unix/linux 系统实现多个进程监听同一个端口

爱被打了一巴掌 2022-09-30 09:45 272阅读 0赞

转自：http://blog.csdn.net/youjun9007228198/article/details/19946129

一直疑惑一个应用app如何才能以多进程，多线程的方式运行。对于多线程可能很好理解，我们只要在进程中启用多线程的模式即可。也就是来一个请求，我们就用函数pthread\_create（）启用一个线程即可。这样我们的应用就可以在单进程，多线程的模式下工作。

但我们知道一个应用app通常工作在多进程，多线程的模式下，它的效率是最高的。那么我们如何才能做到多进程模式呢？经验告诉我们，如果多次启动一个进程会报错：“Address already in use!"。这是由于bind函数导致的，由于该端口号已经被监听了。

其实我们只要在绑定端口号（bind函数）之后，监听端口号之前（listen函数），用fork（）函数生成子进程，这样子进程就可以克隆父进程，达到监听同一个端口的目的。好了，废话不多说，我们看一下具体代码。

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    <div style="border-left-width:1px; border-left-style:solid; border-left-color:rgb(222,226,227); overflow-x:auto; overflow-y:hidden"> 
     <pre style="word-wrap:normal; color:rgb(51,51,51); border:none; font-family:Menlo,'Liberation Mono',Consolas,'Courier New','andale mono','lucida console',monospace; margin-top:0px; margin-bottom:0px; padding:10px 0px; line-height:16px!important; background-color:rgb(255,255,255)">
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#include&lt;stdio.h&gt;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#include&lt;stdlib.h&gt;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#include&lt;sys/types.h&gt;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#include&lt;sys/socket.h&gt;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#include&lt;netinet/in.h&gt;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#include&lt;unistd.h&gt;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">

</div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#define oops(m) {perror(m); exit(1);}</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(68,85,136); font-weight:bold">int</span>	
            
             
       <span style="color:rgb(153,0,0); font-weight:bold">main</span>
            
             
       <span>(){ </span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span style="color:rgb(68,85,136); font-weight:bold">int</span>	
            
             
       <span>sock_id</span>
            
             
       <span>;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">struct</span>	
            
             
       <span>sockaddr_in</span>	
            
             
       <span>saddr</span>
            
             
       <span>;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span>sock_id</span> 
            
             
       <span>=</span> 
            
             
       <span>socket</span>
            
             
       <span>(</span>
            
             
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       <span>SOCK_STREAM</span>
            
             
       <span>,</span> 
            
             
       <span style="color:rgb(0,153,153)">0</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span>saddr</span>
            
             
       <span>.</span>
            
             
       <span>sin_addr</span>
            
             
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       <span>s_addr</span> 
            
             
       <span>=</span> 
            
             
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       <span style="color:rgb(221,34,0); background-color:rgb(255,240,240)">"127.0.0.1"</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span>saddr</span>
            
             
       <span>.</span>
            
             
       <span>sin_port</span> 	      
            
             
       <span>=</span> 
            
             
       <span>htons</span>
            
             
       <span>(</span>
            
             
       <span style="color:rgb(0,153,153)">9988</span>
            
             
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      <div style="padding:0px 10px">	
            
             
       <span>saddr</span>
            
             
       <span>.</span>
            
             
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       <span>AF_INET</span>
            
             
       <span>;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span style="color:rgb(68,85,136); font-weight:bold">int</span> 
            
             
       <span>ret</span> 
            
             
       <span>=</span> 
            
             
       <span>bind</span>
            
             
       <span>(</span>
            
             
       <span>sock_id</span>
            
             
       <span>,</span> 
            
             
       <span>(</span>
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">struct</span> 
            
             
       <span>sockaddr</span> 
            
             
       <span>*</span>
            
             
       <span>)</span> 
            
             
       <span>&amp;</span>
            
             
       <span>saddr</span>
            
             
       <span>,</span> 
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">sizeof</span>
            
             
       <span>(</span>
            
             
       <span>saddr</span>
            
             
       <span>));</span>
            
             
       <span style="color:rgb(136,136,136)">//绑定IP地址和端口</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">if</span>
            
             
       <span>(</span>
            
             
       <span>ret</span> 
            
             
       <span>==</span> 
            
             
       <span>-</span>
            
             
       <span style="color:rgb(0,153,153)">1</span>
            
             
       <span>)</span> 
            
             
       <span>oops</span>
            
             
       <span>(</span>
            
             
       <span style="color:rgb(221,34,0); background-color:rgb(255,240,240)">"bind error"</span>
            
             
       <span>);</span>
            
             
       <span style="color:rgb(136,136,136)">//如果返回-1，则绑定失败，一般为“Address alreay in use”</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span style="color:rgb(68,85,136); font-weight:bold">int</span>	
            
