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c_socket.io_server筆記之長輪詢超時(timeout)處理

不吐不快

當你習慣了現有WEB服務器，諸如nginx、apache，JAVA應用服務器Tomcat等，你就不能不注意HTTP請求的響應超時時間，需要小心，尤其是反向代理時。當你可以自由控制請求timeout超時時，那是怎樣一個快意。
在libev中使用timeout，沒有像java那樣封裝的完善，一切都很原始，但確實鋒利多了。

長輪詢

一般長輪詢需要定義超時時間，一旦超時，服務器端會主動斷開連接。無論是xhr形式的長輪詢，還是jsonp長輪詢，在服務器端處理沒有多大差別，輸出數據有異。

輸出頭部

一般優先輸出頭部，告訴瀏覽器，需要保持長連接，當然，這需要瀏覽器支持http 1.1協議，并且明確的注明當前連接為一直保持著：keep-alive：

char heaer_str[200] = "";
strcat(heaer_str, "HTTP/1.1 200 OK\r\n");
strcat(heaer_str, "Content-Type: text/plain; charset=UTF-8\r\n");
strcat(heaer_str, "Connection: keep-alive\r\n");
strcat(heaer_str, "\r\n");
write_msg(client, heaer_str);

定時器啟動，等待

連接什么時候關閉，需要在代碼中手動控制，除非瀏覽器端在發出請求等待響應期間出現異常，無故斷開了連接。設服務器端設定好連接持續時間為30秒，那么就應該啟動一個定時器，除非所使用的語言層面提供了內置支持。

client->timeout.data = client;
ev_timer_init(&client->timeout, timeout_cb, 30.0, 0); //30s
ev_timer_start(loop, &client->timeout);

定時器start之后，觸發的函數timeout_cb：

1     static void timeout_cb(EV_P_ struct ev_timer *timer, int revents) {
2         if (EV_ERROR & revents) {
3             fprintf(stderr, "error event in timer_beat\n");
4             return ;
5         }
6
7         if (timer == NULL) {
8             fprintf(stderr, "the timer is NULL now !\n");
9             return;
10         }
11
12         client_t *client = timer->data;
13
14         if (client == NULL) {
15             fprintf(stderr, "Timeout the client is NULL !\n");
16             return;
17         }
18
19         write_msg(client, HTML_RESPONSE_ECHO);
20         free_res(loop, client);
21     }

可以看到，定時器觸發之后，本例中將輸出一串預先定義好的文字，然后關閉連接。
如何關閉觸發器，則很簡單：

    ev_timer *timer = &client->timeout;
    if (timer != NULL && (timer->data != NULL)) {
        ev_timer_stop(loop, timer);
    }

編譯運行

編譯一下：

gcc longpolling.c -o longpolling ../include/libev.a ../include/http-parser/http_parser.o -lm

運行它：

./long_polling

然后測試：

curl -i http://192.168.190.150:9000/long_polling

可以先看到頭部：

HTTP/1.1 200 OK Content-Type: text/plain; charset=UTF-8 Connection: keep-alive

等到30秒后輸出具體的文字內容：

The timeout(30s) had passed, you are welcome ~!

小結

所演示的長輪詢，沒有什么難度，HTTP 1.1頭部輸出，定時器啟動，然后等待輸出。
libev內含的timer組件簡單易用，控制方便，但不算是最佳實踐，官方文檔給出了若干種最佳實踐方式。具體可參閱:
http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#codeevtimercoderelativeandopti

完整代碼

	#include <arpa/inet.h>
	#include <stdlib.h>
	#include <stdio.h>
	#include <string.h>
	#include <fcntl.h>
	#include <err.h>

	#include "../include/ev.h"
	#include "../include/http-parser/http_parser.h"

	#define HTML_RESPONSE_ECHO "The timeout(30s) had passed, you are welcome ~!\r\n"
	#define SERVER_PORT 9000

	typedef struct {
	int fd;
	ev_timer timeout;
	ev_io ev_read;
	http_parser parser;
	} client_t;

	http_parser_settings settings;
	struct ev_loop *loop;
	ev_io ev_accept;

	static void free_res(struct ev_loop loop, client_t client);

	int setnonblock(int fd) {
	int flags = fcntl(fd, F_GETFL);
	if (flags < 0)
	return flags;

	flags \|= O_NONBLOCK;
	if (fcntl(fd, F_SETFL, flags) < 0)
	return -1;

	return 0;
	}

	static void write_msg(client_t client, char msg) {
	if (client == NULL) {
	fprintf(stderr, "the client is NULL !\n");
	return;
	}
	write(client->fd, msg, strlen(msg));
	}

	static void timeout_cb(EV_P_ struct ev_timer *timer, int revents) {
	if (EV_ERROR & revents) {
	fprintf(stderr, "error event in timer_beat\n");
	return ;
	}

	if (timer == NULL) {
	fprintf(stderr, "the timer is NULL now !\n");
	return;
	}

	client_t *client = timer->data;

