libevent(2) : 用libevent改写server端 实现echo_server

(1)  echo_server.c

listen_event的callback函数是 do_accept_cb

bev (buffer event)的三个callback函数：read_cb, write_cb, error_cb。 本例中，server端无需write_cb函数

#include <stdio.h>#include <stdlib.h>#include <strings.h>#include <errno.h>#include <assert.h>#include <event2/event.h>#include <event2/bufferevent.h>#define LISTEN_PORT 9999#define LISTEN_BACKLOG 32#define oops(msg) { perror(msg); exit(EXIT_FAILURE); }void read_cb(struct bufferevent *bev, void *arg) {#define MAX_LINE    256    char line[MAX_LINE+1];    int n;    evutil_socket_t fd = bufferevent_getfd(bev);    while (n = bufferevent_read(bev, line, MAX_LINE), n > 0) {        line[n] = '\0';        printf("fd=%u, read line: %s\n", fd, line);        bufferevent_write(bev, line, n);    }}void write_cb(struct bufferevent *bev, void *arg) {}void error_cb(struct bufferevent *bev, short event, void *arg) {    evutil_socket_t fd = bufferevent_getfd(bev);    printf("fd = %u, ", fd);    if (event & BEV_EVENT_TIMEOUT) {        printf("Timed out\n"); //if bufferevent_set_timeouts() called    }    else if (event & BEV_EVENT_EOF) {        printf("connection closed\n");    }    else if (event & BEV_EVENT_ERROR) {        printf("some other error\n");    }    bufferevent_free(bev);}void do_accept_cb(evutil_socket_t sockfd, short event_type, void *arg){evutil_socket_t fd;struct sockaddr_in sin;socklen_t slen;fd = accept(sockfd, (struct sockaddr *)&sin, &slen);if (fd < 0) oops("ERROR: accept: ");if (fd > FD_SETSIZE) oops("ERROR: fd > FD_SETSIZE");printf("ACCEPT: fd = %u\n", fd);struct event_base *base;base = (struct event_base *)arg;struct bufferevent *bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);bufferevent_setcb(bev, read_cb, NULL, error_cb, arg);bufferevent_enable(bev, EV_READ|EV_WRITE|EV_PERSIST);}int main(int argc, char **argv){evutil_socket_t socket_fd;socket_fd = socket(PF_INET, SOCK_STREAM, 0);assert(socket_fd > 0);if(socket_fd == -1) oops("ERROR: socket initiate:");evutil_make_listen_socket_reuseable(socket_fd);struct sockaddr_in address;bzero((void *)&address, sizeof(address));address.sin_family = AF_INET;address.sin_addr.s_addr = inet_addr("172.16.166.129");//address.sin_addr.s_addr = 0;address.sin_port =  htons(LISTEN_PORT);int bind_return =  bind(socket_fd, (struct sockaddr *)&address, sizeof(address));if(bind_return == -1) oops("ERROR: bind:");int listen_return = listen(socket_fd, LISTEN_BACKLOG);if(listen_return == -1) oops("ERROR: listen:");//================================================puts("Listening...");    evutil_make_socket_nonblocking(socket_fd);    struct event_base *base;    struct event *listen_event;    base = event_base_new();    assert(base != NULL);    if(base == NULL) oops("ERROR: event_base_new() :");    listen_event = event_new(base, socket_fd, EV_READ|EV_PERSIST, do_accept_cb, (void*)base);    event_add(listen_event, NULL); //NULL: no timeout    event_base_dispatch(base);    puts("The End.");return 0;}

(2) echo_client.c 

一个普通的client端，没有用libevent.

改进方法：可以设置buffer_event, 然后实现write_cb函数和error_cb函数。

#include<stdio.h>#include<stdlib.h>#include<string.h>#include<unistd.h>#include<sys/types.h>#include<sys/socket.h>#include<netinet/in.h>#include <arpa/inet.h>#define oops(msg) { perror(msg); exit(EXIT_FAILURE); }#define SIZE 256#define LISTEN_PORT 9999int main(){        int socket_fd = socket(PF_INET, SOCK_STREAM, 0);        if(socket_fd == -1) oops("socket initiating error...");        struct sockaddr_in address;        bzero(&address, sizeof(address));        address.sin_family = AF_INET;        address.sin_addr.s_addr = inet_addr("172.16.166.129");//        address.sin_addr.s_addr = 0;        address.sin_port =  htons(LISTEN_PORT);        int connect_result = connect(socket_fd, (struct sockaddr*)&address, sizeof(address));        if(connect_result == -1) oops("connect error...");        char buffer[] = "hello world";        ssize_t write_length = write(socket_fd, buffer, strlen(buffer)+1); //write to socket_fdif(write_length != (strlen(buffer)+1)) oops("error: write ...");        ssize_t read_length = read(socket_fd, buffer, strlen(buffer)+1);        if(read_length == -1) oops("error: read data from socket...");        printf("the ret msg is: %s\n", buffer);        close(socket_fd);        return EXIT_SUCCESS;}

3. Makefile.am

AM_CPPFLAGS = -I/usr/local/include

LDADD = -L/usr/local/lib -levent

bin_PROGRAMS = echo-server echo-client

echo_server_SOURCES = echo_server.c

echo_client_SOURCES = echo_client.c