             
       <span>i</span>
            
             
       <span>;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">for</span>
            
             
       <span>(</span>
            
             
       <span>i</span> 
            
             
       <span>=</span> 
            
             
       <span style="color:rgb(0,153,153)">0</span>
            
             
       <span>;</span> 
            
             
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       <span>;</span> 
            
             
       <span>i</span>
            
             
       <span>++</span>
            
             
       <span>){ </span>
            
             
       <span style="color:rgb(136,136,136)">//连续创建六个子进程</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span style="color:rgb(68,85,136); font-weight:bold">int</span> 
            
             
       <span>pid</span> 
            
             
       <span>=</span> 
            
             
       <span>fork</span>
            
             
       <span>();</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">if</span>
            
             
       <span>(</span>
            
             
       <span>pid</span> 
            
             
       <span>==</span> 
            
             
       <span style="color:rgb(0,153,153)">0</span>
            
             
       <span>)</span> 
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">break</span>
            
             
       <span>;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span>}</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span>listen</span>
            
             
       <span>(</span>
            
             
       <span>sock_id</span>
            
             
       <span>,</span> 
            
             
       <span style="color:rgb(0,153,153)">1</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">while</span>
            
             
       <span>(</span>
            
             
       <span style="color:rgb(0,153,153)">1</span>
            
             
       <span>){ </span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span style="color:rgb(68,85,136); font-weight:bold">int</span>	
            
             
       <span>sock</span> 
            
             
       <span>=</span> 
            
             
       <span>accept</span>
            
             
       <span>(</span>
            
             
       <span>sock_id</span>
            
             
       <span>,</span> 
            
             
       <span style="color:rgb(0,134,179)">NULL</span>
            
             
       <span>,</span> 
            
             
       <span style="color:rgb(0,153,153)">0</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span style="color:rgb(68,85,136); font-weight:bold">char</span> 	
            
             
       <span>buf</span>
            
             
       <span>[</span>
            
             
       <span style="color:rgb(0,153,153)">128</span>
            
             
       <span>];</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span style="color:rgb(68,85,136); font-weight:bold">int</span>	
            
             
       <span>readnum</span>
            
             
       <span>;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span>readnum</span> 
            
             
       <span>=</span> 
            
             
       <span>read</span>
            
             
       <span>(</span>
            
             
       <span>sock</span>
            
             
       <span>,</span> 
            
             
       <span>buf</span>
            
             
       <span>,</span> 
            
             
       <span style="color:rgb(0,153,153)">127</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span>buf</span>
            
             
       <span>[</span>
            
             
       <span>readnum</span>
            
             
       <span>]</span> 
            
             
       <span>=</span> 
            
             
       <span style="color:rgb(221,17,68)">'\0'</span>
            
             
       <span>;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span>printf</span>
            
             
       <span>(</span>
            
             
       <span style="color:rgb(221,34,0); background-color:rgb(255,240,240)">"pid=%d, mesg: %s</span>
            
             
       <span style="color:rgb(221,17,68)">\n</span>
            
             
       <span style="color:rgb(221,34,0); background-color:rgb(255,240,240)">"</span>
            
             
       <span>,</span> 
            
             
       <span>getpid</span>
            
             
       <span>(),</span> 
            
             
       <span>buf</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span>fflush</span>
            
             
       <span>(</span>
            
             
       <span>stdout</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span>close</span>
            
             
       <span>(</span>
            
             
       <span>sock</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span>}</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">return</span> 
            
             
       <span style="color:rgb(0,153,153)">1</span>
            
             
       <span>;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span>}</span>
           
            
      </div></pre> 
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##### [ 来自CODE的代码片][CODE]  serv.c #####

接下来我们来启动一下，查看结果如下：

F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD  
4 S   500  3019  2370  0  80   0 -  1315 -      tty2     00:00:01 bash  
0 S   500  7332  3019  0  80   0 -   466 -      tty2     00:00:00 multi\_proc  
1 S   500  7333  7332  0  80   0 -   466 -      tty2     00:00:00 multi\_proc  
1 S   500  7334  7332  0  80   0 -   466 -      tty2     00:00:00 multi\_proc  
1 S   500  7335  7332  0  80   0 -   466 -      tty2     00:00:00 multi\_proc  
1 S   500  7336  7332  0  80   0 -   466 -      tty2     00:00:00 multi\_proc  
1 S   500  7337  7332  0  80   0 -   466 -      tty2     00:00:00 multi\_proc  
1 S   500  7338  7332  0  80   0 -   466 -      tty2     00:00:00 multi\_proc

我们可以看到，确实有多个服务（multi\_proc)成功起来了，那么这些进程是否能够监听9988这个端口，并且产生竞争呢？我们来写一段客户端的代码做个[测试][Link 1]。客户端主要是循环多次请求服务器，并发送字符串。

