linux epoll机制详解
<div id="navCategory"><h5 class="catalogue">目录</h5><ul class="first_class_ul"><li><span>select()和poll() io多路复用模型</span>
</li><li>
epoll io多路复用模型实现机制</li><li>
epoll实现机制</li><li>
epoll的接口</li><li>
epoll的工作模式</li><li>
示例说明：</li><li>
示例</li><li>
<span><strong>总结</strong></span>
</li></ul></div><p>
在linux 没有实现epoll事件驱动机制之前，我们一般选择用select或者poll等io多路复用的方法来实现并发服务程序。在linux新的内核中，有了一种替换它的机制，就是epoll。</p>
<p class="maodian"></p><h2>
<span>select()和poll() io多路复用模型</span>
</h2>
<p>
<strong>select的缺点： </strong></p>
<p>
1.单个进程能够监视的文件描述符的数量存在最大限制，通常是1024，当然可以更改数量，但由于select采用轮询的方式扫描文件描述符，文件描述符数量越多，性能越差；(在linux内核头文件中，有这样的定义：#define __fd_setsize 1024)<br>
2.内核 / 用户空间内存拷贝问题，select需要复制大量的句柄数据结构，产生巨大的开销；<br>
3.select返回的是含有整个句柄的数组，应用程序需要遍历整个数组才能发现哪些句柄发生了事件；<br>
4.select的触发方式是水平触发，应用程序如果没有完成对一个已经就绪的文件描述符进行io操作，那么之后每次select调用还是会将这些文件描述符通知进程。</p>
<p>
相比select模型，poll使用链表保存文件描述符，因此没有了监视文件数量的限制，但其他三个缺点依然存在。</p>
<p>
假设我们的服务器需要支持100万的并发连接，则在__fd_setsize 为1024的情况下，则我们至少需要开辟1k个进程才能实现100万的并发连接。除了进程间上下文切换的时间消耗外，从内核/用户空间大量的无脑内存拷贝、数组轮询等，是系统难以承受的。因此，基于select模型的服务器程序，要达到10万级别的并发访问，是一个很难完成的任务。</p>
<p class="maodian"></p><h2>
epoll io多路复用模型实现机制</h2>
<p>
由于epoll的实现机制与select/poll机制完全不同，上面所说的 select的缺点在epoll上不复存在。</p>
<p>
设想一下如下场景：有100万个客户端同时与一个服务器进程保持着tcp连接。而每一时刻，通常只有几百上千个tcp连接是活跃的(事实上大部分场景都是这种情况)。如何实现这样的高并发？</p>
<p>
在select/poll时代，服务器进程每次都把这100万个连接告诉操作系统(从用户态复制句柄数据结构到内核态)，让操作系统内核去查询这些套接字上是否有事件发生，轮询完后，再将句柄数据复制到用户态，让服务器应用程序轮询处理已发生的网络事件，这一过程资源消耗较大，因此，select/poll一般只能处理几千的并发连接。</p>
<p>
epoll的设计和实现与select完全不同。epoll通过在linux内核中申请一个简易的文件系统(文件系统一般用什么数据结构实现？b+树)。把原先的select/poll调用分成了3个部分：</p>
<p>
1）调用epoll_create()建立一个epoll对象(在epoll文件系统中为这个句柄对象分配资源)</p>
<p>
2）调用epoll_ctl向epoll对象中添加这100万个连接的套接字</p>
<p>
3）调用epoll_wait收集发生的事件的连接</p>
<p>
如此一来，要实现上面说是的场景，只需要在进程启动时建立一个epoll对象，然后在需要的时候向这个epoll对象中添加或者删除连接。同时，epoll_wait的效率也非常高，因为调用epoll_wait时，并没有一股脑的向操作系统复制这100万个连接的句柄数据，内核也不需要去遍历全部的连接。</p>
<p class="maodian"></p><h2>
epoll实现机制</h2>
<p>
当某一进程调用epoll_create方法时，linux内核会创建一个eventpoll结构体，这个结构体中有两个成员与epoll的使用方式密切相关。eventpoll结构体如下所示：</p>
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<code class="cpp keyword bold">struct</code> <code class="cpp plain">eventpoll{</code>
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<code class="cpp spaces"> </code><code class="cpp plain">....</code>
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<code class="cpp spaces"> </code><code class="cpp comments">/*红黑树的根节点，这颗树中存储着所有添加到epoll中的需要监控的事件*/</code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">rb_root rbr;</code>
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<code class="cpp spaces"> </code><code class="cpp comments">/*双链表中则存放着将要通过epoll_wait返回给用户的满足条件的事件*/</code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">list_head rdlist;</code>
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<code class="cpp spaces"> </code><code class="cpp plain">....</code>
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<code class="cpp plain">};</code>
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<p>
每一个epoll对象都有一个独立的eventpoll结构体，用于存放通过epoll_ctl方法向epoll对象中添加进来的事件。这些事件都会挂载在红黑树中，如此，重复添加的事件就可以通过红黑树而高效的识别出来(红黑树的插入时间效率是lgn，其中n为树的高度)。</p>
<p>
而所有<strong>添加到epoll中的事件都会与设备(网卡)驱动程序建立回调关系，也就是说，当相应的事件发生时会调用这个回调方法</strong>。这个回调方法在内核中叫ep_poll_callback,它会将发生的事件添加到rdlist双链表中。</p>
<p>
在epoll中，对于每一个事件，都会建立一个epitem结构体，如下所示：</p>
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<code class="cpp keyword bold">struct</code> <code class="cpp plain">epitem{</code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">rb_node rbn;</code><code class="cpp comments">//红黑树节点</code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">list_head rdllink;</code><code class="cpp comments">//双向链表节点</code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">epoll_filefd ffd; </code><code class="cpp comments">//事件句柄信息</code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">eventpoll *ep; </code><code class="cpp comments">//指向其所属的eventpoll对象</code>
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<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">epoll_event event; </code><code class="cpp comments">//期待发生的事件类型</code>
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<code class="cpp plain">}</code>
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<p>
当调用epoll_wait检查是否有事件发生时，只需要检查eventpoll对象中的rdlist双链表中是否有epitem元素即可。如果rdlist不为空，则把发生的事件复制到用户态，同时将事件数量返回给用户。</p>
<p>
<img title="linux epoll机制详解" alt="linux epoll机制详解" id="theimg" src="https://zhuji.jb51.net/uploads/img/202305/86e85b7a49d135d5850b6988f2df9819.jpg"></p>
<p>
通过红黑树和双链表数据结构，并结合回调机制，造就了epoll的高效。</p>
<p class="maodian"></p><h2>
epoll的接口</h2>
<p>
<strong>1.epoll_create </strong></p>
<p>
创建epoll句柄<br>
函数声明：int epoll_create(int size)</p>
<p>
参数：size用来告诉内核这个监听的数目一共有多大。<br>
返回值：返回创建了的epoll句柄。<br>
当创建好epoll句柄后，它就是会占用一个fd值，在linux下如果查看/proc/进程id/fd/，是能够看到这个fd的，所以在使用完epoll后，必须调用close()关闭，否则可能导致fd被耗尽。</p>
<p>
<strong>2.epoll_ctl </strong></p>
<p>
将被监听的描述符添加到epoll句柄或从epool句柄中删除或者对监听事件进行修改。<br>
函数申明：int epoll_ctl(int epfd, int op, int fd, struct epoll_event*event);</p>
<p>
参数：<br>
epfd： epoll_create()的返回值<br>
op：表示要进行的操作，其值分别为：<br>
epoll_ctl_add： 注册新的fd到epfd中；<br>
epoll_ctl_mod： 修改已经注册的fd的监听事件；<br>
epoll_ctl_del： 从epfd中删除一个fd；<br>
fd：需要操作/监听的文件句柄<br>
event：是告诉内核需要监听什么事件，struct epoll_event如下：</p>
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<code class="cpp keyword bold">typedef</code> <code class="cpp keyword bold">union</code> <code class="cpp plain">epoll_data { </code>
