C++实现轻量级极简httpserver和httpclient

一般来说，C++的项目多是偏底层，不怎么需要跟http打交道，但有时候又需要在C++后端项目中加入一些简单 http接口，比如游戏运营服务器，金融交易监控服务等。

但是传统的实现方法比如采用libcurl，asio等较为重型的框架来做有没有必要，因此，这里采用mongoose这个库来实现基本的httpserver和httpclient功能，非常简单，包含一个h文件，一个cpp文件到工程中就行了，无需编译，无需链接库。

本文实现了一个project，将mongoose中提供的http相关api封装成了httpserver类和httpclient类，方便调用，目录结构如下：

├─common
    ├─mongoose.h
    └─mongoose.cpp
├─httpclient
    ├─http_client.h
    ├─http_client.cpp
    └─main.cpp
└─httpserver
    └─web
       └─index.html
    ├─http_server.h
    ├─http_server.cpp
    └─main.cpp

编译环境：win10，vs2015， C++11 （其实是跨平台的）

http服务器

http_server.h

#pragma once

#include <string>
#include <unordered_map>
#include <functional>
#include "../common/mongoose.h"

// 定义http返回callback
typedef void OnRspCallback(mg_connection *c, std::string);
// 定义http请求handler
using ReqHandler = std::function<bool (std::string, std::string, mg_connection *c, OnRspCallback)>;

class HttpServer
{
public:
	HttpServer() {}
	~HttpServer() {}
	void Init(const std::string &port); // 初始化设置
	bool Start(); // 启动httpserver
	bool Close(); // 关闭
	void AddHandler(const std::string &url, ReqHandler req_handler); // 注册事件处理函数
	void RemoveHandler(const std::string &url); // 移除时间处理函数
	static std::string s_web_dir; // 网页根目录 
	static mg_serve_http_opts s_server_option; // web服务器选项
	static std::unordered_map<std::string, ReqHandler> s_handler_map; // 回调函数映射表

private:
	// 静态事件响应函数
	static void OnHttpEvent(mg_connection *connection, int event_type, void *event_data);
	static void HandleEvent(mg_connection *connection, http_message *http_req);
	static void SendRsp(mg_connection *connection, std::string rsp);

	std::string m_port;    // 端口
	mg_mgr m_mgr;          // 连接管理器
};

http_server.cpp

#include <utility>
#include "http_server.h"

void HttpServer::Init(const std::string &port)
{
	m_port = port;
	s_server_option.enable_directory_listing = "yes";
	s_server_option.document_root = s_web_dir.c_str();
	// TODO：其他设置
}

bool HttpServer::Start()
{
	mg_mgr_init(&m_mgr, NULL);
	mg_connection *connection = mg_bind(&m_mgr, m_port.c_str(), OnHttpEvent);
	if (connection == NULL)
		return false;
	mg_set_protocol_http_websocket(connection);

	printf("starting http server at port: %s\n", m_port.c_str());
	// loop
	while (true)
		mg_mgr_poll(&m_mgr, 500); // ms

	return true;
}

void HttpServer::OnHttpEvent(mg_connection *connection, int event_type, void *event_data)
{
	http_message *http_req = (http_message *)event_data;
	switch (event_type)
	{
	case MG_EV_HTTP_REQUEST:
		HandleEvent(connection, http_req);
		break;
	default:
		break;
	}
}

static bool route_check(http_message *http_msg, char *route_prefix)
{
	if (mg_vcmp(&http_msg->uri, route_prefix) == 0)
		return true;
	else
		return false;

	// TODO: 还可以判断 GET, POST, PUT, DELTE等方法
	//mg_vcmp(&http_msg->method, "GET");
	//mg_vcmp(&http_msg->method, "POST");
	//mg_vcmp(&http_msg->method, "PUT");
	//mg_vcmp(&http_msg->method, "DELETE");
}

void HttpServer::AddHandler(const std::string &url, ReqHandler req_handler)
{
	if (s_handler_map.find(url) != s_handler_map.end())
		return;

	s_handler_map.insert(std::make_pair(url, req_handler));
}

void HttpServer::RemoveHandler(const std::string &url)
{
	auto it = s_handler_map.find(url);
	if (it != s_handler_map.end())
		s_handler_map.erase(it);
}

void HttpServer::SendRsp(mg_connection *connection, std::string rsp)
{
	// 必须先发送header
	mg_printf(connection, "%s", "HTTP/1.1 200 OK\r\nTransfer-Encoding: chunked\r\n\r\n");
	// 以json形式返回
	mg_printf_http_chunk(connection, "{ \"result\": %s }", rsp.c_str());
	// 发送空白字符快，结束当前响应
	mg_send_http_chunk(connection, "", 0);
}

void HttpServer::HandleEvent(mg_connection *connection, http_message *http_req)
{
	std::string req_str = std::string(http_req->message.p, http_req->message.len);
	printf("got request: %s\n", req_str.c_str());

