Finding the PID of the process using a specific port?

Question

I am installing hadoop on my Ubuntu system. When I start it, it reports that port 9000 is busy.

I used:

netstat -nlp|grep 9000

to see if such a port exists and I got this:

   tcp        0      0 127.0.0.1:9000          0.0.0.0:*               LISTEN

But how can I get the PID of the process which is holding it?

Answer 1

Your existing command doesn't work because Linux requires you to either be root or the owner of the process to get the information you desire.

On modern systems, ss is the appropriate tool to use to get this information:

$ sudo ss -lptn 'sport = :80'
State   Local Address:Port  Peer Address:Port              
LISTEN  127.0.0.1:80        *:*                users:(("nginx",pid=125004,fd=12))
LISTEN  ::1:80              :::*               users:(("nginx",pid=125004,fd=11))

You can also use the same invocation you're currently using, but you must first elevate with sudo:

$ sudo netstat -nlp | grep :80
tcp  0  0  0.0.0.0:80  0.0.0.0:*  LISTEN  125004/nginx

You can also use lsof:

$ sudo lsof -n -i :80 | grep LISTEN
nginx   125004 nginx    3u  IPv4   6645      0t0  TCP 0.0.0.0:80 (LISTEN)

Answer 2

Also you can use lsof utility. Need to be root.

# lsof -i :25
COMMAND  PID        USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
exim4   2799 Debian-exim    3u  IPv4   6645      0t0  TCP localhost:smtp (LISTEN)
exim4   2799 Debian-exim    4u  IPv6   6646      0t0  TCP localhost:smtp (LISTEN)

Answer 3

I am using "CentOS 7 minimal" which has nor netstat neither lsof. But a lot of linux distributions have the socket statistics command (i.e. ss).

Here is an example of execution:

# ss -tanp | grep 6379
LISTEN   0    128  127.0.0.1:6379   *:*   users:(("redis-server",pid=2531,fd=4))

Answer 4

Running the command with sudo would give you the PID. On my development machine I get:

$ netstat -nlp | grep 8080
tcp6       0      0 :::8080      :::*       LISTEN      -

$ sudo netstat -nlp | grep 8080
tcp6       0      0 :::8080      :::*       LISTEN      16449/java

And as mentioned in other answers you can also use the ss or the lsof commands.

Answer 5

Also you can use fuser:

fuser -v -n tcp 22

The output :

                     USER        PID ACCESS COMMAND
22/tcp:              root        598 F.... sshd

Answer 6

I'm working on a Yocto Linux system that has a limited set of available Linux tools. I managed to find the process of a running port using the following commands (where I find the process using port 1883):

root@root:~# netstat -lt
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       
tcp        0      0 0.0.0.0:hostmon         0.0.0.0:*               LISTEN      
tcp        0      0 localhost.localdomain:domain 0.0.0.0:*               LISTEN      
tcp        0      0 0.0.0.0:9080            0.0.0.0:*               LISTEN      
tcp        0      0 0.0.0.0:1883            0.0.0.0:*               LISTEN      
tcp        0      0 :::hostmon              :::*                    LISTEN      
tcp        0      0 localhost:domain        :::*                    LISTEN      
tcp        0      0 :::ssh                  :::*                    LISTEN      
tcp        0      0 :::1883                 :::*                    LISTEN      
root@root:~# fuser 1883/tcp
290 
root@root:~# ps | grep 290
  290 mosquitt 25508 S    /usr/sbin/mosquitto -c /etc/mosquitto/mosquitto.conf
12141 root      8444 S    grep 290

As we can see above, it's the program /usr/sbin/mosquitto that's using port 1883.