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<code class="cpp keyword bold">void</code> <code class="cpp plain">*ptr; </code>
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<code class="cpp color1 bold">int</code> <code class="cpp plain">fd; </code>
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<code class="cpp plain">__uint32_t u32; </code>
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<code class="cpp plain">__uint64_t u64; </code>
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<code class="cpp plain">} epoll_data_t; </code>
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<code class="cpp keyword bold">struct</code> <code class="cpp plain">epoll_event { </code>
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<code class="cpp plain">__uint32_t events; </code><code class="cpp comments">/* epoll events */</code>
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<code class="cpp plain">epoll_data_t data; </code><code class="cpp comments">/* user data variable */</code>
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<code class="cpp plain">};</code>
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<p>
events可以是以下几个宏的集合：</p>
<p>
epollin：触发该事件，表示对应的文件描述符上有可读数据。(包括对端socket正常关闭)；<br>
epollout：触发该事件，表示对应的文件描述符上可以写数据；<br>
epollpri：表示对应的文件描述符有紧急的数据可读（这里应该表示有带外数据到来）；<br>
epollerr：表示对应的文件描述符发生错误；<br>
epollhup： 表示对应的文件描述符被挂断；<br>
epollet：将epoll设为边缘触发(edgetriggered)模式，这是相对于水平触发(level triggered)来说的。<br>
epolloneshot： 只监听一次事件，当监听完这次事件之后，如果还需要继续监听这个socket的话，需要再次把这个socket加入到epoll队列里。</p>
<p>
示例：</p>
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<code class="cpp keyword bold">struct</code> <code class="cpp plain">epoll_event ev;</code>
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<code class="cpp comments">//设置与要处理的事件相关的文件描述符</code>
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<code class="cpp plain">ev.data.fd=listenfd;</code>
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<code class="cpp comments">//设置要处理的事件类型</code>
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<code class="cpp plain">ev.events=epollin|epollet;</code>
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<code class="cpp comments">//注册epoll事件</code>
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<code class="cpp plain">epoll_ctl(epfd,epoll_ctl_add,listenfd,&ev);</code>
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<p>
<strong>1.epoll_wait </strong></p>
<p>
等侍注册在epfd上的socket fd的事件的发生，如果发生则将发生的sokct fd和事件类型放入到events数组中。<br>
函数原型：<code>int epoll_wait(int epfd, struct epoll_event * events, int maxevents, int timeout); </code></p>
<p>
参数：<br>
epfd：由epoll_create 生成的epoll文件描述符<br>
events：用于回传代处理事件的数组<br>
maxevents：每次能处理的最大事件数<br>
timeout：等待i/o事件发生的超时毫秒数，-1相当于阻塞，0相当于非阻塞。一般用-1即可</p>
<p class="maodian"></p><h2>
epoll的工作模式</h2>
<p>
et(edgetriggered):高速工作模式，只支持no_block(非阻塞模式)。在此模式下，当描述符从未就绪变为就绪时，内核通过epoll告知。然后它会假设用户知道文件描述符已经就绪，并且不会再为那个文件描述符发送更多的就绪通知，直到某些操作导致那个文件描述符不再为就绪状态了。(触发模式只在数据就绪时通知一次，若数据没有读完，下一次不会通知，直到有新的就绪数据)</p>
<p>
lt(leveltriggered):缺省工作方式，支持blocksocket和no_blocksocket。在lt模式下内核会告知一个文件描述符是否就绪了，然后可以对这个就绪的fd进行io操作。如果不作任何操作，内核还是会继续通知！若数据没有读完，内核也会继续通知，直至设备数据为空为止！</p>
<p class="maodian"></p><h2>
示例说明：</h2>
<p>
1.我们已经把一个用来从管道中读取数据的文件句柄(rfd)添加到epoll描述符<br>
2. 这个时候从管道的另一端被写入了2kb的数据<br>
3. 调用epoll_wait(2)，并且它会返回rfd，说明它已经准备好读取操作<br>
4. 然后我们读取了1kb的数据<br>
5. 调用epoll_wait(2)……</p>
<p>
<strong>et工作模式： </strong></p>
<p>
如果我们在第1步将rfd添加到epoll描述符的时候使用了epollet标志，在第2步执行了一个写操作，第三步epoll_wait会返回同时通知的事件会销毁。因为第4步的读取操作没有读空文件输入缓冲区内的数据，因此我们在第5步调用epoll_wait(2)完成后，是否挂起是不确定的。epoll工作在et模式的时候，必须使用非阻塞套接口，以避免由于一个文件句柄的阻塞读/阻塞写操作把处理多个文件描述符的任务饿死。</p>
<p>
只有当read(2)或者write(2)返回eagain时(认为读完)才需要挂起，等待。但这并不是说每次read()时都需要循环读，直到读到产生一个eagain才认为此次事件处理完成，当read()返回的读到的数据长度小于请求的数据长度时(即小于sizeof(buf))，就可以确定此时缓冲中已没有数据了，也就可以认为此事读事件已处理完成。</p>
<p>
<strong>lt工作模式：</strong></p>
<p>
lt方式调用epoll接口的时候，它就相当于一个速度比较快的poll(2)，并且无论后面的数据是否被使用，因此他们具有同样的职能。</p>
<p class="maodian"></p><h2>
示例</h2>
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</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="cpp comments">/*</code>
</div>
<div class="line number2 index1 alt1">
<code class="cpp comments">* file epolltest.c</code>
</div>
<div class="line number3 index2 alt2">
<code class="cpp comments">*/</code>
</div>
<div class="line number4 index3 alt1">
<code class="cpp preprocessor">#include <stdio.h> </code>
</div>
<div class="line number5 index4 alt2">
<code class="cpp preprocessor">#include <stdlib.h> </code>
</div>
<div class="line number6 index5 alt1">
<code class="cpp preprocessor">#include <unistd.h> </code>
</div>
<div class="line number7 index6 alt2">
<code class="cpp preprocessor">#include <errno.h> </code>
</div>
<div class="line number8 index7 alt1">
<code class="cpp preprocessor">#include <sys/socket.h> </code>
</div>
<div class="line number9 index8 alt2">
<code class="cpp preprocessor">#include <netdb.h> </code>
</div>
<div class="line number10 index9 alt1">
<code class="cpp preprocessor">#include <fcntl.h> </code>
</div>
<div class="line number11 index10 alt2">
<code class="cpp preprocessor">#include <sys/epoll.h> </code>
</div>
<div class="line number12 index11 alt1">
<code class="cpp preprocessor">#include <string.h> </code>
</div>
<div class="line number13 index12 alt2">
</div>
<div class="line number14 index13 alt1">
