详解Linux 查看服务器开放的端口号
<p>在讨论这个问题前，我们先来了解一下物理端口、逻辑端口、端口号等计算机概念。</p>
<p>
<strong>端口相关的概念：</strong></p>
<p>
在网络技术中，端口（Port）包括逻辑端口和物理端口两种类型。物理端口指的是物理存在的端口，如ADSL Modem、集线器、交换机、路由器上用 于连接其他网络设备的接口，如RJ-45端口、SC端口等等。逻辑端口是指逻辑意义上用于区分服务的端口，如TCP/IP协议中的服务端口，端口号的范围从0到65535，比如用于浏览网页服务的80端口，用于FTP服务的21端口等。由于物理端口和逻辑端口数量较多，为了对端口进行区分，将每个端口进行了编号，这就是端口号</p>
<p>
端口按端口号可以分为3大类：</p>
<p>
1：公认端口（Well Known Port）</p>
<p>
公认端口号从0到1023，它们紧密绑定与一些常见服务，例如FTP服务使用端口21，你在 /etc/services 里面可以看到这种映射关系。 </p>
<p>
2：注册端口（Registered Ports): </p>
<p>
从1024到49151。它们松散地绑定于一些服务。也就是说有许多服务绑定于这些端口，这些端口同样用于许多其它目的.</p>
<p>
3: 动态或私有端口（Dynamic and/or Private Ports）</p>
<p>
动态端口，即私人端口号（private port numbers），是可用于任意软件与任何其他的软件通信的端口数，使用因特网的传输控制协议，或用户传输协议。动态端口一般从49152到65535</p>
<p>
Linux中有限定端口的使用范围，如果我要为我的程序预留某些端口，那么我需要控制这个端口范围。/proc/sys/net/ipv4/ip_local_port_range定义了本地TCP/UDP的端口范围，你可以在/etc/sysctl.conf里面定义net.ipv4.ip_local_port_range = 1024 65000</p>
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<code class="bash plain"></code><code class="bash comments"># cat /proc/sys/net/ipv4/ip_local_port_range</code>
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<code class="bash plain">32768 61000</code>
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<code class="bash plain"></code><code class="bash comments"># echo 1024 65535 > /proc/sys/net/ipv4/ip_local_port_range</code>
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关于端口和服务，我曾经拿公共厕所打比方，公共厕所里的每一个厕所就好比系统的每一个端口，为人解决方便就是所谓的服务，你提供了这些服务，那么就必须开放端口（厕所），当有人上厕所时，就是在这些端口建立了链接。如果那个厕所被人占用了，就表示端口号被服务占用了，如果有一天这里不提供公共厕所服务了，这个公共厕所被拆除了，自然也就没有了端口号了。其实更形象的例子，就好比银行大堂，端口号是那些柜台，而那些取号办理业务的人就好比链接到服务器的各种客户端。他们通过端口重定向技术与柜台发送业务联系。再举一个通俗易懂的例子，端口号，好比高铁线上的每个站点，例如，长沙、岳阳等分别代表一个端口号，旅客通过火车票到各自的站点，就好比各个应用程序发往服务器端口的IP包。</p>
<p>
<strong> 端口与服务的关系 </strong></p>
<p>
端口有什么用呢？我们知道，一台拥有IP地址的主机可以提供许多服务，比如Web服务、FTP服务、SMTP服务等，这些服务完全可以通过1个IP地址来实现。那么，主机是怎样区分不同的网络服务呢？显然不能只靠IP地址，因为IP 地址与网络服务的关系是一对多的关系。实际上是通过“IP地址+端口号”来区分不同的服务的。</p>
<p>
端口号与相应服务的对应关系存放在/etc/services文件中，这个文件中可以找到大部分端口。</p>
<p>
如何检查端口是否开放，其实不整理，还不知道有这么多方法！</p>
<p>
1：nmap工具检测开放端口</p>
<p>
nmap是一款网络扫描和主机检测的工具。nmap的安装非常简单，如下所示rpm安装所示。</p>
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<code class="bash plain"></code><code class="bash comments"># rpm -ivh nmap-4.11-1.1.x86_64.rpm </code>
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<code class="bash plain">warning: nmap-4.11-1.1.x86_64.rpm: Header V3 DSA signature: NOKEY, key ID 37017186</code>
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<code class="bash plain">Preparing... </code><code class="bash comments">########################################### </code>
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<code class="bash spaces"> </code><code class="bash plain">1:nmap </code><code class="bash comments">########################################### </code>
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<code class="bash plain"></code><code class="bash comments"># rpm -ivh nmap-frontend-4.11-1.1.x86_64.rpm </code>
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<code class="bash plain">warning: nmap-frontend-4.11-1.1.x86_64.rpm: Header V3 DSA signature: NOKEY, key ID 37017186</code>
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<code class="bash plain">Preparing... </code><code class="bash comments">########################################### </code>
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<code class="bash spaces"> </code><code class="bash plain">1:nmap-frontend </code><code class="bash comments">########################################### </code>
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<code class="bash plain"></code><code class="bash comments">#</code>
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<p>
关于nmap的使用，都可以长篇大写特写，这里不做展开。如下所示，nmap 127.0.0.1 查看本机开放的端口，会扫描所有端口。 当然也可以扫描其它服务器端口。</p>
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<code class="bash plain"></code><code class="bash comments"># nmap 127.0.0.1</code>
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<code class="bash plain">Starting Nmap 4.11 ( http:</code><code class="bash plain">//www</code><code class="bash plain">.insecure.org</code><code class="bash plain">/nmap/</code> <code class="bash plain">) at 2016-06-22 15:46 CST</code>
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<code class="bash plain">Interesting ports on localhost.localdomain (127.0.0.1):</code>
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<code class="bash plain">Not shown: 1674 closed ports</code>