	if (client == NULL) {
	fprintf(stderr, "Timeout the client is NULL !\n");
	return;
	}

	write_msg(client, HTML_RESPONSE_ECHO);
	free_res(loop, client);
	}

	static void read_cb(struct ev_loop loop, ev_io w, int revents) {
	client_t *client = w->data;
	int len = 0;
	char rbuff[1024];
	if (revents & EV_READ) {
	len = read(client->fd, &rbuff, 1024);
	}

	if (EV_ERROR & revents) {
	fprintf(stderr, "error event in read\n");
	free_res(loop, client);
	return ;
	}

	if (len < 0) {
	fprintf(stderr, "read error\n");
	ev_io_stop(EV_A_ w);
	free_res(loop, client);
	return;
	}

	if (len == 0) {
	fprintf(stderr, "client disconnected.\n");
	ev_io_stop(EV_A_ w);
	free_res(loop, client);
	return;
	}

	rbuff[len] = '\0';
	http_parser_init(&client->parser, HTTP_REQUEST);

	size_t parsed = http_parser_execute(&client->parser, &settings, rbuff, len);
	if (parsed < len) {
	fprintf(stderr, "parse error\n");
	ev_io_stop(EV_A_ w);
	free_res(loop, client);
	}
	}

	static void accept_cb(struct ev_loop loop, ev_io w, int revents) {
	struct sockaddr_in client_addr;
	socklen_t client_len = sizeof(client_addr);
	int client_fd = accept(w->fd, (struct sockaddr *) &client_addr, &client_len);
	if (client_fd == -1) {
	fprintf(stderr, "the client_fd is NULL !\n");
	return;
	}

	client_t *client = malloc(sizeof(client_t));
	client->fd = client_fd;
	if (setnonblock(client->fd) < 0)
	err(1, "failed to set client socket to non-blocking");

	client->ev_read.data = client;
	client->timeout.data = NULL;
	client->parser.data = client;

	ev_io_init(&client->ev_read, read_cb, client->fd, EV_READ);
	ev_io_start(loop, &client->ev_read);
	}

	int on_url_cb(http_parser parser, const char at, size_t length) {
	client_t *client = parser->data;

	char heaer_str[200] = "";
	strcat(heaer_str, "HTTP/1.1 200 OK\r\n");
	strcat(heaer_str, "Content-Type: text/plain; charset=UTF-8\r\n");
	strcat(heaer_str, "Connection: keep-alive\r\n");
	strcat(heaer_str, "\r\n");

	write_msg(client, heaer_str);

	client->timeout.data = client;
	ev_timer_init(&client->timeout, timeout_cb, 30.0, 0); //30s
	ev_timer_start(loop, &client->timeout);

	return 0;
	}

	int main(int argc, char const *argv[]) {
	loop = ev_default_loop(0);

	settings.on_url = on_url_cb;

	struct sockaddr_in listen_addr;
	int reuseaddr_on = 1;
	int listen_fd = socket(AF_INET, SOCK_STREAM, 0);
	if (listen_fd < 0)
	err(1, "listen failed");
	if (setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR, &reuseaddr_on, sizeof(reuseaddr_on)) == -1)
	err(1, "setsockopt failed");

	memset(&listen_addr, 0, sizeof(listen_addr));
	listen_addr.sin_family = AF_INET;
	listen_addr.sin_addr.s_addr = INADDR_ANY;
	listen_addr.sin_port = htons(SERVER_PORT);

	if (bind(listen_fd, (struct sockaddr *) &listen_addr, sizeof(listen_addr)) < 0)
	err(1, "bind failed");
	if (listen(listen_fd, 5) < 0)
	err(1, "listen failed");
	if (setnonblock(listen_fd) < 0)
	err(1, "failed to set server socket to non-blocking");

	ev_io_init(&ev_accept, accept_cb, listen_fd, EV_READ);
	ev_io_start(loop, &ev_accept);
	ev_loop(loop, 0);

	return 0;
	}

	static void free_res(struct ev_loop loop, client_t client) {
	if (client == NULL) {
	fprintf(stderr, "the client is NULL !!!!!!");
	return;
	}

	ev_io_stop(loop, &client->ev_read);

	ev_timer *timer = &client->timeout;
	if (timer != NULL && (timer->data != NULL)) {
	ev_timer_stop(loop, timer);
	}

	close(client->fd);

	free(client);
	}

view raw long_polling.c hosted with ❤ by GitHub

posted on 2013-03-27 08:57 nieyong 閱讀(4142) 評論(0) 編輯收藏所屬分類: socket.io

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c_socket.io_server筆記之長輪詢超時(timeout)處理

不吐不快

長輪詢

輸出頭部

定時器啟動，等待

編譯運行

小結

完整代碼

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聶永的博客

c_socket.io_server筆記之長輪詢超時(timeout)處理

不吐不快

長輪詢

輸出頭部

定時器啟動，等待

編譯運行

小結

完整代碼

公告

導航

統計

常用鏈接

留言簿(58)

隨筆分類(130)

隨筆檔案(151)

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定時器啟動，等待