5.1 創建和釋放evconnlistener
struct evconnlistener *evconnlistener_new_bind(struct event_base *base, evconnlistener_cb cb, void *ptr, unsigned flags, int backlog, const struct sockaddr *sa, int socklen); void evconnlistener_free(struct evconnlistener *lev);
兩個evconnlistener_new_bind()函數分配和返回一個新的連接監聽器對象。連接監聽器使用event_base來得知什麼時候在給定的監聽套接字上有新的TCP連接。新連接到達時,監聽器調用你給出的回調函數。
兩個函數中,base參數都是監聽器用於監聽連接的event_base。cb是收到新連接時要調用的回調函數;如果cb爲NULL,則監聽器是禁用的,直到設置了回調函數爲止。ptr指針將傳遞給回調函數。flags參數控制回調函數的行爲,下面會更詳細論述。backlog是任何時刻網絡棧允許處於還未接受狀態的最大未決連接數。如果backlog是負的,libevent會試圖挑選一個較好的值;如果爲0,libevent認爲已經對提供的套接字調用了listen()。
兩個函數的不同在於如何建立監聽套接字。evconnlistener_new()函數假定已經將套接字綁定到要監聽的端口,然後通過fd傳入這個套接字。如果要libevent分配和綁定套接字,可以調用evconnlistener_new_bind(),傳輸要綁定到的地址和地址長度。
可以給evconnlistener_new()函數的flags參數傳入一些標誌。可以用或(OR)運算任意連接下述標誌:
LEV_OPT_LEAVE_SOCKETS_BLOCKING /*默認情況下,連接監聽器接收新套接字後,會將其設置爲非阻塞的, 以便將其用於libevent。如果不想要這種行爲,可以設置這個標誌。*/ LEV_OPT_CLOSE_ON_FREE /*如果設置了這個選項,釋放連接監聽器會關閉底層套接字。*/ LEV_OPT_CLOSE_ON_EXEC /*如果設置了這個選項,連接監聽器會爲底層套接字設置close-on-exec標誌。*/ LEV_OPT_REUSEABLE /*設置這個標誌會讓libevent標記套接字是可重用的,這樣一旦關閉, 可以立即打開其他套接字,在相同端口進行監聽。*/ LEV_OPT_THREADSAFE /*爲監聽器分配鎖,這樣就可以在多個線程中安全地使用了。*/
連接監聽器回調函數:
typedef void (*evconnlistener_cb)(struct evconnlistener *listener, evutil_socket_t sock, struct sockaddr *addr, int len, void *ptr)
接收到新連接會調用提供的回調函數。listener參數是接收連接的連接監聽器。sock參數是新接收的套接字。addr和len參數是接收連接的地址和地址長度。ptr是調用evconnlistener_new()時用戶提供的指針。
要釋放連接監聽器,調用evconnlistener_free()。
5.2 啓用和禁用evconnlistener
int evconnlistener_disable(struct evconnlistener *lev); int evconnlistener_enable(struct evconnlistener *lev);
這兩個函數暫時禁止或者重新允許監聽新連接。
5.3 調整evconnlistener的回調函數
void evconnlistener_set_cb(struct evconnlistener *lev, evconnlistener_cb cb, void *arg);
函數調整evconnlistener的回調函數和其參數。
5.4 獲取event_base
struct event_base *evconnlistener_get_base(struct evconnlistener *lev);
5.5示例代碼
服務器端:tcp_server.c
/************************************************************************* # File Name: tcp_server.c # Author: wenong # mail: [email protected] # Created Time: 2016年09月03日 星期六 21時51分08秒 ************************************************************************/ static struct event_base * base; void write_buf_cb(struct bufferevent* bev, void* cbarg) { printf("%s\n", __FUNCTION__); } void read_buf_cb(struct bufferevent* bev, void* cbarg) { int ret, i; char buf[MAXBYTES]; ret = bufferevent_read(bev, buf, sizeof(buf)); printf("read_buf_cd length %d\n", ret); for(i = 0; i < ret; i++) { buf[i] = toupper(buf[i]); } bufferevent_write(bev, buf, ret); } void event_cb(struct bufferevent* bev, short event, void* cbarg) { if(BEV_EVENT_READING & event) puts("BEV_EVENT_READING"); if(BEV_EVENT_WRITING & event) puts("BEV_EVENT_WRITING"); if(BEV_EVENT_ERROR & event) puts("BEV_EVENT_ERROR"); if(BEV_EVENT_EOF & event) { puts("BEV_EVENT_EOF"); bufferevent_free(bev); } if(BEV_EVENT_TIMEOUT & event) { puts("BEV_EVENT_TIMEOUT"); bufferevent_free(bev); } } void accept_cb(struct evconnlistener *listener, evutil_socket_t clientfd, struct sockaddr *addr , int len, void *arg) { struct bufferevent* bev; struct event_base* base = (struct event_base*)arg; puts("Accept client connect"); evutil_make_socket_nonblocking(clientfd); bev = bufferevent_socket_new(base, clientfd, BEV_OPT_CLOSE_ON_FREE | BEV_OPT_DEFER_CALLBACKS); bufferevent_setcb(bev, (bufferevent_data_cb)read_buf_cb , (bufferevent_data_cb)write_buf_cb, (bufferevent_event_cb)event_cb, NULL); struct timeval timeout_read = {10, 0}; bufferevent_set_timeouts(bev, &timeout_read, NULL); bufferevent_setwatermark(bev, EV_READ, 10, 0); bufferevent_setwatermark(bev, EV_WRITE, 10, 0); bufferevent_enable(bev, EV_READ | EV_WRITE); } void main_loop(struct sockaddr_in * addr) { struct evconnlistener *evcon; base = event_base_new(); evcon = evconnlistener_new_bind(base, (evconnlistener_cb)accept_cb , (void*)base, LEV_OPT_CLOSE_ON_FREE | LEV_OPT_REUSEABLE , 128, (struct sockaddr*)addr, sizeof(struct sockaddr_in)); puts("server begin listenning..."); event_base_dispatch(base); evconnlistener_free(evcon); event_base_free(base); } int main(int argc, char** argv) { int serverfd; socklen_t serveraddrlen; struct sockaddr_in serveraddr; serveraddr.sin_family = AF_INET; serveraddr.sin_port = htons(SERVERPORT); serveraddr.sin_addr.s_addr = htonl(INADDR_ANY); serverfd = socket(AF_INET, SOCK_STREAM, 0); serveraddrlen = sizeof(serveraddr); main_loop( &serveraddr); return 0; }
客戶端代碼:tcp_client.c
/************************************************************************* # File Name: tcp_client.c # Author: wenong # mail: [email protected] # Created Time: 2016年09月03日 星期六 22時10分11秒 ************************************************************************/ static struct sockaddr_in serveraddr; static struct event_base* base; static struct bufferevent* bev; void* cmd_msg_cb(evutil_socket_t stdinfd, short what, void* arg) { int ret; char buf[MAXBYTES]; ret = read(stdinfd, buf, sizeof(buf)); bufferevent_write(bev, buf, ret); } void read_buf_cb(struct bufferevent* bev, void* cbarg) { int ret; char buf[MAXBYTES]; ret = bufferevent_read(bev, buf, sizeof(buf)); write(STDOUT_FILENO, buf, ret); } void event_cb(struct bufferevent* bev, short event, void* cbarg) { if(BEV_EVENT_READING & event) puts("BEV_EVENT_READING"); if(BEV_EVENT_WRITING & event) puts("BEV_EVENT_WRITING"); if(BEV_EVENT_ERROR & event) printf("BEV_EVENT_ERROR %s\n", strerror(EVUTIL_SOCKET_ERROR())); //獲取錯誤信息 if(BEV_EVENT_CONNECTED & event) puts("BEV_EVENT_CONNECTED"); if(BEV_EVENT_EOF & event) { puts("BEV_EVENT_EOF"); event_base_loopexit(base, NULL); } if(BEV_EVENT_TIMEOUT & event) { puts("BEV_EVENT_TIMEOUT"); event_base_loopexit(base, NULL); } } void main_loop() { struct event*ev_stdin; base = event_base_new(); bev = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE | BEV_OPT_DEFER_CALLBACKS); bufferevent_setcb(bev, (bufferevent_data_cb)read_buf_cb , NULL, (bufferevent_event_cb)event_cb, NULL); bufferevent_socket_connect(bev, (struct sockaddr*)&serveraddr, sizeof(struct sockaddr_in)); struct timeval timeout_read; timeout_read.tv_sec = 10; timeout_read.tv_usec = 0; bufferevent_set_timeouts(bev, &timeout_read, NULL); bufferevent_enable(bev, EV_READ); ev_stdin = event_new(base, STDIN_FILENO, EV_READ | EV_PERSIST , (event_callback_fn)cmd_msg_cb, NULL); event_add(ev_stdin, NULL); event_base_dispatch(base); bufferevent_free(bev); event_free(ev_stdin); event_base_free(base); puts("exit now..."); } int main(int argc, char** argv) { serveraddr.sin_family = AF_INET; inet_pton(AF_INET, SERVERIP, &serveraddr.sin_addr.s_addr); serveraddr.sin_port = htons(SERVERPORT); main_loop(); return 0; }