How to get active connections on a particular port in Linux ?
Here we will look how to get active connections on a particular port in Linux.
The active connections have a state “ESTABLISHED” when we look at the netstat output.
We can look the established connections via the command netstat and grepping established status.
I. NETSTAT Command
In netstat, we can grep established with particular port number.
[root@ngelinux ~]# netstat -anp | grep :22 | grep ESTABLISHED tcp 0 0 172.21.49.239:22 172.21.49.169:59940 ESTABLISHED 6780/sshd: root@pts tcp 0 0 172.21.49.239:22 172.21.49.169:56893 ESTABLISHED 4307/sshd: root@pts [root@ngelinux ~]#
II. LSOF Command
With lsof command, we can view the connections established i.e. active connections using below command.
$ lsof -i -P -n | grep ESTAB | grep :443 firefox 1819 saket 38u IPv4 0xdf0727d5ef06bd35 0t0 TCP 17.168.63.98:52521->216.58.196.163:443 (ESTABLISHED) firefox 1819 saket 39u IPv4 0xdf0727d5eed613e5 0t0 TCP 17.168.63.98:52533->74.125.68.189:443 (ESTABLISHED) firefox 1819 saket 40u IPv4 0xdf0727d5eed1d275 0t0 TCP 17.168.63.98:52869->216.58.196.174:443 (ESTABLISHED) firefox 1819 saket 89u IPv4 0xdf0727d5e9e29a55 0t0 TCP 17.168.63.98:52853->173.241.248.143:443 (ESTABLISHED) firefox 1819 saket 90u IPv4 0xdf0727d5e9e17105 0t0 TCP 17.168.63.98:52779->192.0.78.23:443 (ESTABLISHED) firefox 1819 saket 92u IPv4 0xdf0727d5eed1ad35 0t0 TCP 17.168.63.98:52861->172.217.163.174:443 (ESTABLISHED) firefox 1819 saket 94u IPv4 0xdf0727d5eed1e515 0t0 TCP 17.168.63.98:52819->172.217.166.110:443 (ESTABLISHED) firefox 1819 saket 96u IPv4 0xdf0727d5eed65515 0t0 TCP 17.168.63.98:52666->172.217.26.162:443 (ESTABLISHED) firefox 1819 saket 103u IPv4 0xdf0727d5eed63925 0t0 TCP 17.168.63.98:52675->172.217.163.34:443 (ESTABLISHED) firefox 1819 saket 117u IPv4 0xdf0727d5efd56105 0t0 TCP 17.168.63.98:52671->172.217.26.196:443 (ESTABLISHED) firefox 1819 saket 121u IPv4 0xdf0727d5e51c27b5 0t0 TCP 17.168.63.98:52876->192.0.76.3:443 (ESTABLISHED) firefox 1819 saket 122u IPv4 0xdf0727d5ed3a4e65 0t0 TCP 17.168.63.98:52834->104.20.186.5:443 (ESTABLISHED) firefox 1819 saket 124u IPv4 0xdf0727d5ebcf57b5 0t0 TCP 17.168.63.98:52817->172.217.163.163:443 (ESTABLISHED) firefox 1819 saket 127u IPv4 0xdf0727d5ead29fd5 0t0 TCP 17.168.63.98:52851->172.217.163.198:443 (ESTABLISHED) firefox 1819 saket 130u IPv4 0xdf0727d5eed3cd35 0t0 TCP 17.168.63.98:52372->198.252.206.25:443 (ESTABLISHED) firefox 1819 saket 146u IPv4 0xdf0727d5eed1b685 0t0 TCP 17.168.63.98:50063->52.42.195.146:443 (ESTABLISHED) firefox 1819 saket 152u IPv4 0xdf0727d5ed3a6a55 0t0 TCP 17.168.63.98:52879->52.27.55.66:443 (ESTABLISHED) firefox 1819 saket 173u IPv4 0xdf0727d5eed3f275 0t0 TCP 17.168.63.98:52821->216.58.197.66:443 (ESTABLISHED) firefox 1819 saket 177u IPv4 0xdf0727d5eed65e65 0t0 TCP 17.168.63.98:52823->216.58.197.66:443 (ESTABLISHED) firefox 1819 saket 185u IPv4 0xdf0727d5e51befd5 0t0 TCP 17.168.63.98:52824->172.217.167.129:443 (ESTABLISHED) firefox 1819 saket 199u IPv4 0xdf0727d5e9e17a55 0t0 TCP 17.168.63.98:52847->216.58.200.131:443 (ESTABLISHED) firefox 1819 saket 208u IPv4 0xdf0727d5ead29685 0t0 TCP 17.168.63.98:52757->216.58.197.37:443 (ESTABLISHED) firefox 1819 saket 217u IPv4 0xdf0727d5eed1dbc5 0t0 TCP 17.168.63.98:52716->172.217.167.138:443 (ESTABLISHED) com.apple 2350 saket 5u IPv4 0xdf0727d5eed61d35 0t0 TCP 17.168.63.98:52471->17.34.83.69:443 (ESTABLISHED) helpd 2948 saket 9u IPv4 0xdf0727d5eed1bfd5 0t0 TCP 17.168.63.98:52909->23.61.90.107:443 (ESTABLISHED) helpd 2948 saket 12u IPv4 0xdf0727d5ead283e5 0t0 TCP 17.168.63.98:52910->23.61.91.176:443 (ESTABLISHED) helpd 2948 saket 13u IPv4 0xdf0727d5ead2ea55 0t0 TCP 17.168.63.98:52911->23.61.91.176:443 (ESTABLISHED) helpd 2948 saket 14u IPv4 0xdf0727d5ed3a4515 0t0 TCP 17.168.63.98:52912->23.61.91.176:443 (ESTABLISHED) helpd 2948 saket 15u IPv4 0xdf0727d5ebcf6105 0t0 TCP 17.168.63.98:52913->23.61.91.176:443 (ESTABLISHED) ngelinux:~ saket$