libevent-2.1.8-stable.tar.gz 下载
openssl-1.1.1a.tar.gz 下载

openssl 交叉编译在《arm-linux 交叉编译wget支持openssl, 使wget支持https链接地址下载文件》一文中已经有具体的编译安装说明了，在这里就不展开描述了;

[1]. 解压libevent-2.1.8-stable.tar.gz
    tar -zxvf libevent-2.1.8-stable.tar.gz
    
[2]. ./configure --prefix=/home/arm-libevent/ --host=arm-none-linux-gnueabi CC=arm-none-linux-gnueabi-gcc CXX=arm-none-linux-gnueabi-g++ 预配置libevent
    
[3]. 修改configure好生成的Makefile文件 查找OPENSSL_INCS和OPENSSL_LIBS修改内容如下
    OPENSSL_INCS = -I/home/openssl_install/include/
    OPENSSL_LIBADD = 
    OPENSSL_LIBS = -L/home/openssl_install/lib/ -lssl -lcrypto  
    其中/home/openssl_install/include/和/home/openssl_install/lib/是交叉编译的openssl安装路径
    
[4]. 由于Makefile中对于sample目录中的libevent例程中的交叉编译没有设置编译选项参数导出编译le-proxy.c        openssl_hostname_validation.c https-client.c 等文件提示找不到openssl/ssl.h 等相关头文件, 由于我们只需要交叉编译的libevent库和头文件，所以我将le-proxy.c openssl_hostname_validation.c https-client.c文件中的内容屏蔽了，不进行具体内容实现了，这样编译也就不抱错误，直接通过;
     
[5]. make 编译

[6]. make install 安装到prefix路径下面去了

[6]. 编写几个简单的demo测试一下

test.c

#include <stdio.h>
#include <sys/types.h>
#include <event.h>
#include <event2/event-config.h>

struct event ev;
struct timeval tv;

void time_cb(int fd, short event, void* argc)
{
	printf("timer wakeup. \r\n");
	event_add(&ev, &tv);
}

int main(int argc, char* argv[])
{
	struct event_base *base = event_init();
	tv.tv_sec = 0;
	tv.tv_usec = 100*1000;
	evtimer_set(&ev, time_cb, NULL);
	event_base_set(base, &ev);
	event_add(&ev, &tv);
	event_base_dispatch(base);
	return 0;
}

交叉编译test.c: arm-none-linux-gnueabi-gcc test.c -o test_event -I/home/arm-libevent/include/ -L/home/arm-libevent/lib/ -levent

client.c

#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<errno.h>
#include<unistd.h>
 
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
 
#include<event.h>
#include<event2/util.h>
 
int tcp_connect_server(const char* server_ip, int port);
 
void cmd_msg_cb(int fd, short events, void* arg);
void socket_read_cb(int fd, short events, void *arg);
 
int main(int argc, char** argv)
{
    if( argc < 3 )
    {
        printf("please input 2 parameter\n");
        return -1;
    }
 
 
    //两个参数依次是服务器端的IP地址、端口号
    int sockfd = tcp_connect_server(argv[1], atoi(argv[2]));
    if( sockfd == -1)
    {
        perror("tcp_connect error ");
        return -1;
    }
 
    printf("connect to server successful\n");
 
    struct event_base* base = event_base_new();
 
    struct event *ev_sockfd = event_new(base, sockfd,
                                        EV_READ | EV_PERSIST,
                                        socket_read_cb, NULL);
    event_add(ev_sockfd, NULL);
 
    //监听终端输入事件
    struct event* ev_cmd = event_new(base, STDIN_FILENO,
                                      EV_READ | EV_PERSIST, cmd_msg_cb,
                                      (void*)&sockfd);
 
    event_add(ev_cmd, NULL);
 
    event_base_dispatch(base);
 
    printf("finished \n");
    return 0;
}

void cmd_msg_cb(int fd, short events, void* arg)
{
    char msg[1024];
 
    int ret = read(fd, msg, sizeof(msg));
    if( ret <= 0 )
    {
        perror("read fail ");
        exit(1);
    }
 
    int sockfd = *((int*)arg);
 
    //把终端的消息发送给服务器端
    //为了简单起见，不考虑写一半数据的情况
    write(sockfd, msg, ret);
}

void socket_read_cb(int fd, short events, void *arg)
{
    char msg[1024];
 
