Linux查看某个端口的连接数的方法
<p><strong>一、查看哪些IP连接本机</strong></p>
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<code class="bash functions">netstat</code> <code class="bash plain">-an</code>
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<strong>二、查看TCP连接数</strong></p>
<p>
1）统计80端口连接数</p>
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<code class="bash functions">netstat</code> <code class="bash plain">-nat | </code><code class="bash functions">grep</code> <code class="bash plain">-i </code><code class="bash string">"80"</code> <code class="bash plain">| </code><code class="bash functions">wc</code> <code class="bash plain">-l</code>
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2）统计httpd协议连接数</p>
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<code class="bash functions">ps</code> <code class="bash plain">-ef | </code><code class="bash functions">grep</code> <code class="bash plain">httpd | </code><code class="bash functions">wc</code> <code class="bash plain">-l</code>
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<p>
3）统计已连接上的，状态为“established</p>
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<code class="bash functions">netstat</code> <code class="bash plain">-anp | </code><code class="bash functions">grep</code> <code class="bash plain">ESTABLISHED | </code><code class="bash functions">wc</code> <code class="bash plain">-l</code>
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<p>
4)、查出哪个IP地址连接最多，将其封了</p>
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<code class="bash functions">netstat</code> <code class="bash plain">-anp | </code><code class="bash functions">grep</code> <code class="bash plain">ESTABLISHED | </code><code class="bash functions">awk</code> <code class="bash plain">{print $5}|</code><code class="bash functions">awk</code> <code class="bash plain">-F: {print $1} | </code><code class="bash functions">sort</code> <code class="bash plain">| </code><code class="bash functions">uniq</code> <code class="bash plain">-c | </code><code class="bash functions">sort</code> <code class="bash plain">-r +0n</code>
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<code class="bash functions">netstat</code> <code class="bash plain">-anp | </code><code class="bash functions">grep</code> <code class="bash plain">SYN | </code><code class="bash functions">awk</code> <code class="bash plain">{print $5}|</code><code class="bash functions">awk</code> <code class="bash plain">-F: {print $1} | </code><code class="bash functions">sort</code> <code class="bash plain">| </code><code class="bash functions">uniq</code> <code class="bash plain">-c | </code><code class="bash functions">sort</code> <code class="bash plain">-r +0n</code>
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<span><strong>实例：</strong></span></p>
<p>
1、查看Apache当前并发访问数：</p>
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<code class="bash functions">netstat</code> <code class="bash plain">-anp | </code><code class="bash functions">grep</code> <code class="bash plain">ESTABLISHED | </code><code class="bash functions">wc</code> <code class="bash plain">-l</code>
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<p>
对比httpd.conf中MaxClients的数字差距多少。</p>
<p>
2、查看有多少个进程数：</p>
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<code class="bash functions">ps</code> <code class="bash plain">aux | </code><code class="bash functions">grep</code> <code class="bash plain">httpd | </code><code class="bash functions">wc</code> <code class="bash plain">-l</code>
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<p>
3、可以使用如下参数查看数据</p>
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<code class="bash comments"># ps -ef | grep httpd | wc -l</code>
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<code class="bash plain">1388</code>
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<p>
统计httpd进程数，连个请求会启动一个进程，使用于Apache服务器。</p>
<p>
表示Apache能够处理1388个并发请求，这个值Apache可根据负载情况自动调整。</p>
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<code class="bash comments"># netstat -ant | grep -i "80" | wc -l</code>
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<code class="bash plain">4341</code>
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<p>
netstat -an会打印系统当前网络链接状态，而grep -i "80"是用来提取与80端口有关的连接的，wc -l进行连接数统计。最终返回的数字就是当前所有80端口的请求总数。</p>
