libevent实现http server

libevent 是一个事件触发的网络库，适用于 windows、linux、bsd 、Android 等多种平台，内部使用 select、epoll、kqueue 、完成端口等系统调用管理事件机制。著名分布式缓存软件 memcached 也是 libevent based 。

最近在学习 libevent ，之前基于 libevent 实现了一个 http client ，没有用到 bufferevent 。这次实现了一个 http server ，很简单，只支持 GET 方法，不支持 Range 请求，但完全自己实现，是一个完整可用的示例。这里使用 libevent-2.1.3-alpha 。

我关于 libevent 的其它文章，列在这里供参考：

libevent实现http client
libevent实现echoclient
libevent http client
libevent 在 Android 上的一个改进

使用 libevent 实现一个 http server ，有这么几个步骤：

监听
启动事件循环
接受连接
解析 http 请求
回应客户端

关于监听， libevent 提供了 evconnlistener ，使用起来非常简单，通过一些设置，调用 evconnlistener_new_bind 即可完成一个服务端 socket 的创建，可以参考官方文档Connection Listeners 。下面是启动 server 的代码：

int start_http_server(struct event_base *evbase)
{int bind_times = 0;struct sockaddr_in sin;memset(&sin, 0, sizeof(sin));sin.sin_family = AF_INET;
#ifdef WIN32sin.sin_addr.S_un.S_addr = inet_addr(g_host);
#elsesin.sin_addr.s_addr = inet_addr(g_host);
#endifsin.sin_port = htons(g_port);trybind:g_listener = evconnlistener_new_bind(evbase, _accept_connection, 0,LEV_OPT_CLOSE_ON_FREE|LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_EXEC|LEV_OPT_DEFERRED_ACCEPT, -1,(struct sockaddr*)&sin, sizeof(sin));if (!g_listener){if(bind_times++ >=3){printf("couldn\'t create listener\n");return 1;}else{sin.sin_port = 0;goto trybind;}}else if(bind_times > 0){socklen_t len = sizeof(sin);getsockname(evconnlistener_get_fd(g_listener),(struct sockaddr*)&sin, &len);g_port = ntohs(sin.sin_port);}evconnlistener_set_error_cb(g_listener, _accept_error_cb);return 0;
}

关于事件循环，event_base_new 可以创建一个 event_base 实例， event_base_loop 可以进入事件循环。下面是 main() 函数中关于事件循环的代码：

    g_evbase = event_base_new();if( 0 == start_http_server(g_evbase) ){event_base_loop(g_evbase, EVLOOP_NO_EXIT_ON_EMPTY);printf("httpserver exit now.\n");}else{printf("httpserver, start server failed\n");}event_base_free(g_evbase);

上面的代码中，启动事件循环时传递了一个标志 EVLOOP_NO_EXIT_ON_EMPTY ，对于服务器程序，这是必须的，否则在没有待处理事件时，事件循环会立即退出。

通过给 evconnlistener 设置一些回调，就可以接受连接、处理错误。下面是相关代码：

static void _accept_connection(struct evconnlistener *listener,evutil_socket_t fd, struct sockaddr *addr, int socklen, void * ctx)
{char address[64];struct http_connection *conn;struct sockaddr_in sin;short port = 0;/* get address and port*/memcpy(&sin, addr, sizeof(sin));sprintf(address, "%s", inet_ntoa(sin.sin_addr));port = ntohs(sin.sin_port);
#ifdef HTTP_SERVER_DEBUGprintf("httpserver, accept one connection from %s:%d\n", address, port);
#endifconn = new_http_connection(evconnlistener_get_base(listener),fd,address,port);
}static void _accept_error_cb(struct evconnlistener *listener, void *ctx)
{int err = EVUTIL_SOCKET_ERROR();printf("httpserver, got an error %d (%s) on the listener.\n", err, evutil_socket_error_to_string(err));
}

在创建调用 evconnlistener_new_bind 时我们传入了 _accept_connection 函数，当有连接进来时，_accept_connection 调用 new_http_connection 函数来处理。错误处理回调 _accept_error_cb 是通过 evconnlistener_set_error_cb 设置的，在上面的错误处理回调函数中，我们仅仅是输出了一条日志。

