Recently we had written three articles similar to this topic.
The below articles will help you to check whether the given ports are open or not in the remote servers.
- check whether a port is open on the remote Linux system
- check whether a port is open on multiple remote Linux system
- check multiple ports status on multiple remote Linux system
In this article let us see how to check the list of open ports on the local system.
There are many utilities available in Linux for this purpose.However, I’m including top four Linux commands to check this.
It can be done using the following four commands. These are very famous and widely used by Linux admins.
netstat:netstat (“network statistics”) is a command-line tool that displays network connections related information (both incoming and outgoing) such as routing tables, masquerade connections, multicast memberships and a number of network interfacenmap:Nmap (“Network Mapper”) is an open source tool for network exploration and security auditing. It was designed to rapidly scan large networks.ss:ss is used to dump socket statistics. It shows information similar to netstat. It can display more TCP and state information than other tools.lsof:lsof stands for List Open File. It is used to print all the open files which is opened by process.
How to check list of open ports in Linux using netstat command?
netstat stands for Network Statistics, is a command-line tool that displays network connections related information (both incoming and outgoing) such as routing tables, masquerade connections, multicast memberships and a number of network interface.
It will list out all the tcp, udp socket connections and the unix socket connections.
It is used to diagnose network problems in the network and to determine the amount of traffic on the network as a performance measurement.
# netstat -tplugn Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 2038/master tcp 0 0 127.0.0.1:199 0.0.0.0:* LISTEN 1396/snmpd tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 1398/httpd tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1388/sshd tcp6 0 0 :::25 :::* LISTEN 2038/master tcp6 0 0 :::22 :::* LISTEN 1388/sshd udp 0 0 0.0.0.0:39136 0.0.0.0:* 1396/snmpd udp 0 0 0.0.0.0:56130 0.0.0.0:* 1396/snmpd udp 0 0 0.0.0.0:40105 0.0.0.0:* 1396/snmpd udp 0 0 0.0.0.0:11584 0.0.0.0:* 1396/snmpd udp 0 0 0.0.0.0:30105 0.0.0.0:* 1396/snmpd udp 0 0 0.0.0.0:50656 0.0.0.0:* 1396/snmpd udp 0 0 0.0.0.0:1632 0.0.0.0:* 1396/snmpd udp 0 0 0.0.0.0:28265 0.0.0.0:* 1396/snmpd udp 0 0 0.0.0.0:40764 0.0.0.0:* 1396/snmpd udp 0 0 10.90.56.21:123 0.0.0.0:* 895/ntpd udp 0 0 127.0.0.1:123 0.0.0.0:* 895/ntpd udp 0 0 0.0.0.0:123 0.0.0.0:* 895/ntpd udp 0 0 0.0.0.0:53390 0.0.0.0:* 1396/snmpd udp 0 0 0.0.0.0:161 0.0.0.0:* 1396/snmpd udp6 0 0 :::123 :::* 895/ntpd IPv6/IPv4 Group Memberships Interface RefCnt Group --------------- ------ --------------------- lo 1 224.0.0.1 eth0 1 224.0.0.1 lo 1 ff02::1 lo 1 ff01::1 eth0 1 ff02::1 eth0 1 ff01::1
If you would like to check any particular port status then use the following format.
# # netstat -tplugn | grep :22 tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1388/sshd tcp6 0 0 :::22 :::* LISTEN 1388/sshd
How to check list of open ports in Linux using ss Command?
ss is used to dump socket statistics. It will show information similar to netstat. It can display more TCP and state information than other tools.
# ss -lntu Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port udp UNCONN 0 0 *:39136 *:* udp UNCONN 0 0 *:56130 *:* udp UNCONN 0 0 *:40105 *:* udp UNCONN 0 0 *:11584 *:* udp UNCONN 0 0 *:30105 *:* udp UNCONN 0 0 *:50656 *:* udp UNCONN 0 0 *:1632 *:* udp UNCONN 0 0 *:28265 *:* udp UNCONN 0 0 *:40764 *:* udp UNCONN 0 0 10.90.56.21:123 *:* udp UNCONN 0 0 127.0.0.1:123 *:* udp UNCONN 0 0 *:123 *:* udp UNCONN 0 0 *:53390 *:* udp UNCONN 0 0 *:161 *:* udp UNCONN 0 0 :::123 :::* tcp LISTEN 0 100 *:25 *:* tcp LISTEN 0 128 127.0.0.1:199 *:* tcp LISTEN 0 128 *:80 *:* tcp LISTEN 0 128 *:22 *:* tcp LISTEN 0 100 :::25 :::* tcp LISTEN 0 128 :::22 :::*
If you would like to check any particular port status then use the following format.
