【ZMQ】第一个C服务器

技术背景 ØMQ (也拼写作ZeroMQ,0MQ或ZMQ),号称号称是“史上最快的消息队列”,基于c语言开发。ZMQ(以下ZeroMQ简称ZMQ

技术背景

ØMQ (也拼写作ZeroMQ,0MQ或ZMQ),号称号称是“史上最快的消息队列”,基于c语言开发。ZMQ(以下ZeroMQ简称ZMQ)是一个简单好用的传输层,像框架一样的一个socket library,他使得Socket编程更加简单、简洁和性能更高。是一个消息处理队列库,可在多个线程、内核和主机盒之间弹性伸缩。

作为C开发人员有两个选择 CZMQlibzmq (低级zeromq库)。

在这里简单记录 CentOS 下从零安装ZMQ相关依赖、解决各种问题最终实现一个最简单的请求-应答服务器-客户端效果。

ZeroMQ 在 centos下的安装

1)下载ZeroMQ

执行命令:

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wget http://download.zeromq.org/zeromq-4.0.4.tar.gz

2)解压ZeroMQ

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$ tar zvxf zeromq-4.0.4.tar.gz
$ mv zeromq-4.0.4 zeromq
$ cd zeromq

3)安装依赖

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$ yum install libtool
$ ./autogen.sh

4)编译安装

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$ ./configure
......
checking for gcc... no
checking for cc... no
checking for cl.exe... no
configure: error: in `/home/chuser/zeromq':
configure: error: no acceptable C compiler found in $PATH
See `config.log' for more details

提示缺少C编译器,先安装GCC

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$ sudo yum install gcc

安装OK!再次执行

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$ ./configure
......
checking whether the C++ compiler works... no
configure: error: Unable to find a working C++ compiler

提示缺少C++编译器,先安装G++。

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$ sudo yum install gcc-c++ 

安装OK!再次执行

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$ ./configure
$ make
$ sudo make install

ZeroMQ安装成功!

libzmq 在 CentOS 下的安装

libzmq开源仓库: https://github.com/zeromq/libzmq

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# 对于 CentOS 8,请以根用户 root 运行下面命令:
cd /etc/yum.repos.d/
wget https://download.opensuse.org/repositories/network:messaging:zeromq:release-stable/CentOS_8/network:messaging:zeromq:release-stable.repo
yum install zeromq-devel

# 对于 CentOS 7,请以根用户 root 运行下面命令:
cd /etc/yum.repos.d/
wget https://download.opensuse.org/repositories/network:messaging:zeromq:release-stable/CentOS_7/network:messaging:zeromq:release-stable.repo
yum install zeromq-devel

# 对于 CentOS 6,请以根用户 root 运行下面命令:
cd /etc/yum.repos.d/
wget https://download.opensuse.org/repositories/network:messaging:zeromq:release-stable/CentOS_6/network:messaging:zeromq:release-stable.repo
yum install zeromq-devel

Demo

(来源:https://zeromq.org/languages/c/#libzmq)

Server:

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#include <zmq.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>

int main (void)
{
// Socket to talk to clients
void *context = zmq_ctx_new ();
void *responder = zmq_socket (context, ZMQ_REP);
int rc = zmq_bind (responder, "tcp://*:5555");
assert (rc == 0);

while (1) {
char buffer [10];
zmq_recv (responder, buffer, 10, 0);
printf ("Received Hello\n");
sleep (1); // Do some 'work'
zmq_send (responder, "World", 5, 0);
}
return 0;
}

Client:

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Copy
#include <zmq.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>

int main (void)
{
printf ("Connecting to hello world server…\n");
void *context = zmq_ctx_new ();
void *requester = zmq_socket (context, ZMQ_REQ);
zmq_connect (requester, "tcp://localhost:5555");

int request_nbr;
for (request_nbr = 0; request_nbr != 10; request_nbr++) {
char buffer [10];
printf ("Sending Hello %d…\n", request_nbr);
zmq_send (requester, "Hello", 5, 0);
zmq_recv (requester, buffer, 10, 0);
printf ("Received World %d\n", request_nbr);
}
zmq_close (requester);
zmq_ctx_destroy (context);
return 0;
}

将文件存入以libzmq_server.clibzmq_client.c命名的文件。

运行下列命令编译:

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gcc libzmq_server.c -o libzmq_server -lzmq
gcc libzmq_client.c -o libzmq_client -lzmq

若出现错误,请移步异常问题记录区寻找答案

分别在两个终端运行,若成功,效果如下:

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$ ./libzmq_server
Received Hello
Received Hello
Received Hello
Received Hello
Received Hello
Received Hello
Received Hello
Received Hello
Received Hello
Received Hello
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$ ./libzmq_client
Connecting to hello world server…
Sending Hello 0
Received World 0
Sending Hello 1
Received World 1
Sending Hello 2
Received World 2
Sending Hello 3
Received World 3
Sending Hello 4
Received World 4
Sending Hello 5
Received World 5
Sending Hello 6
Received World 6
Sending Hello 7
Received World 7
Sending Hello 8
Received World 8
Sending Hello 9
Received World 9

异常记录

undefined reference to `zmq_sendmsg’

解决方案: 编译时带上 -lzmq

例如:gcc -o hello hello.c -lzmq

error while loading shared libraries: libzmq.so.3

方法1:

找一下动态文件安装到哪里了:

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$ whereis libzmq.so.3

$ find / -name libzmq.so.3

/usr/local/lib 加到共享库配置文件 /etc/ld.so.conf 中,该方法一劳永逸,但是需要有操作权限

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# cat /etc/ld.so.conf
include ld.so.conf.d/*.conf
# echo "/usr/local/lib">>/etc/ld.so.conf
# ldconfig

再执行成功.

方法2:设置环境变量LD_LIBRARY_PATH,适合没有操作权限时使用

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# vi ~/.bash_profile 

编辑你当前用户的用户目录下的.bash_profile文件 在文件后面加上:

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export LD_LIBRARY_PATH=/usr/local/lib/:$LD_LIBRARY_PATH

保存并关闭文件

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# source ~/.bash_profile 

使该文件改动生效(每次登录该用户时也会自动加载该文件,使文件生效) 执行成功

C程序头文件引用问题

一直没有搞清楚头文件引用 “” 和 <> 的区别,今天偶然查到:

  • first:include<fileName.h> 引用系统头文件一般用<>。
  • second:include”fileName.h” 引用自己定义的头文件一般用” “。

区别是<>首先去系统中去找,” “则在自己当前文件夹找。

一般情况下系统头文件在 usr/include/中。

参考文献


【ZMQ】第一个C服务器
https://www.frytea.com/post/20200609004700.html
作者
Tianlun Song
发布于
2020年6月9日
更新于
2024年6月10日
许可协议