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<code class="bash comments"># netstat -anp | grep ESTABLISHED | wc -l</code>
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<code class="bash plain">376</code>
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netstat -an会打印系统当前网络链接状态，而grep ESTABLISHED 提取出已建立连接的信息。 然后wc -l统计。最终返回的数字就是当前所有80端口的已建立连接的总数。</p>
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<code class="bash functions">netstat</code> <code class="bash plain">-ant || </code><code class="bash functions">grep</code> <code class="bash plain">ESTABLISHED | </code><code class="bash functions">wc</code> <code class="bash plain">-</code>
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<p>
可查看所有建立连接的详细记录</p>
<p>
查看Apache的并发请求数及其TCP连接状态：</p>
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<code class="plain plain"># netstat -n | awk '/^tcp/ {++S[$NF]} END {for(a in S) print a, S}'</code>
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<code class="plain plain">TIME_WAIT 8947 等待足够的时间以确保远程TCP接收到连接中断请求的确认</code>
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<code class="plain plain">FIN_WAIT1 15 等待远程TCP连接中断请求，或先前的连接中断请求的确认</code>
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<code class="plain plain">FIN_WAIT2 1 从远程TCP等待连接中断请求</code>
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<code class="plain plain">ESTABLISHED 55 代表一个打开的连接</code>
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<code class="plain plain">SYN_RECV 21 再收到和发送一个连接请求后等待对方对连接请求的确认</code>
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<code class="plain plain">CLOSING 2 没有任何连接状态</code>
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<code class="plain plain">LAST_ACK 4 等待原来的发向远程TCP的连接中断请求的确认</code>
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<p>
TCP连接状态详解</p>
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<li>
LISTEN： 侦听来自远方的TCP端口的连接请求</li>
<li>
SYN-SENT： 再发送连接请求后等待匹配的连接请求</li>
<li>
SYN-RECEIVED：再收到和发送一个连接请求后等待对方对连接请求的确认</li>
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ESTABLISHED： 代表一个打开的连接</li>
<li>
FIN-WAIT-1： 等待远程TCP连接中断请求，或先前的连接中断请求的确认</li>
<li>
FIN-WAIT-2： 从远程TCP等待连接中断请求</li>
<li>
CLOSE-WAIT： 等待从本地用户发来的连接中断请求</li>
<li>
CLOSING： 等待远程TCP对连接中断的确认</li>
<li>
LAST-ACK： 等待原来的发向远程TCP的连接中断请求的确认</li>
<li>
TIME-WAIT： 等待足够的时间以确保远程TCP接收到连接中断请求的确认</li>
<li>
CLOSED： 没有任何连接状态</li>
<li>
SYN_RECV表示正在等待处理的请求数；</li>
<li>
ESTABLISHED表示正常数据传输状态；</li>
<li>
TIME_WAIT表示处理完毕，等待超时结束的请求数。</li>
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<p>
4、如发现系统存在大量TIME_WAIT状态的连接，通过调整内核参数解决</p>
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<code class="bash plain">vim </code><code class="bash plain">/etc/sysctl</code><code class="bash plain">.conf</code>
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<p>
编辑文件，加入以下内容：</p>
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<code class="plain plain">net.ipv4.tcp_syncookies = 1</code>
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<code class="plain plain">net.ipv4.tcp_tw_reuse = 1</code>
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<code class="plain plain">net.ipv4.tcp_tw_recycle = 1</code>
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<code class="plain plain">net.ipv4.tcp_fin_timeout = 30</code>
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然后执行</p>
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<code class="plain plain">/sbin/sysctl -p</code>
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<p>
让参数生效。</p>
<p>
附上TIME_WAIT状态的意义：</p>
<ol>
<li>
net.ipv4.tcp_syncookies = 1 表示开启SYN cookies。当出现SYN等待队列溢出时，启用cookies来处理，可防范少量SYN攻击，默认为0，表示关闭；</li>
<li>
net.ipv4.tcp_tw_reuse = 1 表示开启重用。允许将TIME-WAIT sockets重新用于新的TCP连接，默认为0，表示关闭；</li>
<li>
net.ipv4.tcp_tw_recycle = 1 表示开启TCP连接中TIME-WAIT sockets的快速回收，默认为0，表示关闭。</li>
<li>
net.ipv4.tcp_fin_timeout 修改系統默认的TIMEOUT时间</li>
</ol>
<p>
5、客户端与服务器端建立TCP/IP连接后关闭SOCKET后，服务器端连接的端口状态为TIME_WAIT是不是所有执行主动关闭的socket都会进入TIME_WAIT状态呢？有没有什么情况使主动关闭的socket直接进入CLOSED状态呢？</p>
<p>
主动关闭的一方在发送最后一个ack后，就会进入TIME_WAIT状态停留2MSL（max segment lifetime）时间，这个是TCP/IP必不可少的，也就是“解决”不了的。也就是TCP/IP设计者本来是这么设计的。</p>
<p>
主要有两个原因：</p>
<p>
1、防止上一次连接中的包，迷路后重新出现，影响新连接（经过2MSL，上一次连接中所有的重复包都会消失）</p>
<p>
2、可靠的关闭TCP连接在主动关闭方发送的最后一个 ack(fin) ，有可能丢失，这时被动方会重新发fin, 如果这时主动方处于CLOSED状态 ，就会响应rst而不是ack。所以主动方要处于TIME_WAIT状态，而不能是CLOSED 。TIME_WAIT并不会占用很大资源的，除非受到攻击。还有，如果一方 send 或 recv 超时，就会直接进入 CLOSED 状态。</p>
