response) {
/*
* We only print the response here but could reuse session for other requests.
*/
response.print();
});
// io_context.run will block until all the tasks on the context are done.
io_context.run();
ESP_LOGI(TAG, "Context run done");
ESP_ERROR_CHECK(example_disconnect());
}