	// 先过滤是否已注册的函数回调
	std::string url = std::string(http_req->uri.p, http_req->uri.len);
	std::string body = std::string(http_req->body.p, http_req->body.len);
	auto it = s_handler_map.find(url);
	if (it != s_handler_map.end())
	{
		ReqHandler handle_func = it->second;
		handle_func(url, body, connection, SendRsp);
	}

	// 其他请求
	if (route_check(http_req, "/")) // index page
		mg_serve_http(connection, http_req, s_server_option);
	else if (route_check(http_req, "/api/hello")) 
	{
		// 直接回传
		SendRsp(connection, "welcome to httpserver");
	}
	else if (route_check(http_req, "/api/sum"))
	{
		// 简单post请求，加法运算测试
		char n1[100], n2[100];
		double result;

		/* Get form variables */
		mg_get_http_var(&http_req->body, "n1", n1, sizeof(n1));
		mg_get_http_var(&http_req->body, "n2", n2, sizeof(n2));

		/* Compute the result and send it back as a JSON object */
		result = strtod(n1, NULL) + strtod(n2, NULL);
		SendRsp(connection, std::to_string(result));
	}
	else
	{
		mg_printf(
			connection,
			"%s",
			"HTTP/1.1 501 Not Implemented\r\n"
			"Content-Length: 0\r\n\r\n");
	}
}

bool HttpServer::Close()
{
	mg_mgr_free(&m_mgr);
	return true;
}

index.html

<!DOCTYPE html>
<html>
<head>
  <title>RESTful API demo</title>

<script src="//code.jquery.com/jquery-1.11.0.min.js"></script>
<script type="text/javascript">

    $(document).ready(function(){
     $("button").click(function(){
        $.get("/api/hello",function(data, status){
            console.log("get rsp: ", data);
            $('#result1').html(data);
        });
       });
    });

    $(document).on('keyup', '#n1, #n2', function() {
      $.ajax({
        url: '/api/sum',
        method: 'POST',
        dataType: 'json',
        data: { n1: $('#n1').val(), n2: $('#n2').val() },
        success: function(json) {
          console.log("post rsp: ", json);
          $('#result2').html(json.result);
        }
      });
    });

</script>
</head>
<body>
    <h1>c++ httpserver demo</h1>

    <p>
      front end request
    </p>

    <h2>GET</h2>
    <div>
        <button id="btn">get request</button>
    </div>
    <div>
     <label>Result1:</label> <span id="result1"> </span>
    </div>

    <h2>POST</h2>
    <div>
      <label>Number 1:</label> <input type="text" id="n1" />
    </div>
    <div>
      <label>Number 2:</label> <input type="text" id="n2" />
    </div>
    <div>
     <label>Result2:</label> <span id="result2"> </span>
    </div>

</body>
</html>

main.cpp

#include <iostream>
#include <memory>
#include "http_server.h"

// 初始化HttpServer静态类成员
mg_serve_http_opts HttpServer::s_server_option;
std::string HttpServer::s_web_dir = "./web";
std::unordered_map<std::string, ReqHandler> HttpServer::s_handler_map;

bool handle_fun1(std::string url, std::string body, mg_connection *c, OnRspCallback rsp_callback)
{
	// do sth
	std::cout << "handle fun1" << std::endl;
	std::cout << "url: " << url << std::endl;
	std::cout << "body: " << body << std::endl;

	rsp_callback(c, "rsp1");

	return true;
}

bool handle_fun2(std::string url, std::string body, mg_connection *c, OnRspCallback rsp_callback)
{
	// do sth
	std::cout << "handle fun2" << std::endl;
	std::cout << "url: " << url << std::endl;
	std::cout << "body: " << body << std::endl;

