c语言 libevent库实现简易http server

短命女 2022-09-12 14:54 127阅读 0赞

# 一、使用libevent编写高并发HTTP server #

## libevent库使得高并发响应HTTP Server的编写变得很容易。整个过程包括如下几部：初始化，创建HTTP Server, 指定callback, 进入事件循环。另外在回调函数中，可以获取客户端请求(request的HTTP Header和参数等)，进行响应的处理，再将结果发送给客户端(response的HTTP Header和内容，如html代码)。libevent除了设置generic的callback，还可以对特定的请求路径设置对应的callback(回调/处理函数)。 ##

# 二、代码 #

连接库：-levent

#include <stdio.h>
        #include <stdlib.h>
        #include <unistd.h> //for getopt, fork
        #include <string.h> //for strcat
        #include <sys/queue.h>
        #include <event.h> / /for http
        #include <evhttp.h>
        #include <signal.h>
    
        #define MYHTTPD_SIGNATURE "myhttpd v 0.0.1"
    
        //处理模块
        void httpd_handler(struct evhttp_request *req, void *arg) { 
            char output[2048] = "\0";
            char tmp[1024];
    
            //获取客户端请求的URI(使用evhttp_request_uri或直接req->uri)
            const char *uri;
            uri = evhttp_request_uri(req);
            sprintf(tmp, "uri=%s\n", uri);
            strcat(output, tmp);
    
            sprintf(tmp, "uri=%s\n", req->uri);
            strcat(output, tmp);
            //decoded uri
            char *decoded_uri;
            decoded_uri = evhttp_decode_uri(uri);
            sprintf(tmp, "decoded_uri=%s\n", decoded_uri);
            strcat(output, tmp);
    
            //解析URI的参数(即GET方法的参数)
            struct evkeyvalq params;
            evhttp_parse_query(decoded_uri, &params);
            sprintf(tmp, "q=%s\n", evhttp_find_header(&params, "q"));
            strcat(output, tmp);
            sprintf(tmp, "s=%s\n", evhttp_find_header(&params, "s"));
            strcat(output, tmp);
            free(decoded_uri);
    
            //获取POST方法的数据
            char *post_data = (char *) EVBUFFER_DATA(req->input_buffer);
            sprintf(tmp, "post_data=%s\n", post_data);
            strcat(output, tmp);
    
            /* 具体的：可以根据GET/POST的参数执行相应操作，然后将结果输出 ... */
    
            /* 输出到客户端 */
    
            //HTTP header
            evhttp_add_header(req->output_headers, "Server", MYHTTPD_SIGNATURE);
            evhttp_add_header(req->output_headers, "Content-Type", "text/plain; charset=UTF-8");
            evhttp_add_header(req->output_headers, "Connection", "close");
            //输出的内容
            struct evbuffer *buf;
            buf = evbuffer_new();
            evbuffer_add_printf(buf, "It works!\n%s\n", output);
            evhttp_send_reply(req, HTTP_OK, "OK", buf);
            evbuffer_free(buf);
    
        }
        void show_help() { 
            char *help = "written by Min (http://54min.com)\n\n"
                "-l <ip_addr> interface to listen on, default is 0.0.0.0\n"
                "-p <num> port number to listen on, default is 1984\n"
                "-d run as a deamon\n"
                "-t <second> timeout for a http request, default is 120 seconds\n"
                "-h print this help and exit\n"
                "\n";
            fprintf(stderr, help);
        }
        //当向进程发出SIGTERM/SIGHUP/SIGINT/SIGQUIT的时候，终止event的事件侦听循环
        void signal_handler(int sig) { 
            switch (sig) { 
                case SIGTERM:
                case SIGHUP:
                case SIGQUIT:
                case SIGINT:
                    event_loopbreak();  //终止侦听event_dispatch()的事件侦听循环，执行之后的代码
                    break;
            }
        }
    
        int main(int argc, char *argv[]) { 
            //自定义信号处理函数
            signal(SIGHUP, signal_handler);
            signal(SIGTERM, signal_handler);
            signal(SIGINT, signal_handler);
            signal(SIGQUIT, signal_handler);
    
            //默认参数
            char *httpd_option_listen = "0.0.0.0";
            int httpd_option_port = 8080;
            int httpd_option_daemon = 0;
            int httpd_option_timeout = 120; //in seconds
    
            //获取参数
            int c;
            while ((c = getopt(argc, argv, "l:p:dt:h")) != -1) { 
                switch (c) { 
                case 'l' :
                    httpd_option_listen = optarg;
                    break;
                case 'p' :
                    httpd_option_port = atoi(optarg);
                    break;
                case 'd' :
                    httpd_option_daemon = 1;
                    break;
                case 't' :
                    httpd_option_timeout = atoi(optarg);
                     break;
                case 'h' :
                default :
                        show_help();
                        exit(EXIT_SUCCESS);
                }
            }
    
            //判断是否设置了-d，以daemon运行
            if (httpd_option_daemon) { 
                pid_t pid;
                pid = fork();
                if (pid < 0) { 
                    perror("fork failed");
                    exit(EXIT_FAILURE);
                }
                if (pid > 0) { 
                    //生成子进程成功，退出父进程
                    exit(EXIT_SUCCESS);
                }
            }
    
            /* 使用libevent创建HTTP Server */
    
            //初始化event API
            event_init();
    
            //创建一个http server
            struct evhttp *httpd;
            httpd = evhttp_start(httpd_option_listen, httpd_option_port);
            evhttp_set_timeout(httpd, httpd_option_timeout);
    
            //指定generic callback
            evhttp_set_gencb(httpd, httpd_handler, NULL);
            //也可以为特定的URI指定callback
            //evhttp_set_cb(httpd, "/", specific_handler, NULL);
    
            //循环处理events
            event_dispatch();
    
            evhttp_free(httpd);
            return 0;
        }