解析 http 请求，这里还是使用《使用http_parser解析URL》一文中提到的http_parser 。先看下 new_http_connection 函数的实现：

struct http_connection * new_http_connection(struct event_base *evbase,evutil_socket_t fd,char *address, int port)
{struct http_connection * conn = (struct http_connection*)malloc(sizeof(struct http_connection));conn->evbase = evbase;conn->fd = fd;conn->peer_address = strdup(address);conn->peer_port = port;conn->tv_timeout.tv_sec = 10;conn->tv_timeout.tv_usec = 0;conn->bev = bufferevent_socket_new(evbase, fd, BEV_OPT_CLOSE_ON_FREE);bufferevent_setcb(conn->bev, _read_callback, _write_callback, _event_callback, conn);bufferevent_enable(conn->bev, EV_READ|EV_TIMEOUT);bufferevent_set_timeouts(conn->bev, &conn->tv_timeout, &conn->tv_timeout);conn->parser_settings.on_message_begin = onHttpMessageBegin;conn->parser_settings.on_url = onHttpUrl;conn->parser_settings.on_header_field = onHttpHeaderField;conn->parser_settings.on_header_value = onHttpHeaderValue;conn->parser_settings.on_headers_complete = onHttpHeadersComplete;conn->parser_settings.on_body = onHttpBody;conn->parser_settings.on_message_complete = onHttpMessageComplete;conn->cur_header_tag = 0;conn->cur_tag_cap = 0;conn->cur_tag_size = 0;conn->cur_header_value = 0;conn->cur_value_cap = 0;conn->cur_value_size = 0;conn->header_tags = 0;conn->header_size = 0;conn->header_capacity = 0;conn->header_values = 0;conn->fp = 0;conn->data_size = 0;conn->remain = 0;conn->method = 0;conn->path = 0;conn->query_string = 0;conn->status_code = 0;conn->parser.data = conn;http_parser_init(&conn->parser, HTTP_REQUEST);return conn;
}

上面的代码根据传入的 socket 描述符和 event_base 完成了传入连接的配置工作。主要有几部分：

创建 bufferevent
设置读写回调
配置 http_parser_setting ，主要是一些回调函数，http_parser 分析数据后酌情调用
初始化 http_parser，调用 http_parser_init，注意传入类型是 HTTP_REQUEST

上面代码中的结构体 struct http_connection 保存了一个连接相关的所有数据，其定义如下：

struct http_connection {struct http_parser parser;struct http_parser_settings parser_settings;char *cur_header_tag;int cur_tag_cap;int cur_tag_size;char *cur_header_value;int cur_value_cap;int cur_value_size;char buffer[BUFFER_SIZE];struct event_base *evbase;evutil_socket_t fd;struct bufferevent *bev;struct timeval tv_timeout;char *peer_address;int peer_port;int state;unsigned write_enabled:1;unsigned user_stop:1;/* request info */const char * method;char * path;char * query_string;char version[4];char **header_tags;char **header_values;int header_capacity;int header_size;/* response info */FILE *fp;long remain;int data_size;int status_code;
};

需要说明的是，这里只是个示例， http 请求、响应、连接处理全部放在了一起，看起来比较方面。

关于 http 头部、数据解析， http_parser 会为我们做好一切，我们只要保存即可。

关于 http 响应，需要我们自己构建状态行、必要的头部信息（如 Content-Length ）。

所有这些，请参考文后的代码。

回应客户端的这里使用 bufferevent socket 。 libevent 抽象了一种缓冲机制，来给大多数应用场景提供方便，关于 bufferevents ，请参考官方文档（http://www.wangafu.net/~nickm/libevent-book/Ref6_bufferevent.html）。

使用 bufferevent socket 处理连接非常简单，只需要设置读写回调即可，这在上面已经提到，不再赘述。

到这里为止，关于一个 http server 的所有事情就说完了。下面是 http_connection.c 的所有代码（ new_http_connection 函数的代码在前面），可以正常运行。为使代码比较清晰，这里关于错误、封装、解耦等都简化处理了。