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<code class="bash plain">PORT STATE SERVICE</code>
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<code class="bash plain">22</code><code class="bash plain">/tcp</code> <code class="bash functions">open</code> <code class="bash functions">ssh</code>
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<code class="bash plain">25</code><code class="bash plain">/tcp</code> <code class="bash functions">open</code> <code class="bash plain">smtp</code>
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<code class="bash plain">111</code><code class="bash plain">/tcp</code> <code class="bash functions">open</code> <code class="bash plain">rpcbind</code>
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<code class="bash plain">631</code><code class="bash plain">/tcp</code> <code class="bash functions">open</code> <code class="bash plain">ipp</code>
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<code class="bash plain">1011</code><code class="bash plain">/tcp</code> <code class="bash functions">open</code> <code class="bash plain">unknown</code>
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<code class="bash plain">3306</code><code class="bash plain">/tcp</code> <code class="bash functions">open</code> <code class="bash plain">mysql</code>
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<code class="bash spaces"> </code>
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<code class="bash plain">Nmap finished: 1 IP address (1 host up) scanned </code><code class="bash keyword">in</code> <code class="bash plain">0.089 seconds</code>
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<code class="bash plain">You have new mail </code><code class="bash keyword">in</code> <code class="bash plain">/var/spool/mail/root</code>
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<code class="bash plain"></code><code class="bash comments">#</code>
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<img title="详解Linux 查看服务器开放的端口号" alt="详解Linux 查看服务器开放的端口号" src="https://zhuji.jb51.net/uploads/img/202305/82c6ece86026547261b550194b6beb5b.jpg"></p>
<p>
2：netstat 工具检测开放端口</p>
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<code class="bash plain"></code><code class="bash comments"># netstat -anlp | grep 3306</code>
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<code class="bash plain">tcp 0 0 :::3306 :::* LISTEN 7358</code><code class="bash plain">/mysqld</code> </div>
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<code class="bash plain"></code><code class="bash comments"># netstat -anlp | grep 22</code>
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<code class="bash plain">tcp 0 0 :::22 :::* LISTEN 4020</code><code class="bash plain">/sshd</code> </div>
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<code class="bash plain">tcp 0 52 ::ffff:192.168.42.128:22 ::ffff:192.168.42.1:43561 ESTABLISHED 6198</code><code class="bash plain">/2</code> </div>
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<img title="详解Linux 查看服务器开放的端口号" alt="详解Linux 查看服务器开放的端口号" src="https://zhuji.jb51.net/uploads/img/202305/3aba89596a6710497397954d53472ea3.jpg"></p>
<p>
如上所示，这个工具感觉没有nmap简洁明了。当然也确实没有nmap功能强大。 </p>
<p>
3：lsof 工具检测开放端口</p>
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<code class="bash plain"></code><code class="bash comments"># service mysql start</code>
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<code class="bash plain">Starting MySQL......[ OK ]</code>
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<code class="bash plain"></code><code class="bash comments"># lsof -i:3306</code>
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<code class="bash plain">COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME</code>
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<code class="bash plain">mysqld 7860 mysql 15u IPv6 44714 TCP *:mysql (LISTEN)</code>
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<code class="bash plain"></code><code class="bash comments"># service mysql stop</code>
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<code class="bash plain">Shutting down MySQL..[ OK ]</code>
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<code class="bash plain"></code><code class="bash comments"># lsof -i:3306</code>
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<code class="bash plain"></code><code class="bash comments">#</code>