<code class="cpp preprocessor">#define maxevents 64 </code>
</div>
<div class="line number15 index14 alt2">
</div>
<div class="line number16 index15 alt1">
<code class="cpp comments">//函数: </code>
</div>
<div class="line number17 index16 alt2">
<code class="cpp comments">//功能:创建和绑定一个tcp socket </code>
</div>
<div class="line number18 index17 alt1">
<code class="cpp comments">//参数:端口 </code>
</div>
<div class="line number19 index18 alt2">
<code class="cpp comments">//返回值:创建的socket </code>
</div>
<div class="line number20 index19 alt1">
<code class="cpp keyword bold">static</code> <code class="cpp color1 bold">int</code>
</div>
<div class="line number21 index20 alt2">
<code class="cpp plain">create_and_bind (</code><code class="cpp color1 bold">char</code> <code class="cpp plain">*port) </code>
</div>
<div class="line number22 index21 alt1">
<code class="cpp plain">{ </code>
</div>
<div class="line number23 index22 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">addrinfo hints; </code>
</div>
<div class="line number24 index23 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">addrinfo *result, *rp; </code>
</div>
<div class="line number25 index24 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">s, sfd; </code>
</div>
<div class="line number26 index25 alt1">
</div>
<div class="line number27 index26 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">memset</code> <code class="cpp plain">(&hints, 0, </code><code class="cpp keyword bold">sizeof</code> <code class="cpp plain">(</code><code class="cpp keyword bold">struct</code> <code class="cpp plain">addrinfo)); </code>
</div>
<div class="line number28 index27 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">hints.ai_family = af_unspec; </code><code class="cpp comments">/* return ipv4 and ipv6 choices */</code>
</div>
<div class="line number29 index28 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">hints.ai_socktype = sock_stream; </code><code class="cpp comments">/* we want a tcp socket */</code>
</div>
<div class="line number30 index29 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">hints.ai_flags = ai_passive; </code><code class="cpp comments">/* all interfaces */</code>
</div>
<div class="line number31 index30 alt2">
</div>
<div class="line number32 index31 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">s = getaddrinfo (null, port, &hints, &result); </code>
</div>
<div class="line number33 index32 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(s != 0) </code>
</div>
<div class="line number34 index33 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number35 index34 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">fprintf</code> <code class="cpp plain">(stderr, </code><code class="cpp string">"getaddrinfo: %s\n"</code><code class="cpp plain">, gai_strerror (s)); </code>
</div>
<div class="line number36 index35 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1; </code>
</div>
<div class="line number37 index36 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number38 index37 alt1">
</div>
<div class="line number39 index38 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">for</code> <code class="cpp plain">(rp = result; rp != null; rp = rp->ai_next) </code>
</div>
<div class="line number40 index39 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number41 index40 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">sfd = socket (rp->ai_family, rp->ai_socktype, rp->ai_protocol); </code>
</div>
<div class="line number42 index41 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(sfd == -1) </code>
</div>
<div class="line number43 index42 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">continue</code><code class="cpp plain">; </code>
</div>
<div class="line number44 index43 alt1">
</div>
<div class="line number45 index44 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">s = bind (sfd, rp->ai_addr, rp->ai_addrlen); </code>
</div>
<div class="line number46 index45 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(s == 0) </code>
</div>
<div class="line number47 index46 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number48 index47 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">/* we managed to bind successfully! */</code>
</div>
<div class="line number49 index48 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">break</code><code class="cpp plain">; </code>
</div>
<div class="line number50 index49 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number51 index50 alt2">
</div>
<div class="line number52 index51 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">close (sfd); </code>
</div>
<div class="line number53 index52 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number54 index53 alt1">
</div>
<div class="line number55 index54 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(rp == null) </code>
</div>
<div class="line number56 index55 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number57 index56 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">fprintf</code> <code class="cpp plain">(stderr, </code><code class="cpp string">"could not bind\n"</code><code class="cpp plain">); </code>
</div>
<div class="line number58 index57 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1; </code>
</div>
<div class="line number59 index58 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number60 index59 alt1">
</div>