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   <td style="border:none; margin:0px; padding:0px; vertical-align:top"> 
    <div style="border-left-width:1px; border-left-style:solid; border-left-color:rgb(222,226,227); overflow-x:auto; overflow-y:hidden"> 
     <pre style="word-wrap:normal; color:rgb(51,51,51); border:none; font-family:Menlo,'Liberation Mono',Consolas,'Courier New','andale mono','lucida console',monospace; margin-top:0px; margin-bottom:0px; padding:10px 0px; line-height:16px!important; background-color:rgb(255,255,255)">
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#include&lt;stdio.h&gt;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#include&lt;stdlib.h&gt;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#include&lt;sys/types.h&gt;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#include&lt;sys/socket.h&gt;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#include&lt;unistd.h&gt;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(204,0,0); font-weight:bold">#include&lt;netinet/in.h&gt;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">

</div>
           
            
      <div style="padding:0px 10px">
            
             
       <span style="color:rgb(68,85,136); font-weight:bold">int</span>	
            
             
       <span style="color:rgb(153,0,0); font-weight:bold">main</span>
            
             
       <span>(){ </span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span style="color:rgb(68,85,136); font-weight:bold">int</span>	
            
             
       <span>i</span>
            
             
       <span>=</span>
            
             
       <span style="color:rgb(0,153,153)">0</span>
            
             
       <span>;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">struct</span>	
            
             
       <span>sockaddr_in</span>	
            
             
       <span>saddr</span>
            
             
       <span>;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span>saddr</span>
            
             
       <span>.</span>
            
             
       <span>sin_addr</span>
            
             
       <span>.</span>
            
             
       <span>s_addr</span> 
            
             
       <span>=</span> 
            
             
       <span>inet_addr</span>
            
             
       <span>(</span>
            
             
       <span style="color:rgb(221,34,0); background-color:rgb(255,240,240)">"127.0.0.1"</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span>saddr</span>
            
             
       <span>.</span>
            
             
       <span>sin_port</span> 	      
            
             
       <span>=</span> 
            
             
       <span>htons</span>
            
             
       <span>(</span>
            
             
       <span style="color:rgb(0,153,153)">9988</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span>saddr</span>
            
             
       <span>.</span>
            
             
       <span>sin_family</span>      
            
             
       <span>=</span> 
            
             
       <span>AF_INET</span>
            
             
       <span>;</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span style="color:rgb(68,85,136); font-weight:bold">int</span>	
            
             
       <span>addlen</span> 	          
            
             
       <span>=</span> 
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">sizeof</span>
            
             
       <span>(</span>
            
             
       <span>saddr</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">for</span>
            
             
       <span>(;</span> 
            
             
       <span>i</span> 
            
             
       <span>&lt;</span> 
            
             
       <span style="color:rgb(0,153,153)">30</span>
            
             
       <span>;</span> 
            
             
       <span>i</span>
            
             
       <span>++</span>
            
             
       <span>){ </span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span style="color:rgb(68,85,136); font-weight:bold">int</span>	
            
             
       <span>sock</span>
            
             
       <span>=</span>
            
             
       <span>socket</span>
            
             
       <span>(</span>
            
             
       <span>AF_INET</span>
            
             
       <span>,</span> 
            
             
       <span>SOCK_STREAM</span>
            
             
       <span>,</span> 
            
             
       <span style="color:rgb(0,153,153)">0</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span>connect</span>
            
             
       <span>(</span>
            
             
       <span>sock</span>
            
             
       <span>,</span> 
            
             
       <span>(</span>
            
             
       <span style="color:rgb(0,0,0); font-weight:bold">struct</span> 
            
             
       <span>sockaddr</span> 
            
             
       <span>*</span>
            
             
       <span>)</span> 
            
             
       <span>&amp;</span>
            
             
       <span>saddr</span>
            
             
       <span>,</span> 
            
             
       <span>addlen</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">		
            
             
       <span>write</span>
            
             
       <span>(</span>
            
             
       <span>sock</span>
            
             
       <span>,</span> 
            
             
       <span style="color:rgb(221,34,0); background-color:rgb(255,240,240)">"Hello Server!"</span>
            
             
       <span>,</span> 
            
             
       <span style="color:rgb(0,153,153)">13</span>
            
             
       <span>);</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">	
            
             
       <span>}</span>
           
            
      </div>
           
            
      <div style="padding:0px 10px">
            
             
       <span>}</span>
           
            
      </div></pre> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

##### [ 来自CODE的代码片][CODE 1]  clnt.c #####

请求执行后，我们看一下，服务器打印的结果！

pid=7738, mesg: Hello Server!

pid=7736, mesg: Hello Server!

pid=7735, mesg: Hello Server!

pid=7734, mesg: Hello Server!

pid=7733, mesg: Hello Server!

pid=7737, mesg: Hello Server!

pid=7736, mesg: Hello Server!

pid=7735, mesg: Hello Server!

pid=7734, mesg: Hello Server!

pid=7732, mesg: Hello Server!