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icomet(https://github.com/ideawu/icomet) is HTTP a server-push comet solution, it supports all popular browsers and OSes, including Safari/iOS(iPhone, iPad, iPod), Safari/Mac, IE/Windows, Chrome, Firefox/Mac, Windows.

icomet is written in C++, built with libevent, and is totally open sourced.

Building a web chat with icomet is very easy, the provided JavaScript client library is easy to use:

var comet = new iComet({
    channel: 'abc',
    signUrl: 'http://127.0.0.1:8000/sign',
    subUrl: 'http://127.0.0.1:8100/sub',
    callback: function(msg){
        // on server push
        alert(msg.content);
    }
});

You can see the Live Demo here: http://www.ideawu.com/icomet/chat.html

Although we can set a close callback on HTTP connection, but the HTTP server is not notified if client close unexpetedly, such as CTRL+C.

 evhttp_connection_set_closecb(req->evcon, on_close, NULL);

Because libevent called bufferevent_disable(evon, EV_READ) to stop read on the connection, so the server would not know the client close by read() returns 0, or send() causes SIGPIPE.

All you need to is to re-enable EV_READ on that connection:

struct bufferevent *bev = evhttp_connection_get_bufferevent(req->evcon);
bufferevent_enable(bev, EV_READ);

This is a simple HTTP client written in C with libevent2, the client makes a HTTP request to a web server, and print out the response HTML text. Here’s the codes:

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <evhttp.h>
#include <event2/event.h>
#include <event2/http.h>
#include <event2/bufferevent.h>

void http_request_done(struct evhttp_request *req, void *arg){
    char buf[1024];
    int s = evbuffer_remove(req->input_buffer, &buf, sizeof(buf) - 1);
    buf[s] = '\0';
    printf("%s", buf);
    // terminate event_base_dispatch()
    event_base_loopbreak((struct event_base *)arg);
}

int main(int argc, char **argv){
    struct event_base *base;
    struct evhttp_connection *conn;
    struct evhttp_request *req;

    base = event_base_new();
    conn = evhttp_connection_base_new(base, NULL, "127.0.0.1", 8080);
    req = evhttp_request_new(http_request_done, base);

    evhttp_add_header(req->output_headers, "Host", "localhost");
    //evhttp_add_header(req->output_headers, "Connection", "close");

    evhttp_make_request(conn, req, EVHTTP_REQ_GET, "/index.php?id=1");
    evhttp_connection_set_timeout(req->evcon, 600);
    event_base_dispatch(base);

    return 0;
}