#define HTTP_HEADER_BEGIN        0x1
#define HTTP_HEADER_COMPLETE     0x2
#define HTTP_MESSAGE_BEGIN       0x4
#define HTTP_MESSAGE_COMPLETE    0x8#define STATUS_CODE(code, str) case code: return str;static const char * _status_string(int code)
{switch(code){STATUS_CODE(100, "Continue")STATUS_CODE(101, "Switching Protocols")STATUS_CODE(102, "Processing")                 // RFC 2518) obsoleted by RFC 4918STATUS_CODE(200, "OK")STATUS_CODE(201, "Created")STATUS_CODE(202, "Accepted")STATUS_CODE(203, "Non-Authoritative Information")STATUS_CODE(204, "No Content")STATUS_CODE(205, "Reset Content")STATUS_CODE(206, "Partial Content")STATUS_CODE(207, "Multi-Status")               // RFC 4918STATUS_CODE(300, "Multiple Choices")STATUS_CODE(301, "Moved Permanently")STATUS_CODE(302, "Moved Temporarily")STATUS_CODE(303, "See Other")STATUS_CODE(304, "Not Modified")STATUS_CODE(305, "Use Proxy")STATUS_CODE(307, "Temporary Redirect")STATUS_CODE(400, "Bad Request")STATUS_CODE(401, "Unauthorized")STATUS_CODE(402, "Payment Required")STATUS_CODE(403, "Forbidden")STATUS_CODE(404, "Not Found")STATUS_CODE(405, "Method Not Allowed")STATUS_CODE(406, "Not Acceptable")STATUS_CODE(407, "Proxy Authentication Required")STATUS_CODE(408, "Request Time-out")STATUS_CODE(409, "Conflict")STATUS_CODE(410, "Gone")STATUS_CODE(411, "Length Required")STATUS_CODE(412, "Precondition Failed")STATUS_CODE(413, "Request Entity Too Large")STATUS_CODE(414, "Request-URI Too Large")STATUS_CODE(415, "Unsupported Media Type")STATUS_CODE(416, "Requested Range Not Satisfiable")STATUS_CODE(417, "Expectation Failed")STATUS_CODE(418, "I\"m a teapot")              // RFC 2324STATUS_CODE(422, "Unprocessable Entity")       // RFC 4918STATUS_CODE(423, "Locked")                     // RFC 4918STATUS_CODE(424, "Failed Dependency")          // RFC 4918STATUS_CODE(425, "Unordered Collection")       // RFC 4918STATUS_CODE(426, "Upgrade Required")           // RFC 2817STATUS_CODE(500, "Internal Server Error")STATUS_CODE(501, "Not Implemented")STATUS_CODE(502, "Bad Gateway")STATUS_CODE(503, "Service Unavailable")STATUS_CODE(504, "Gateway Time-out")STATUS_CODE(505, "HTTP Version not supported")STATUS_CODE(506, "Variant Also Negotiates")    // RFC 2295STATUS_CODE(507, "Insufficient Storage")       // RFC 4918STATUS_CODE(509, "Bandwidth Limit Exceeded")STATUS_CODE(510, "Not Extended")                // RFC 2774}return 0;
}static void _prepare_response(struct http_connection *conn);
static void _disable_write(struct http_connection *conn);
static void _enable_write(struct http_connection *conn);
static void _close_socket(struct http_connection * conn);
static void _peacefull_close(struct http_connection * conn);
static void _send_response_header(struct http_connection *conn);/*
* http_parser callback
*/
static int onHttpMessageBegin(http_parser *parser)
{struct http_connection * conn = (struct http_connection *)parser->data;conn->state |= HTTP_MESSAGE_BEGIN;return 0;
}static int onHttpUrl(http_parser *parser, const char *at, size_t length)
{struct http_connection *conn = (struct http_connection *)parser->data;int i= 0;conn->path = (char*)malloc(length+1);strncpy(conn->path, at, length);conn->path[length] = 0;for(; i < length && at[i] != '?'; i++);if(i < length){/* got query string */i++;if(i < length){int qlen = length - i;conn->query_string = (char*)malloc(qlen + 1);strncpy(conn->query_string, at+i, qlen);conn->query_string[qlen] = 0;}}return 0;
}static inline void check_insert_header(http_parser *parser, struct http_connection *conn)
{/** insert the header we parsed previously* into the header map*/if( (conn->cur_header_tag && conn->cur_header_tag[0] != 0) &&(conn->cur_header_value && conn->cur_header_value[0] != 0)){if(!conn->header_tags ||conn->header_size == conn->header_capacity){conn->header_capacity += 8;conn->header_tags = (char**)realloc(conn->header_tags,sizeof(char*)*conn->header_capacity);conn->header_values = (char**)realloc(conn->header_tags, sizeof(char*)*conn->header_capacity);}conn->header_tags[conn->header_size] = conn->cur_header_tag;conn->header_values[conn->header_size++] = conn->cur_header_value;/**  clear header value. this sets up a nice* feedback loop where the next time* HeaderValue is called, it can simply append*/conn->cur_header_tag = 0;conn->cur_tag_cap = 0;conn->cur_tag_size = 0;conn->cur_header_value = 0;conn->cur_value_cap = 0;conn->cur_value_size = 0;}
}static void check_dynamic_string(char **str, int *cap, int size, int add_size)
{if(!*str || size + add_size >= *cap){*cap = size + add_size + 64;*str = (char*)realloc(*str, *cap);}
}static int onHttpHeaderField(http_parser *parser, const char *at, size_t length)
{struct http_connection * conn = (struct http_connection *)parser->data;check_insert_header(parser, conn);check_dynamic_string(&conn->cur_header_tag,&conn->cur_tag_cap, conn->cur_tag_size, length);strncpy(conn->cur_header_tag + conn->cur_tag_size, at, length);return 0;
}static int onHttpHeaderValue(http_parser *parser, const char *at, size_t length)
{struct http_connection * conn = (struct http_connection *)parser->data;check_dynamic_string(&conn->cur_header_value,&conn->cur_value_cap, conn->cur_value_size, length);strncpy(conn->cur_header_value + conn->cur_value_size, at, length);return 0;
