Find which process is using a specific port

If you need to know/find which process is using a specific port on your system, you can use some default tools for troubleshooting:

• netstat
• lsof

: For the use of these tools, you will need root rights (or sudo rights will be efficient)

First, with netstat you can use options tnlpu to display much informations on connections:

$ sudo netstat -tlnpu
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:9000 0.0.0.0:* LISTEN 5786/php-fpm: pool
tcp 0 0 127.0.0.1:27017 0.0.0.0:* LISTEN 18591/mongod
tcp 0 0 0.0.0.0:8080 0.0.0.0:* LISTEN 15481/python
tcp 0 0 0.0.0.0:8081 0.0.0.0:* LISTEN 19238/nginx
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1105/sshd
tcp 0 0 127.0.0.1:5432 0.0.0.0:* LISTEN 15098/postgres
tcp6 0 0 :::22 :::* LISTEN 1105/sshd

Then, with lsof you can easily find which connections are opened on a specified port with the option -i on your command-line:

$ sudo lsof -i tcp:22
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
sshd 1054 root 3u IPv4 9672 0t0 TCP *:ssh (LISTEN)
sshd 1054 root 4u IPv6 9674 0t0 TCP *:ssh (LISTEN)
sshd 1146 root 3u IPv4 9794 0t0 TCP 192.168.56.101:ssh->192.168.56.1:49931 (ESTABLISHED)
sshd 1150 root 3u IPv4 9876 0t0 TCP 192.168.56.101:ssh->192.168.56.1:49933 (ESTABLISHED)
sshd 1254 admin 3u IPv4 9794 0t0 TCP 192.168.56.101:ssh->192.168.56.1:49931 (ESTABLISHED)
sshd 1265 admin 3u IPv4 9876 0t0 TCP 192.168.56.101:ssh->192.168.56.1:49933 (ESTABLISHED)