<div class="line number61 index60 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">freeaddrinfo (result); </code>
</div>
<div class="line number62 index61 alt1">
</div>
<div class="line number63 index62 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">sfd; </code>
</div>
<div class="line number64 index63 alt1">
<code class="cpp plain">} </code>
</div>
<div class="line number65 index64 alt2">
</div>
<div class="line number66 index65 alt1">
</div>
<div class="line number67 index66 alt2">
<code class="cpp comments">//函数 </code>
</div>
<div class="line number68 index67 alt1">
<code class="cpp comments">//功能:设置socket为非阻塞的 </code>
</div>
<div class="line number69 index68 alt2">
<code class="cpp keyword bold">static</code> <code class="cpp color1 bold">int</code>
</div>
<div class="line number70 index69 alt1">
<code class="cpp plain">make_socket_non_blocking (</code><code class="cpp color1 bold">int</code> <code class="cpp plain">sfd) </code>
</div>
<div class="line number71 index70 alt2">
<code class="cpp plain">{ </code>
</div>
<div class="line number72 index71 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">flags, s; </code>
</div>
<div class="line number73 index72 alt2">
</div>
<div class="line number74 index73 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">//得到文件状态标志 </code>
</div>
<div class="line number75 index74 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">flags = fcntl (sfd, f_getfl, 0); </code>
</div>
<div class="line number76 index75 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(flags == -1) </code>
</div>
<div class="line number77 index76 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number78 index77 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">perror</code> <code class="cpp plain">(</code><code class="cpp string">"fcntl"</code><code class="cpp plain">); </code>
</div>
<div class="line number79 index78 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1; </code>
</div>
<div class="line number80 index79 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number81 index80 alt2">
</div>
<div class="line number82 index81 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">//设置文件状态标志 </code>
</div>
<div class="line number83 index82 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">flags |= o_nonblock; </code>
</div>
<div class="line number84 index83 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">s = fcntl (sfd, f_setfl, flags); </code>
</div>
<div class="line number85 index84 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(s == -1) </code>
</div>
<div class="line number86 index85 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number87 index86 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">perror</code> <code class="cpp plain">(</code><code class="cpp string">"fcntl"</code><code class="cpp plain">); </code>
</div>
<div class="line number88 index87 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">-1; </code>
</div>
<div class="line number89 index88 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number90 index89 alt1">
</div>
<div class="line number91 index90 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">0; </code>
</div>
<div class="line number92 index91 alt1">
<code class="cpp plain">} </code>
</div>
<div class="line number93 index92 alt2">
</div>
<div class="line number94 index93 alt1">
<code class="cpp comments">//端口由参数argv指定 </code>
</div>
<div class="line number95 index94 alt2">
<code class="cpp color1 bold">int</code>
</div>
<div class="line number96 index95 alt1">
<code class="cpp plain">main (</code><code class="cpp color1 bold">int</code> <code class="cpp plain">argc, </code><code class="cpp color1 bold">char</code> <code class="cpp plain">*argv[]) </code>
</div>
<div class="line number97 index96 alt2">
<code class="cpp plain">{ </code>
</div>
<div class="line number98 index97 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">sfd, s; </code>
</div>
<div class="line number99 index98 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">efd; </code>
</div>
<div class="line number100 index99 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">epoll_event event; </code>
</div>
<div class="line number101 index100 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">epoll_event *events; </code>
</div>
<div class="line number102 index101 alt1">
</div>
<div class="line number103 index102 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(argc != 2) </code>
</div>
<div class="line number104 index103 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number105 index104 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">fprintf</code> <code class="cpp plain">(stderr, </code><code class="cpp string">"usage: %s \n"</code><code class="cpp plain">, argv); </code>
</div>
<div class="line number106 index105 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">exit</code> <code class="cpp plain">(exit_failure); </code>
</div>
<div class="line number107 index106 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number108 index107 alt1">
</div>
<div class="line number109 index108 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">sfd = create_and_bind (argv); </code>
</div>
<div class="line number110 index109 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(sfd == -1) </code>
</div>
<div class="line number111 index110 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">abort</code> <code class="cpp plain">(); </code>