}static int onHttpHeadersComplete(http_parser *parser)
{printf("server, http_connection, onHttpHeadersComplete\n");if(parser){struct http_connection * conn = (struct http_connection *)parser->data;if(conn){
#ifdef HTTP_SERVER_DEBUGint i = 0;
#endifcheck_insert_header(parser, conn);conn->state |= HTTP_HEADER_COMPLETE;conn->method = http_method_str((enum http_method)conn->parser.method);sprintf(conn->version, "%.1d.%.1d", conn->parser.http_major,conn->parser.http_minor);#ifdef HTTP_SERVER_DEBUGprintf("server,http_connection, %d headers\n", conn->header_size);for(; i < conn->header_size; i++){printf("header key %s value %s\n", conn->header_tags[i], conn->header_values[i]);}#endif}}return 0;
}static int onHttpBody(http_parser *parser, const char *at, size_t length)
{/* TODO: implement */return 0;
}static int onHttpMessageComplete(http_parser *parser)
{struct http_connection * conn = (struct http_connection *)parser->data;if(conn){_prepare_response(conn);;conn->state |= HTTP_MESSAGE_COMPLETE;_enable_write(conn);_send_response_header(conn);switch(conn->status_code){case 200:case 206:break;default:_disable_write(conn);_peacefull_close(conn);break;}}return 0;
}static void _prepare_response(struct http_connection *conn)
{char *filename = conn->path;char *p;int i = 0;if(strncmp(conn->method, "GET", 3) != 0){conn->status_code = 403;return;}while(*filename == '/') filename++;p = filename;while(*p != '?' && *p != 0) p++;if(*p == '?') *p = 0;conn->fp = fopen(filename, "rb");if(conn->fp){fseek(conn->fp, 0, SEEK_END);conn->remain = ftell(conn->fp);fseek(conn->fp, 0, SEEK_SET);conn->status_code = 200;printf("open %s OK\n", filename);}else{conn->status_code = 404;}
}static void _send_response_header(struct http_connection *conn)
{char * p = conn->buffer;p += sprintf(p, "HTTP/1.1 %d %s\r\n",conn->status_code,_status_string(conn->status_code));if(conn->status_code == 200){p += sprintf(p, "Content-Length: %d\r\n""Content-Type: application/octet-stream\r\n",conn->remain);}p += sprintf(p, "\r\n");//printf("response headers: %s\n", conn->buffer);bufferevent_write(conn->bev, conn->buffer, p - conn->buffer);
}static void _close_socket(struct http_connection * conn)
{if(conn && conn->fd != 0){if(conn->bev){bufferevent_free(conn->bev);conn->bev = 0;}evutil_closesocket(conn->fd);conn->fd = 0;}
}static void _peacefull_close(struct http_connection * conn)
{if( evbuffer_get_length(bufferevent_get_output(conn->bev)) == 0){printf("http_connection, all data sent, close connection(%s:%d)\n", conn->peer_address, conn->peer_port);/* delete this connection */delete_http_connection(conn);return;}else{printf("http_connection, wait bufferevent_socket to flush data\n");}
}static void _event_callback(struct bufferevent *bev, short what, void *ctx)
{struct http_connection * conn = (struct http_connection *)ctx;if( (what & (BEV_EVENT_READING | BEV_EVENT_TIMEOUT)) == (BEV_EVENT_READING | BEV_EVENT_TIMEOUT)){/* TODO: check socket alive */}else if((what &(BEV_EVENT_WRITING | BEV_EVENT_TIMEOUT)) == (BEV_EVENT_WRITING | BEV_EVENT_TIMEOUT)){/* TODO: check socket alive */}else if(what & BEV_EVENT_ERROR){/* TODO: error notify */printf( "http_connection, %s:%d, error - %s\n", conn->peer_address,conn->peer_port,evutil_socket_error_to_string( evutil_socket_geterror(conn->fd) ) );_close_socket(conn);}
}static void _disable_write(struct http_connection *conn)
{if(conn->write_enabled){bufferevent_disable(conn->bev, EV_WRITE|EV_TIMEOUT);conn->write_enabled = 0;}
}static void _enable_write(struct http_connection *conn)
{if(!conn->write_enabled){bufferevent_enable(conn->bev, EV_WRITE | EV_TIMEOUT);conn->write_enabled = 1;}
}// default write callback
static void _write_callback(struct bufferevent *bev, void * args)
{struct http_connection * conn = (struct http_connection *)args;if(conn->fp){if(feof(conn->fp)){printf("http_connection, call peacefull_close via EOF\n");_peacefull_close(conn);}else{int to_read = BUFFER_SIZE;if(to_read > conn->remain) to_read = conn->remain;conn->data_size = fread(conn->buffer, 1, to_read, conn->fp);conn->remain -= conn->data_size;
#ifdef HTTP_SERVER_DEBUGprintf("http_connection, read %d bytes\n", conn->data_size);
#endifif(conn->data_size)bufferevent_write(bev, conn->buffer, conn->data_size);}}else{printf("http_connection, call peacefull_close via fp NULL\n");_peacefull_close(conn);}
}// default read callback
static void _read_callback(struct bufferevent *bev, void * args)
{struct http_connection * conn = (struct http_connection *)args;int n;while( (n = bufferevent_read(bev, conn->buffer, BUFFER_SIZE)) > 0 ){http_parser_execute(&conn->parser, &conn->parser_settings, conn->buffer, n);}
}void delete_http_connection(struct http_connection *conn)
{int i = 0;_disable_write(conn);_close_socket(conn);/* free resources */if(conn->peer_address)free(conn->peer_address);if(conn->fp)fclose(conn->fp);if(conn->cur_header_tag)free(conn->cur_header_tag);if(conn->cur_header_value)free(conn->cur_header_value);if(conn->path)free(conn->path);if(conn->query_string)free(conn->query_string);for(; i < conn->header_size; i++){free(conn->header_tags[i]);free(conn->header_values[i]);}free(conn->header_tags);free(conn->header_values);free(conn);
}