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<img title="详解Linux 查看服务器开放的端口号" alt="详解Linux 查看服务器开放的端口号" src="https://zhuji.jb51.net/uploads/img/202305/5630bd42be32e372b2f62a8455c6d2f9.jpg"></p>
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<code class="bash plain"></code><code class="bash comments"># lsof -i TCP| fgrep LISTEN</code>
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<code class="bash plain">cupsd 3153 root 4u IPv4 9115 TCP localhost.localdomain:ipp (LISTEN)</code>
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<code class="bash plain">portmap 3761 rpc 4u IPv4 10284 TCP *:sunrpc (LISTEN)</code>
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<code class="bash plain">rpc.statd 3797 rpcuser 7u IPv4 10489 TCP *:1011 (LISTEN)</code>
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<code class="bash plain">sshd 4020 root 3u IPv6 12791 TCP *:</code><code class="bash functions">ssh</code> <code class="bash plain">(LISTEN)</code>
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<code class="bash plain">sendmail 4042 root 4u IPv4 12876 TCP localhost.localdomain:smtp (LISTEN)</code>
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4： 使用telnet检测端口是否开放</p>
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服务器端口即使处于监听状态，但是防火墙iptables屏蔽了该端口，是无法通过该方法检测端口是否开放的。</p>
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5：netcat工具检测端口是否开放。</p>
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<code class="bash plain"></code><code class="bash comments"># nc -vv 192.168.42.128 1521</code>
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<code class="bash plain">Connection to 192.168.42.128 1521 port succeeded!</code>
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<code class="bash plain"></code><code class="bash comments"># nc -z 192.168.42.128 1521; echo $?</code>
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<code class="bash plain">Connection to 192.168.42.128 1521 port succeeded!</code>
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<code class="bash plain">0</code>
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<code class="bash plain"></code><code class="bash comments"># nc -vv 192.168.42.128 1433</code>
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<code class="bash plain">nc: connect to 192.168.42.128 port 1433 (tcp) failed: No route to host</code>
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<strong>关闭端口和开放端口 </strong></p>
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关闭端口和开放端口应该是两种不同的概念，每个端口都有对应的服务，因此要关闭端口，只要关闭相应的服务就可以了。像下面例子，开启了MySQL服务，端口3306处于监听状态，关闭MySQL服务后，端口3306自然被关闭了</p>
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<code class="bash plain"></code><code class="bash comments"># service mysql start</code>
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<code class="bash plain">Starting MySQL......[ OK ]</code>
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<code class="bash plain"></code><code class="bash comments"># lsof -i:3306</code>
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<div class="line number4 index3 alt1">
<code class="bash plain">COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME</code>
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<div class="line number5 index4 alt2">
<code class="bash plain">mysqld 7860 mysql 15u IPv6 44714 TCP *:mysql (LISTEN)</code>
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<div class="line number6 index5 alt1">
<code class="bash plain"></code><code class="bash comments"># service mysql stop</code>
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<div class="line number7 index6 alt2">
<code class="bash plain">Shutting down MySQL..[ OK ]</code>
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<div class="line number8 index7 alt1">
<code class="bash plain"></code><code class="bash comments"># lsof -i:3306</code>
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<div class="line number9 index8 alt2">
<code class="bash plain"></code><code class="bash comments">#</code>
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<textarea></textarea>
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<p>
所以，系统里面有些不必要的端口和服务，从安全考虑或资源节省角度，都应该关闭那些不必要的服务。关闭对应的端口。另外，即使服务开启，但是防火墙对对应的端口进行了限制，这样端口也不能被访问，但端口本身并没有关闭，只是端口被屏蔽了。</p>
<p>
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>
<p>
原文链接：http://www.cnblogs.com/kerrycode/p/5609010.html</p>
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