</div>
<div class="line number112 index111 alt1">
</div>
<div class="line number113 index112 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">s = make_socket_non_blocking (sfd); </code>
</div>
<div class="line number114 index113 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(s == -1) </code>
</div>
<div class="line number115 index114 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">abort</code> <code class="cpp plain">(); </code>
</div>
<div class="line number116 index115 alt1">
</div>
<div class="line number117 index116 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">s = listen (sfd, somaxconn); </code>
</div>
<div class="line number118 index117 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(s == -1) </code>
</div>
<div class="line number119 index118 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number120 index119 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">perror</code> <code class="cpp plain">(</code><code class="cpp string">"listen"</code><code class="cpp plain">); </code>
</div>
<div class="line number121 index120 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">abort</code> <code class="cpp plain">(); </code>
</div>
<div class="line number122 index121 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number123 index122 alt2">
</div>
<div class="line number124 index123 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">//除了参数size被忽略外,此函数和epoll_create完全相同 </code>
</div>
<div class="line number125 index124 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">efd = epoll_create1 (0); </code>
</div>
<div class="line number126 index125 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(efd == -1) </code>
</div>
<div class="line number127 index126 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number128 index127 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">perror</code> <code class="cpp plain">(</code><code class="cpp string">"epoll_create"</code><code class="cpp plain">); </code>
</div>
<div class="line number129 index128 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">abort</code> <code class="cpp plain">(); </code>
</div>
<div class="line number130 index129 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number131 index130 alt2">
</div>
<div class="line number132 index131 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">event.data.fd = sfd; </code>
</div>
<div class="line number133 index132 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">event.events = epollin | epollet;</code><code class="cpp comments">//读入,边缘触发方式 </code>
</div>
<div class="line number134 index133 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">s = epoll_ctl (efd, epoll_ctl_add, sfd, &event); </code>
</div>
<div class="line number135 index134 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(s == -1) </code>
</div>
<div class="line number136 index135 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number137 index136 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">perror</code> <code class="cpp plain">(</code><code class="cpp string">"epoll_ctl"</code><code class="cpp plain">); </code>
</div>
<div class="line number138 index137 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">abort</code> <code class="cpp plain">(); </code>
</div>
<div class="line number139 index138 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number140 index139 alt1">
</div>
<div class="line number141 index140 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">/* buffer where events are returned */</code>
</div>
<div class="line number142 index141 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">events = </code><code class="cpp functions bold">calloc</code> <code class="cpp plain">(maxevents, </code><code class="cpp keyword bold">sizeof</code> <code class="cpp plain">event); </code>
</div>
<div class="line number143 index142 alt2">
</div>
<div class="line number144 index143 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">/* the event loop */</code>
</div>
<div class="line number145 index144 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">while</code> <code class="cpp plain">(1) </code>
</div>
<div class="line number146 index145 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number147 index146 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">n, i; </code>
</div>
<div class="line number148 index147 alt1">
</div>
<div class="line number149 index148 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">n = epoll_wait (efd, events, maxevents, -1); </code>
</div>
<div class="line number150 index149 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">for</code> <code class="cpp plain">(i = 0; i < n; i++) </code>
</div>
<div class="line number151 index150 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number152 index151 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">((events.events & epollerr) || </code>
</div>
<div class="line number153 index152 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">(events.events & epollhup) || </code>
</div>
<div class="line number154 index153 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">(!(events.events & epollin))) </code>
</div>
<div class="line number155 index154 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number156 index155 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">/* an error has occured on this fd, or the socket is not </code>