	rsp_callback(c, "rsp2");

	return true;
}

int main(int argc, char *argv[]) 
{
	std::string port = "7999";
	auto http_server = std::shared_ptr<HttpServer>(new HttpServer);
	http_server->Init(port);
	// add handler
	http_server->AddHandler("/api/fun1", handle_fun1);
	http_server->AddHandler("/api/fun2", handle_fun2);
	http_server->RemoveHandler("/api/fun3");
	// http_server->RemoveHandler("/api/fun3");
	http_server->Start();
	
	return 0;
}

• 服务器支持host静态页面资源，也支持rest api调用
• 需要手动设置loop polling的时间间隔
• 可以自定义静态页面根路径，注册和解注册自定义api函数回调
• 某些变量必须声明定义成全局或者静态变量

http客户端

http_client.h

#pragma once
#include <string>
#include <functional>
#include "../common/mongoose.h"

// 此处必须用function类，typedef再后面函数指针赋值无效
using ReqCallback = std::function<void (std::string)>;

class HttpClient
{
public:
	HttpClient() {}
	~HttpClient() {}

	static void SendReq(const std::string &url, ReqCallback req_callback);
	static void OnHttpEvent(mg_connection *connection, int event_type, void *event_data);
	static int s_exit_flag;
	static ReqCallback s_req_callback;
};

http_client.cpp

#include "http_client.h"

// 初始化client静态变量
int HttpClient::s_exit_flag = 0;
ReqCallback HttpClient::s_req_callback;

// 客户端的网络请求响应
void HttpClient::OnHttpEvent(mg_connection *connection, int event_type, void *event_data)
{
	http_message *hm = (struct http_message *)event_data;
	int connect_status;

	switch (event_type) 
	{
	case MG_EV_CONNECT:
		connect_status = *(int *)event_data;
		if (connect_status != 0) 
		{
			printf("Error connecting to server, error code: %d\n", connect_status);
			s_exit_flag = 1;
		}
		break;
	case MG_EV_HTTP_REPLY:
	{
		printf("Got reply:\n%.*s\n", (int)hm->body.len, hm->body.p);
		std::string rsp = std::string(hm->body.p, hm->body.len);
		connection->flags |= MG_F_SEND_AND_CLOSE;
		s_exit_flag = 1; // 每次收到请求后关闭本次连接，重置标记
        
		// 回调处理
		s_req_callback(rsp);
	}
		break;
	case MG_EV_CLOSE:
		if (s_exit_flag == 0) 
		{
			printf("Server closed connection\n");
			s_exit_flag = 1;
		};
		break;
	default:
		break;
	}
}


// 发送一次请求，并回调处理，然后关闭本次连接
void HttpClient::SendReq(const std::string &url, ReqCallback req_callback)
{
	// 给回调函数赋值
	s_req_callback = req_callback;
	mg_mgr mgr;
	mg_mgr_init(&mgr, NULL);
	auto connection = mg_connect_http(&mgr, OnHttpEvent, url.c_str(), NULL, NULL);
	mg_set_protocol_http_websocket(connection);

	printf("Send http request %s\n", url.c_str());

	// loop
	while (s_exit_flag == 0)
		mg_mgr_poll(&mgr, 500);

	mg_mgr_free(&mgr);
}

main.cpp

#include <iostream>
#include "http_client.h"

void handle_func(std::string rsp)
{
	// do sth according to rsp
	std::cout << "http rsp1: " << rsp << std::endl;
}

int main()
{
	// 拼完整url，带参数，暂时只写了GET请求
	std::string url1 = "http://127.0.0.1:7999/api/hello";
	HttpClient::SendReq(url1, handle_func);
	
	std::string url2 = "http://127.0.0.1:7999/api/fun2";
	HttpClient::SendReq(url2, [](std::string rsp) { 
		std::cout << "http rsp2: " << rsp << std::endl; 
	});

	system("pause");

	return 0;
}

• client每次请求都是一个独立的请求
  
• 请求函数中加入回调用于处理网络返回

测试

可以用浏览器、或者其他工具提交url，查看网络请求返回

GET

请求 

http://localhost:7999/api/hello

结果

{ "result": welcome to httpserver }

POST

请求

http://localhost:7999/api/sum?n1=20&n2=18

结果

{ "result": 38 }

源码

csdn：demo

github: demo