# # ss -lntu | grep ':25' tcp LISTEN 0 100 *:25 *:* tcp LISTEN 0 100 :::25 :::*
How to check list of open ports in Linux using nmap Command?
Nmap (“Network Mapper”) is an open source tool for network exploration and security auditing. It was designed to rapidly scan large networks, although it works fine against single hosts.
Nmap uses raw IP packets in novel ways to determine which hosts are available on the network, whichservices (application name and version) those hosts are offering, which operating systems (and OS versions) they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics.
While Nmap is commonly used for security audits, many systems and network administrators find it useful for routine tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime.
# nmap -sTU -O localhost Starting Nmap 6.40 ( http://nmap.org ) at 2019-03-20 09:57 CDT Nmap scan report for localhost (127.0.0.1) Host is up (0.00028s latency). Other addresses for localhost (not scanned): 127.0.0.1 Not shown: 1994 closed ports PORT STATE SERVICE 22/tcp open ssh 25/tcp open smtp 80/tcp open http 199/tcp open smux 123/udp open ntp 161/udp open snmp Device type: general purpose Running: Linux 3.X OS CPE: cpe:/o:linux:linux_kernel:3 OS details: Linux 3.7 - 3.9 Network Distance: 0 hops OS detection performed. Please report any incorrect results at http://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 1.93 seconds
If you would like to check any particular port status then use the following format.
# nmap -sTU -O localhost | grep 123 123/udp open ntp
How to check list of open ports in Linux using lsof Command?
It shows you the list of open files on the system and the processes that opened them. Also shows you other information’s related to the files.
# lsof -i COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME ntpd 895 ntp 16u IPv4 18481 0t0 UDP *:ntp ntpd 895 ntp 17u IPv6 18482 0t0 UDP *:ntp ntpd 895 ntp 18u IPv4 18487 0t0 UDP localhost:ntp ntpd 895 ntp 20u IPv4 23020 0t0 UDP CentOS7.2daygeek.com:ntp sshd 1388 root 3u IPv4 20065 0t0 TCP *:ssh (LISTEN) sshd 1388 root 4u IPv6 20067 0t0 TCP *:ssh (LISTEN) snmpd 1396 root 6u IPv4 22739 0t0 UDP *:snmp snmpd 1396 root 7u IPv4 22729 0t0 UDP *:40105 snmpd 1396 root 8u IPv4 22730 0t0 UDP *:50656 snmpd 1396 root 9u IPv4 22731 0t0 UDP *:pammratc snmpd 1396 root 10u IPv4 22732 0t0 UDP *:30105 snmpd 1396 root 11u IPv4 22733 0t0 UDP *:40764 snmpd 1396 root 12u IPv4 22734 0t0 UDP *:53390 snmpd 1396 root 13u IPv4 22735 0t0 UDP *:28265 snmpd 1396 root 14u IPv4 22736 0t0 UDP *:11584 snmpd 1396 root 15u IPv4 22737 0t0 UDP *:39136 snmpd 1396 root 16u IPv4 22738 0t0 UDP *:56130 snmpd 1396 root 17u IPv4 22740 0t0 TCP localhost:smux (LISTEN) httpd 1398 root 3u IPv4 20337 0t0 TCP *:http (LISTEN) master 2038 root 13u IPv4 21638 0t0 TCP *:smtp (LISTEN) master 2038 root 14u IPv6 21639 0t0 TCP *:smtp (LISTEN) sshd 9052 root 3u IPv4 1419955 0t0 TCP CentOS7.2daygeek.com:ssh->Ubuntu18-04.2daygeek.com:11408 (ESTABLISHED) httpd 13371 apache 3u IPv4 20337 0t0 TCP *:http (LISTEN) httpd 13372 apache 3u IPv4 20337 0t0 TCP *:http (LISTEN) httpd 13373 apache 3u IPv4 20337 0t0 TCP *:http (LISTEN) httpd 13374 apache 3u IPv4 20337 0t0 TCP *:http (LISTEN) httpd 13375 apache 3u IPv4 20337 0t0 TCP *:http (LISTEN)
If you would like to check any particular port status then use the following format.
# lsof -i:80 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME httpd 1398 root 3u IPv4 20337 0t0 TCP *:http (LISTEN) httpd 13371 apache 3u IPv4 20337 0t0 TCP *:http (LISTEN) httpd 13372 apache 3u IPv4 20337 0t0 TCP *:http (LISTEN) httpd 13373 apache 3u IPv4 20337 0t0 TCP *:http (LISTEN) httpd 13374 apache 3u IPv4 20337 0t0 TCP *:http (LISTEN) httpd 13375 apache 3u IPv4 20337 0t0 TCP *:http (LISTEN)