</div>
<div class="line number157 index156 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">ready for reading (why were we notified then?) */</code>
</div>
<div class="line number158 index157 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">fprintf</code> <code class="cpp plain">(stderr, </code><code class="cpp string">"epoll error\n"</code><code class="cpp plain">); </code>
</div>
<div class="line number159 index158 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">close (events.data.fd); </code>
</div>
<div class="line number160 index159 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">continue</code><code class="cpp plain">; </code>
</div>
<div class="line number161 index160 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number162 index161 alt1">
</div>
<div class="line number163 index162 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">else</code> <code class="cpp keyword bold">if</code> <code class="cpp plain">(sfd == events.data.fd) </code>
</div>
<div class="line number164 index163 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number165 index164 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">/* we have a notification on the listening socket, which </code>
</div>
<div class="line number166 index165 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">means one or more incoming connections. */</code>
</div>
<div class="line number167 index166 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">while</code> <code class="cpp plain">(1) </code>
</div>
<div class="line number168 index167 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number169 index168 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">struct</code> <code class="cpp plain">sockaddr in_addr; </code>
</div>
<div class="line number170 index169 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">socklen_t in_len; </code>
</div>
<div class="line number171 index170 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">infd; </code>
</div>
<div class="line number172 index171 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">char</code> <code class="cpp plain">hbuf, sbuf; </code>
</div>
<div class="line number173 index172 alt2">
</div>
<div class="line number174 index173 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">in_len = </code><code class="cpp keyword bold">sizeof</code> <code class="cpp plain">in_addr; </code>
</div>
<div class="line number175 index174 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">infd = accept (sfd, &in_addr, &in_len); </code>
</div>
<div class="line number176 index175 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(infd == -1) </code>
</div>
<div class="line number177 index176 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number178 index177 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">((</code><code class="cpp functions bold">errno</code> <code class="cpp plain">== eagain) || </code>
</div>
<div class="line number179 index178 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">(</code><code class="cpp functions bold">errno</code> <code class="cpp plain">== ewouldblock)) </code>
</div>
<div class="line number180 index179 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number181 index180 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">/* we have processed all incoming </code>
</div>
<div class="line number182 index181 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">connections. */</code>
</div>
<div class="line number183 index182 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">break</code><code class="cpp plain">; </code>
</div>
<div class="line number184 index183 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number185 index184 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">else</code>
</div>
<div class="line number186 index185 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number187 index186 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">perror</code> <code class="cpp plain">(</code><code class="cpp string">"accept"</code><code class="cpp plain">); </code>
</div>
<div class="line number188 index187 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">break</code><code class="cpp plain">; </code>
</div>
<div class="line number189 index188 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number190 index189 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number191 index190 alt2">
</div>
<div class="line number192 index191 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">//将地址转化为主机名或者服务名 </code>
</div>
<div class="line number193 index192 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">s = getnameinfo (&in_addr, in_len, </code>
</div>
<div class="line number194 index193 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">hbuf, </code><code class="cpp keyword bold">sizeof</code> <code class="cpp plain">hbuf, </code>
</div>
<div class="line number195 index194 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">sbuf, </code><code class="cpp keyword bold">sizeof</code> <code class="cpp plain">sbuf, </code>
</div>
<div class="line number196 index195 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">ni_numerichost | ni_numericserv);</code><code class="cpp comments">//flag参数:以数字名返回 </code>
</div>
<div class="line number197 index196 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">//主机地址和服务地址 </code>