    //为了简单起见，不考虑读一半数据的情况
    int len = read(fd, msg, sizeof(msg)-1);
    if( len <= 0 )
    {
        perror("read fail ");
        exit(1);
    }
 
    msg[len] = '\0';
 
    printf("recv %s from server\n", msg);
}
 
typedef struct sockaddr SA;
int tcp_connect_server(const char* server_ip, int port)
{
    int sockfd, status, save_errno;
    struct sockaddr_in server_addr;
 
    memset(&server_addr, 0, sizeof(server_addr) );
 
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port);
    status = inet_aton(server_ip, &server_addr.sin_addr);
 
    if( status == 0 ) //the server_ip is not valid value
    {
        errno = EINVAL;
        return -1;
    }
 
    sockfd = socket(PF_INET, SOCK_STREAM, 0);
    if( sockfd == -1 )
        return sockfd;
 
 
    status = connect(sockfd, (SA*)&server_addr, sizeof(server_addr) );
 
    if( status == -1 )
    {
        save_errno = errno;
        close(sockfd);
        errno = save_errno; //the close may be error
        return -1;
    }
 
    evutil_make_socket_nonblocking(sockfd);
 
    return sockfd;
}

交叉编译client.c: arm-none-linux-gnueabi-gcc client.c -o client -I/home/arm-libevent/include/ -L/home/arm-libevent/lib/ -levent 

server.c

#include<stdio.h>
#include<string.h>
#include<errno.h>
 
#include<unistd.h>
#include<event.h>
 
void accept_cb(int fd, short events, void* arg);
void socket_read_cb(int fd, short events, void *arg);
 
int tcp_server_init(int port, int listen_num);
 
int main(int argc, char** argv)
{
 
    int listener = tcp_server_init(9999, 10);
    if( listener == -1 )
    {
        perror(" tcp_server_init error ");
        return -1;
    }
 
    struct event_base* base = event_base_new();
 
    //添加监听客户端请求连接事件
    struct event* ev_listen = event_new(base, listener, EV_READ | EV_PERSIST,
                                        accept_cb, base);
    event_add(ev_listen, NULL);
 
 
    event_base_dispatch(base);
 
    return 0;
}
 
 
 
void accept_cb(int fd, short events, void* arg)
{
    evutil_socket_t sockfd;
 
    struct sockaddr_in client;
    socklen_t len = sizeof(client);
 
    sockfd = accept(fd, (struct sockaddr*)&client, &len );
    evutil_make_socket_nonblocking(sockfd);
 
    printf("accept a client %d\n", sockfd);
 
    struct event_base* base = (struct event_base*)arg;
 
    //仅仅是为了动态创建一个event结构体
    struct event *ev = event_new(NULL, -1, 0, NULL, NULL);
    //将动态创建的结构体作为event的回调参数
    event_assign(ev, base, sockfd, EV_READ | EV_PERSIST,
                 socket_read_cb, (void*)ev);
 
    event_add(ev, NULL);
}
 
 
void socket_read_cb(int fd, short events, void *arg)
{
    char msg[4096];
    struct event *ev = (struct event*)arg;
    int len = read(fd, msg, sizeof(msg) - 1);
 
 
 
    if( len <= 0 )
    {
        printf("some error happen when read\n");
        event_free(ev);
        close(fd);
        return ;
    }
 
    msg[len] = '\0';
    printf("recv the client msg: %s", msg);
 
    char reply_msg[4096] = "I have recvieced the msg: ";
    strcat(reply_msg + strlen(reply_msg), msg);
 
    write(fd, reply_msg, strlen(reply_msg) );
}
 
 
 
typedef struct sockaddr SA;
int tcp_server_init(int port, int listen_num)
{
    int errno_save;
    evutil_socket_t listener;
 
    listener = socket(AF_INET, SOCK_STREAM, 0);
    if( listener == -1 )
        return -1;
 
    //允许多次绑定同一个地址。要用在socket和bind之间
    evutil_make_listen_socket_reuseable(listener);
 
    struct sockaddr_in sin;
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = 0;
    sin.sin_port = htons(port);
 
    if(bind(listener, (SA*)&sin, sizeof(sin)) < 0 )
        goto error;
 
    if(listen(listener, listen_num) < 0)
        goto error;
 
 
    //跨平台统一接口，将套接字设置为非阻塞状态
    evutil_make_socket_nonblocking(listener);
 
    return listener;
 
    error:
        errno_save = errno;
        evutil_closesocket(listener);
        errno = errno_save;
 
        return -1;
}

在PC端编译server.c: gcc server.c -o server -I/usr/libevent/include/ -L/usr/libevent/lib/ -levent