libevent实现http server相关推荐

基于Libevent的HTTP Server
简单的Http Server 使用Libevent内置的http相关接口,可以很容易的构建一个Http Server,一个简单的Http Server如下: #include <event2/e ...
libevent和libcurl实现http和https服务器 cJSON使用
前言 libevent和libcurl都是功能强大的开源库:libevent主要实现服务器,包含了select.epoll等高并发的实现:libcurl实现了curl命令的API封装,主要作为客户端. ...
ott盒子 MySQL_Linux+Nginx+MySql+Php既LNMP源码安装
前言: 我们都知道Apache作为一款出色的web服务器占据了市场大半个江山,他的地位目前还无人能取代,但是除了Apache,,在web服务器软件行列,Nginx以其性能稳定.功能丰富.运维简单.处理 ...
基于libevent和unix domain socket的本地server
https://www.pacificsimplicity.ca/blog/libevent-echo-server-tutorial 根据这一篇写一个最简单的demo.然后开始写client. cl ...
libevent 实现的socket 通信 server以及解决找不到动态库的方法
注: client 个人觉得没必要用 libvent来实现就没写注:由于涉及到回调函数的使用如有疑惑的可以先去了解回调函数的实现机理先来说一下 libevent主要是干啥的 : 内部封装了 s ...
【slighttpd】基于lighttpd架构的Server项目实战(2)—预备知识之libevent
转载地址:https://blog.csdn.net/jiange_zh/article/details/50631393 简介由于本项目是纯异步的,而对于大量 socket 连接,使用 selec ...
libevent入门教程：Echo Server based on libevent - Blog of Felix021 - 日，泯然众人矣。
libevent入门教程:Echo Server based on libevent 转载请注明出自 http://www.felix021.com/blog/read.php?2068 ,如是转载文 ...
libevent介绍
libevent是一款事件驱动的网络开发包由于采用 c 语言开发体积小巧,跨平台,速度极快. 通常我们在建立服务器的处理模型的时候,主要是下面集中模型; (1) a new Connecti ...
Libevent实现TCP服务循环监听
目标建立一个简单的tcp服务,可持续的监听客户端的连接和请求细节 libevent stream socket EV_READ | EV_PERSIST 代码要义libevent对stream_ ...

libevent实现http server

libevent实现http server相关推荐

最新文章

热门文章