</div>
<div class="line number198 index197 alt1">
</div>
<div class="line number199 index198 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(s == 0) </code>
</div>
<div class="line number200 index199 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number201 index200 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">printf</code><code class="cpp plain">(</code><code class="cpp string">"accepted connection on descriptor %d "</code>
</div>
<div class="line number202 index201 alt1">
<code class="cpp spaces"> </code><code class="cpp string">"(host=%s, port=%s)\n"</code><code class="cpp plain">, infd, hbuf, sbuf); </code>
</div>
<div class="line number203 index202 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number204 index203 alt1">
</div>
<div class="line number205 index204 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">/* make the incoming socket non-blocking and add it to the </code>
</div>
<div class="line number206 index205 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">list of fds to monitor. */</code>
</div>
<div class="line number207 index206 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">s = make_socket_non_blocking (infd); </code>
</div>
<div class="line number208 index207 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(s == -1) </code>
</div>
<div class="line number209 index208 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">abort</code> <code class="cpp plain">(); </code>
</div>
<div class="line number210 index209 alt1">
</div>
<div class="line number211 index210 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">event.data.fd = infd; </code>
</div>
<div class="line number212 index211 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">event.events = epollin | epollet; </code>
</div>
<div class="line number213 index212 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">s = epoll_ctl (efd, epoll_ctl_add, infd, &event); </code>
</div>
<div class="line number214 index213 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(s == -1) </code>
</div>
<div class="line number215 index214 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number216 index215 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">perror</code> <code class="cpp plain">(</code><code class="cpp string">"epoll_ctl"</code><code class="cpp plain">); </code>
</div>
<div class="line number217 index216 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">abort</code> <code class="cpp plain">(); </code>
</div>
<div class="line number218 index217 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number219 index218 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number220 index219 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">continue</code><code class="cpp plain">; </code>
</div>
<div class="line number221 index220 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number222 index221 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">else</code>
</div>
<div class="line number223 index222 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number224 index223 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">/* we have data on the fd waiting to be read. read and </code>
</div>
<div class="line number225 index224 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">display it. we must read whatever data is available </code>
</div>
<div class="line number226 index225 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">completely, as we are running in edge-triggered mode </code>
</div>
<div class="line number227 index226 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">and won't get a notification again for the same </code>
</div>
<div class="line number228 index227 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">data. */</code>
</div>
<div class="line number229 index228 alt2">
<code class="cpp spaces"> </code><code class="cpp color1 bold">int</code> <code class="cpp plain">done = 0; </code>
</div>
<div class="line number230 index229 alt1">
</div>
<div class="line number231 index230 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">while</code> <code class="cpp plain">(1) </code>
</div>
<div class="line number232 index231 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number233 index232 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">ssize_t count; </code>
</div>
<div class="line number234 index233 alt1">
<code class="cpp spaces"> </code><code class="cpp color1 bold">char</code> <code class="cpp plain">buf; </code>
</div>
<div class="line number235 index234 alt2">
</div>
<div class="line number236 index235 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">count = read (events.data.fd, buf, </code><code class="cpp keyword bold">sizeof</code><code class="cpp plain">(buf)); </code>
</div>
<div class="line number237 index236 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(count == -1) </code>
</div>
<div class="line number238 index237 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number239 index238 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">/* if errno == eagain, that means we have read all </code>
</div>
<div class="line number240 index239 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">data. so go back to the main loop. */</code>
</div>
<div class="line number241 index240 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(</code><code class="cpp functions bold">errno</code> <code class="cpp plain">!= eagain) </code>