<p>
6、如何合理设置Apache httpd的最大连接数？</p>
<p>
手头有一个网站在线人数增多，访问时很慢。初步认为是服务器资源不足了，但经反复测试，一旦连接上，不断点击同一个页面上不同的链接，都能迅速打开，这种现象就是说明apache最大连接数已经满了，新的访客只能排队等待有空闲的链接，而如果一旦连接上，在keeyalive 的存活时间内（KeepAliveTimeout，默认5秒）都不用重新打开连接，因此解决的方法就是加大apache的最大连接数。</p>
<p>
①.在哪里设置？</p>
<p>
apache 2.24，使用默认配置（FreeBSD 默认不加载自定义MPM配置），默认最大连接数是250</p>
<p>
在/usr/local/etc/apache22/httpd.conf中加载MPM配置（去掉前面的注释）：</p>
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<code class="plain plain"># Server-pool management (MPM specific)</code>
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<code class="plain plain">Include etc/apache22/extra/httpd-mpm.conf</code>
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可见的MPM配置在/usr/local/etc/apache22/extra/httpd-mpm.conf，但里面根据httpd的工作模式分了很多块，哪一部才是当前httpd的工作模式呢？可通过执行apachectl -l来查看：</p>
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<code class="plain plain">Compiled in modules:</code>
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<code class="plain spaces"> </code><code class="plain plain">core.c</code>
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<code class="plain spaces"> </code><code class="plain plain">prefork.c</code>
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<code class="plain spaces"> </code><code class="plain plain">http_core.c</code>
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看到prefork 字眼，因此可见当前httpd应该是工作在prefork模式，prefork模式的默认配置是：</p>
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<code class="xml plain"><</code><code class="xml keyword">IfModule</code> <code class="xml plain">mpm_prefork_module></code>
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<code class="xml spaces"> </code><code class="xml plain">StartServers 5</code>
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<code class="xml spaces"> </code><code class="xml plain">MinSpareServers 5</code>
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<code class="xml spaces"> </code><code class="xml plain">MaxSpareServers 10</code>
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<code class="xml spaces"> </code><code class="xml plain">MaxClients 150</code>
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②.要加到多少？</p>
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连接数理论上当然是支持越大越好，但要在服务器的能力范围内，这跟服务器的CPU、内存、带宽等都有关系。</p>
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查看当前的连接数可以用：</p>
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<code class="bash functions">ps</code> <code class="bash plain">aux | </code><code class="bash functions">grep</code> <code class="bash plain">httpd | </code><code class="bash functions">wc</code> <code class="bash plain">-l</code>
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或：</p>
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<code class="bash plain">pgrep httpd|</code><code class="bash functions">wc</code> <code class="bash plain">-l</code>
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计算httpd占用内存的平均数:</p>
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由于基本都是静态页面，CPU消耗很低，每进程占用内存也不算多，大约200K。</p>
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服务器内存有2G，除去常规启动的服务大约需要500M（保守估计），还剩1.5G可用，那么理论上可以支持1.5*1024*1024*1024/200000 = 8053.06368</p>
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约8K个进程，支持2W人同时访问应该是没有问题的（能保证其中8K的人访问很快，其他的可能需要等待1、2秒才能连上，而一旦连上就会很流畅）</p>
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控制最大连接数的MaxClients ，因此可以尝试配置为：</p>
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注意，MaxClients默认最大为250，若要超过这个值就要显式设置ServerLimit，且ServerLimit要放在MaxClients之前，值要不小于MaxClients，不然重启httpd时会有提示。</p>
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重启httpd后，通过反复执行pgrep httpd|wc -l 来观察连接数，可以看到连接数在达到MaxClients的设值后不再增加，但此时访问网站也很流畅，那就不用贪心再设置更高的值了，不然以后如果网站访问突增不小心就会耗光服务器内存，可根据以后访问压力趋势及内存的占用变化再逐渐调整，直到找到一个最优的设置值。</p>
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(MaxRequestsPerChild不能设置为0，可能会因内存泄露导致服务器崩溃）</p>
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更佳最大值计算的公式：</p>
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7、实时检测httpd连接数：</p>
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以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。</p>
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原文链接：http://www.cnblogs.com/EasonJim/p/8098532.html</p>
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