【案例分析】Linux下如何查看端口占用情况

  作者：zhanhailiang 日期：2014-11-08

基于express写一个测试服务器代码如下，但是运行失败，报“listen EADDRINUSE”，字面上理解是error address in use，说明当前你监听的端口3000已经被使用了：

[root@~/wade/wadetest]# cat index.js 
var express = require('express');
var app = express();
 
app.get('/', function(req, res){
  res.send('hello world');
});
 
app.listen(3000, function() {
 
});
[root@~/wade/wadetest]# node index.js 
 
events.js:72
        throw er; // Unhandled 'error' event
              ^
Error: listen EADDRINUSE
    at errnoException (net.js:904:11)
    at Server._listen2 (net.js:1042:14)
    at listen (net.js:1064:10)
    at Server.listen (net.js:1138:5)
    at EventEmitter.app.listen (/root/wade/wadetest/node_modules/express/lib/application.js:559:24)
    at Object.<anonymous> (/root/wade/wadetest/index.js:8:5)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)

尝试使用netstat查看当前机器端口占用情况：

[root@~]# netstat -anop
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name    Timer
tcp        0      0 0.0.0.0:6379                0.0.0.0:*                   LISTEN      5906/redis-server * off (0.00/0/0)
tcp        0      0 127.0.0.1:11211             0.0.0.0:*                   LISTEN      8023/memcached      off (0.00/0/0)
tcp        0      0 0.0.0.0:6380                0.0.0.0:*                   LISTEN      26815/redis-server  off (0.00/0/0)
tcp        0      0 0.0.0.0:80                  0.0.0.0:*                   LISTEN      2720/nginx          off (0.00/0/0)
tcp        0      0 0.0.0.0:22                  0.0.0.0:*                   LISTEN      23854/sshd          off (0.00/0/0)
tcp        0      0 0.0.0.0:3000                0.0.0.0:*                   LISTEN      6732/node           off (0.00/0/0)
tcp        0      0 127.0.0.1:9000              0.0.0.0:*                   LISTEN      2466/php-fpm        off (0.00/0/0)
tcp        0      0 0.0.0.0:3690                0.0.0.0:*                   LISTEN      25447/svnserve      off (0.00/0/0)
tcp        0      0 0.0.0.0:3306                0.0.0.0:*                   LISTEN      23376/mysqld        off (0.00/0/0)

其中：

-n, --numeric              don't resolve names
-p, --programs             display PID/Program name for sockets
-a, --all, --listening     display all sockets (default: connected)
-o, --timers               display timers

由上可见，端口3000被PID为6732的node进程占用。

接下来通过ps查询该进程的详细信息：

[root@~]# ps -f -p 6732
UID        PID  PPID  C STIME TTY          TIME CMD
root      6732 6703  0 Nov02 ?        00:00:00 node /root/wade/git/node-lessons/lesson1/app.js
[root@~/wade/wadetest]# ps -fp 6703
UID        PID  PPID  C STIME TTY          TIME CMD
root      6703     1  0 Nov02 ?        00:00:00 pm2: Daemon

其中：

-f full 表示输出进程完整信息，如上所示
-p by process ID 表示查询指定进程ID

最后，kill掉进程6703或停止pm2服务即可正常运行上面的node示例：

[root@~/wade/git/node-lessons/lesson1]# pm2 kill
[PM2] Stopping PM2...
[PM2] Deleting all process
[PM2] deleteProcessId process id 0
[PM2] All processes has been stopped and deleted
[PM2] PM2 stopped
[root@~/wade/wadetest]# node index.js

如下图：