libevent http library - usage examples

Libevent comes with an http library, which can be used to easily implement an http server.

/*************************************************************************
 *   > File Name: http.c
 *   > Author: liuqianghua
 *   > Mail: [email protected]
 *   > Created Time: Wed 20 Sep 2017 07:17:48 AM CST
 ************************************************************************/
 
#include <signal.h>
#include <event2/event.h>
#include <event2/http.h>
#include <event2/buffer.h>
#include <event2/keyvalq_struct.h>
 
static void hello_request_cb(struct evhttp_request *req, void *arg);
static void version_cb (struct evhttp_request *req, void *arg);
 
int main(int argc, char **argv)
{
    struct event_base *base;
    struct evhttp *http;
    struct evhttp_bound_socket *handle;
 
    if (signal(SIGPIPE, SIG_IGN) == SIG_ERR)
        return (1);
 
    /* firstly, you should build a event_base looper */
    base = event_base_new();
    if (!base) {
        fprintf(stderr, "Couldn't create an event_base: exiting\n");
        return 1;
    }
 
    /* sencondly, Create a new evhttp object to handle requests. */
    http = evhttp_new(base);
    if (!http) {
        fprintf(stderr, "couldn't create evhttp. Exiting.\n");
        return 1;
    }
 
    /* 想想我们在nginx里面配的各种uri，就知道这是什么了，是的就是那个东西*/
    evhttp_set_cb(http, "/hello", hello_request_cb, NULL);
 
    /* We want to accept arbitrary requests, so we need to set a "generic"
     *   * cb.  We can also add callbacks for specific paths. */
    /* 这是一个兜底的回调，即上面的各种uri都未匹配的情况下，进入这个通用的匹配，
     * 就相当于nginx的404页面或者nginx version的页面的作用*/
    evhttp_set_gencb(http, version_cb, argv[1]);
 
    /* Now we tell the evhttp what port to listen on */
    handle = evhttp_bind_socket_with_handle(http, "0.0.0.0", 8090);
    if (!handle) {
        fprintf(stderr, "couldn't bind to port %d. Exiting.\n",
                (int)8090);
        return 1;
    }
 
    event_base_dispatch(base);
 
    return 0;
}
 
static void hello_request_cb(struct evhttp_request *req, void *arg)
{
    const char *cmdtype;
    struct evkeyvalq *headers;
    struct evkeyval *header;
    struct evbuffer *buf;
 
    switch (evhttp_request_get_command(req)) {
        case EVHTTP_REQ_GET: cmdtype = "GET"; break;
        case EVHTTP_REQ_POST: cmdtype = "POST"; break;
        case EVHTTP_REQ_HEAD: cmdtype = "HEAD"; break;
        case EVHTTP_REQ_PUT: cmdtype = "PUT"; break;
        case EVHTTP_REQ_DELETE: cmdtype = "DELETE"; break;
        case EVHTTP_REQ_OPTIONS: cmdtype = "OPTIONS"; break;
        case EVHTTP_REQ_TRACE: cmdtype = "TRACE"; break;
        case EVHTTP_REQ_CONNECT: cmdtype = "CONNECT"; break;
        case EVHTTP_REQ_PATCH: cmdtype = "PATCH"; break;
        default: cmdtype = "unknown"; break;
    }
 
    printf("Received a %s request for %s\nHeaders:\n",
            cmdtype, evhttp_request_get_uri(req));
    headers = evhttp_request_get_input_headers(req);
    for (header = headers->tqh_first; header;
            header = header->next.tqe_next) {
        printf("  %s: %s\n", header->key, header->value);
    }
 
    buf = evhttp_request_get_input_buffer(req);
    /* 读取报文实体的数据 */
    puts("Input data: <<<");
    while (evbuffer_get_length(buf)) {
        int n;
        char cbuf[128];
        n = evbuffer_remove(buf, cbuf, sizeof(buf)-1);
        if (n > 0)
            (void) fwrite(cbuf, 1, n, stdout);
    }
    /* 向报文实体输出数据 */
    puts(">>>");
 
    evhttp_send_reply(req, 200, "OK", NULL);
}
 
static void version_cb (struct evhttp_request *req, void *arg)
{
    fprintf (stderr, "what is my version \n");
    evhttp_send_reply(req, 200, "OK", NULL);
}

Compile gcc -g http.c -levent 
and run ./a.out 

Enter each in the browser 

http://192.168.47.131:8090/hello2

http://192.168.47.131:8090/hello

Get the following output:

what is my version 
Received a GET request for /hello
Headers:
  Host: 192.168.47.131:8090
  User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:55.0) Gecko/20100101 Firefox/55.0
  Accept: text/ html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
  Accept-Language: zh-CN,zh;q=0.8,en-US;q=0.5,en;q=0.3
  Accept-Encoding: gzip, deflate
  Connection: keep-alive
  Upgrade-Insecure-Requests: 1
Input data: <<<
>>>
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Original link: https://blog.csdn.net/rin_cherish/article/details/78045993