</div>
<div class="line number242 index241 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number243 index242 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">perror</code> <code class="cpp plain">(</code><code class="cpp string">"read"</code><code class="cpp plain">); </code>
</div>
<div class="line number244 index243 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">done = 1; </code>
</div>
<div class="line number245 index244 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number246 index245 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">break</code><code class="cpp plain">; </code>
</div>
<div class="line number247 index246 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number248 index247 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">else</code> <code class="cpp keyword bold">if</code> <code class="cpp plain">(count == 0) </code>
</div>
<div class="line number249 index248 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number250 index249 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">/* end of file. the remote has closed the </code>
</div>
<div class="line number251 index250 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">connection. */</code>
</div>
<div class="line number252 index251 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">done = 1; </code>
</div>
<div class="line number253 index252 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">break</code><code class="cpp plain">; </code>
</div>
<div class="line number254 index253 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number255 index254 alt2">
</div>
<div class="line number256 index255 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">/* write the buffer to standard output */</code>
</div>
<div class="line number257 index256 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">s = write (1, buf, count); </code>
</div>
<div class="line number258 index257 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(s == -1) </code>
</div>
<div class="line number259 index258 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number260 index259 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">perror</code> <code class="cpp plain">(</code><code class="cpp string">"write"</code><code class="cpp plain">); </code>
</div>
<div class="line number261 index260 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">abort</code> <code class="cpp plain">(); </code>
</div>
<div class="line number262 index261 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number263 index262 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number264 index263 alt1">
</div>
<div class="line number265 index264 alt2">
<code class="cpp spaces"> </code><code class="cpp keyword bold">if</code> <code class="cpp plain">(done) </code>
</div>
<div class="line number266 index265 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">{ </code>
</div>
<div class="line number267 index266 alt2">
<code class="cpp spaces"> </code><code class="cpp functions bold">printf</code> <code class="cpp plain">(</code><code class="cpp string">"closed connection on descriptor %d\n"</code><code class="cpp plain">, </code>
</div>
<div class="line number268 index267 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">events.data.fd); </code>
</div>
<div class="line number269 index268 alt2">
</div>
<div class="line number270 index269 alt1">
<code class="cpp spaces"> </code><code class="cpp comments">/* closing the descriptor will make epoll remove it </code>
</div>
<div class="line number271 index270 alt2">
<code class="cpp spaces"> </code><code class="cpp comments">from the set of descriptors which are monitored. */</code>
</div>
<div class="line number272 index271 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">close (events.data.fd); </code>
</div>
<div class="line number273 index272 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number274 index273 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number275 index274 alt2">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number276 index275 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">} </code>
</div>
<div class="line number277 index276 alt2">
</div>
<div class="line number278 index277 alt1">
<code class="cpp spaces"> </code><code class="cpp functions bold">free</code> <code class="cpp plain">(events); </code>
</div>
<div class="line number279 index278 alt2">
</div>
<div class="line number280 index279 alt1">
<code class="cpp spaces"> </code><code class="cpp plain">close (sfd); </code>
</div>
<div class="line number281 index280 alt2">
</div>
<div class="line number282 index281 alt1">
<code class="cpp spaces"> </code><code class="cpp keyword bold">return</code> <code class="cpp plain">exit_success; </code>
</div>
<div class="line number283 index282 alt2">
<code class="cpp plain">}</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
</div>
<p>
代码编译后，./epolltest 8888 ,在另外一个终端中执行<br><code>telnet 192.168.1.161 8888 ，192.168.1.161</code>为执行测试程序的ip。在telnet终端敲入任何字符敲入enter后，会在测试终端显示敲入的字符。</p>
<p class="maodian"></p><h2>
<span><strong>总结</strong></span>
</h2>
<p>
以上就是本文关于linux epoll机制详解的全部内容，希望对大家有所帮助。感兴趣的朋友可以继续参阅本站其他相关专题，如有不足之处，欢迎留言指出。感谢朋友们对本站的支持！</p>
<p>
原文链接：http://blog.csdn.net/u010657219/article/details/44061629</p>
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