CentOS 7 使用异步网络框架Libevent

约定不等于承诺〃 2024-02-17 09:32 6阅读 0赞

## CentOS 7 安装Libevent库 ##

libevent github地址：[https://github.com/libevent/libevent][https_github.com_libevent_libevent]

步骤1：首先，你需要下载libevent的源代码。你可以从github或者源代码官方网站下载。并上传至/usr/local/source\_code/

![5cc63cc7978347949fa1205d4f2d9443.png][]

步骤2：下载完成后，需要将源代码解压，可以使用以下命令：

[root@localhost source_code]# tar -zxvf libevent-2.1.12-stable.tar.gz

步骤3：解压后，切换到源代码目录：

[root@localhost source_code]# cd libevent-2.1.12-stable

步骤4：生成cJSON动态/[静态库][Link 1]，执行如下指令：

[root@localhost libevent-2.1.12-stable]# ./configure
    checking for a BSD-compatible install... /usr/bin/install -c
    checking whether build environment is sane... yes
    checking for a thread-safe mkdir -p... /usr/bin/mkdir -p
    checking for gawk... gawk
    checking whether make sets $(MAKE)... yes
    checking whether make supports nested variables... yes
    checking whether make supports nested variables... (cached) yes
    checking whether make supports the include directive... yes (GNU
    ******
    [root@localhost libevent-2.1.12-stable]# make
      GEN      test/rpcgen-attempted
      GEN      include/event2/event-config.h
    make  all-am
    make[1]: 进入目录“/usr/local/source_code/libevent-2.1.12-stable”
      CC       sample/dns-example.o
      CC       buffer.lo
      CC       bufferevent.lo
      CC       bufferevent_filter.lo
    ******
    [root@localhost libevent-2.1.12-stable]# sudo make install
    make  install-am
    make[1]: 进入目录“/usr/local/source_code/libevent-2.1.12-stable”
    make[2]: 进入目录“/usr/local/source_code/libevent-2.1.12-stable”
     /usr/bin/mkdir -p '/usr/local/bin'
     /usr/bin/install -c event_rpcgen.py '/usr/local/bin'
     /usr/bin/mkdir -p '/usr/local/lib'
    ****

## 遇到的问题及解决办法 ##

编译执行./test\_libevent,提示如下截图错误信息：

![0470ae32256a467d9d9f470af89a6309.png][]

产生原因：在运行时，程序无法找到`libevent-2.1.so.7`这个动态库，因为该动态库在默认安装时，存放的路径在`/usr/local/lib`下，不在系统的默认查找路径内。

解决办法：

[root@localhost libevent_demo]# cat /etc/ld.so.conf
    include ld.so.conf.d/*.conf
    /usr/local/openssl/lib
    /usr/local/openssl/lib
    [root@localhost libevent_demo]# echo "/usr/local/lib" >> /etc/ld.so.conf
    [root@localhost libevent_demo]# sudo ldconfig

## Libevent 之Hello World ##

在/usr/local/source\_code 新增 libevent\_demo目录并新增 test\_libevent.cpp文件，文件内容如下：

#include <event2/event.h>
    #include <iostream>
    #include <string>
    void timer_cb(evutil_socket_t fd, short what, void *arg)
    {
        auto str = static_cast<std::string *>(arg);
        std::cout << *str << std::endl;
    }
    int main()
    {
        std::string str = "Hello, World!";
        auto *base = event_base_new();
        struct timeval five_seconds = {1, 0};
        auto *ev = event_new(base, -1, EV_TIMEOUT, timer_cb, (void *)&str);
        event_add(ev, &five_seconds);
        event_base_dispatch(base);
        event_free(ev);
        event_base_free(base);
        return 0;
    }

编译源码并执行：

[root@localhost libevent_demo]# g++ test_libevent.cpp -o test_libevent -levent
    [root@localhost libevent_demo]# ./test_libevent
    Hello, World!

## Libevent 参考资料： ##

libevent GitHub地址:[https://github.com/libevent/libevent][https_github.com_libevent_libevent]

libevent 编程指南: [https://senlinzhan.github.io/2017/08/12/libevent/][https_senlinzhan.github.io_2017_08_12_libevent]

libevent 深入浅出:[https://aceld.gitbooks.io/libevent/content/][https_aceld.gitbooks.io_libevent_content]

[https_github.com_libevent_libevent]: https://github.com/libevent/libevent
[5cc63cc7978347949fa1205d4f2d9443.png]: https://img-blog.csdnimg.cn/5cc63cc7978347949fa1205d4f2d9443.png
[Link 1]: https://so.csdn.net/so/search?q=%E9%9D%99%E6%80%81%E5%BA%93&spm=1001.2101.3001.7020
[0470ae32256a467d9d9f470af89a6309.png]: https://img-blog.csdnimg.cn/0470ae32256a467d9d9f470af89a6309.png
[https_senlinzhan.github.io_2017_08_12_libevent]: https://senlinzhan.github.io/2017/08/12/libevent/
[https_aceld.gitbooks.io_libevent_content]: https://aceld.gitbooks.io/libevent/content/