Tag Archives: open ports in unix

Open ports in Linux

How to list open ports on Linux/Unix server

Learn to list all open ports on Linux or Unix system. Also, view associated processes with them. A handy tip to troubleshoot service connectivity issues.

Many times in the life of sysadmin, you need to check which all ports open on your system. Sometimes you need to check if a particular port is listening on the server or not. If a particular service is communicating on a configured port or not. If a particular port has established connection or not.

All these things can be analysed with below commands.

netstat command :

Obviously first command is none other than netstat command. Use netstat with 4 options :

  • -a : Shows all sockets
  • -p : Show related PID
  • -t : TCP
  • -u : UDP
# netstat -ptau
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name
tcp        0      0 *:58573                     *:*                         LISTEN      1013/rpc.statd
tcp        0      0 *:sunrpc                    *:*                         LISTEN      991/rpcbind
tcp        0      0 *:ssh                       *:*                         LISTEN      1208/sshd
tcp        0      0 localhost:ipp               *:*                         LISTEN      1069/cupsd
tcp        0      0 localhost:smtp              *:*                         LISTEN      1287/master
tcp        0      0 ip-12-31-28-246.ap-:telnet 112.197.214.169:49648       ESTABLISHED 3213/in.telnetd
tcp        0      0 ip-12-31-28-246.ap-:telnet 200-163-187-49.scrce2:53440 ESTABLISHED 3215/in.telnetd
tcp        0      0 ip-12-31-28-246.ap-sou:ssh 59.182.17:49413             ESTABLISHED 1441/sshd
tcp        0    288 ip-12-31-28-246.ap-sou:ssh 59.182.17:50729             ESTABLISHED 1694/sshd
tcp        0      0 *:sunrpc                    *:*                         LISTEN      991/rpcbind
tcp        0      0 *:ssh                       *:*                         LISTEN      1208/sshd
tcp        0      0 *:telnet                    *:*                         LISTEN      1618/xinetd
tcp        0      0 localhost:ipp               *:*                         LISTEN      1069/cupsd
tcp        0      0 localhost:smtp              *:*                         LISTEN      1287/master
tcp        0      0 *:56954                     *:*                         LISTEN      1013/rpc.statd
udp        0      0 localhost:766               *:*                                     1013/rpc.statd
udp        0      0 *:39730                     *:*                                     1013/rpc.statd
udp        0      0 *:bootpc                    *:*                                     884/dhclient
udp        0      0 *:netrcs                    *:*                                     991/rpcbind
udp        0      0 *:sunrpc                    *:*                                     991/rpcbind
udp        0      0 *:ipp                       *:*                                     1069/cupsd
udp        0      0 *:60991                     *:*                                     1013/rpc.statd
udp        0      0 *:netrcs                    *:*                                     991/rpcbind
udp        0      0 *:sunrpc                    *:*                                     991/rpcbind

In above output you can see :

  • The first column is a protocol
  • Fourth column local address includes local IP, port, service
  • Fifth column destination IP, port, etc
  • The sixth column is the current state
  • The last column is PID and process name which owns that socket

Another way is to use netstat with an option:

# netstat -an
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address               Foreign Address             State
tcp        0      0 0.0.0.0:8001                0.0.0.0:*                   LISTEN
tcp        0      0 127.0.0.1:9633              0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:7937                0.0.0.0:*                   LISTEN
tcp        0      0 127.0.0.1:9634              0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:7938                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:9443                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:9444                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:9060                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:9061                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:14502               0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:14503               0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:8359                0.0.0.0:*                   LISTEN
tcp        0      0 127.0.0.1:199               0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:810                 0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:9100                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:9101                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:9133                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:111                 0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:8080                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:8880                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:6000                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:8881                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:9043                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:9044                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:21                  0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:22                  0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:9080                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:9081                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:2809                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:2810                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:443                 0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:6556                0.0.0.0:*                   LISTEN
tcp        0      0 10.10.5.160:42124         10.10.5.199:35994         ESTABLISHED
tcp        0      0 10.10.5.160:42376         10.10.5.199:39154         ESTABLISHED
tcp        0      0 10.10.5.160:8881          10.10.5.160:55117         TIME_WAIT
tcp        0      0 10.10.5.160:44367         10.10.5.199:48181         ESTABLISHED
tcp        0      0 10.10.5.160:36671         10.10.5.199:58137         ESTABLISHED
tcp        1      0 10.10.5.160:56253         10.10.5.160:9081          CLOSE_WAIT
tcp        0      0 10.10.5.160:57168         10.10.5.52:1521           ESTABLISHED
tcp        0      0 10.10.5.160:8880          10.10.5.160:55035         TIME_WAIT
tcp        0      0 10.10.5.160:6556          10.100.22.173:51544         ESTABLISHED
udp        0      0 0.0.0.0:7938                0.0.0.0:*
udp        0      0 0.0.0.0:37909               0.0.0.0:*
udp        0      0 0.0.0.0:161                 0.0.0.0:*
udp        0      0 0.0.0.0:804                 0.0.0.0:*
udp        0      0 0.0.0.0:807                 0.0.0.0:*
udp        0      0 0.0.0.0:177                 0.0.0.0:*
udp        0      0 0.0.0.0:5353                0.0.0.0:*
udp        0      0 0.0.0.0:111                 0.0.0.0:*
udp        0      0 203.127.98.134:123          0.0.0.0:*
udp        0      0 10.10.5.160:123           0.0.0.0:*
udp        0      0 127.0.0.1:123               0.0.0.0:*
udp        0      0 0.0.0.0:123                 0.0.0.0:*
Active UNIX domain sockets (servers and established)
Proto RefCnt Flags       Type       State         I-Node Path
unix  2      [ ACC ]     STREAM     LISTENING     7690   @ISCSIADM_ABSTRACT_NAMESPACE
unix  2      [ ACC ]     STREAM     LISTENING     11363  @/tmp/fam-root-
unix  2      [ ACC ]     STREAM     LISTENING     11003  /var/run/avahi-daemon/socket
unix  2      [ ACC ]     STREAM     LISTENING     8701   @/var/run/hald/dbus-RL64SjEdUd
unix  2      [ ACC ]     STREAM     LISTENING     247409367 /jas/HTTPServer/logs/cgisock.14073
unix  2      [ ACC ]     STREAM     LISTENING     247409370 /jas/HTTPServer/logs/siddport
unix  2      [ ACC ]     STREAM     LISTENING     11221  /tmp/.gdm_socket
unix  14     [ ]         DGRAM                    8008   /dev/log
unix  2      [ ACC ]     STREAM     LISTENING     7668   @ISCSID_UIP_ABSTRACT_NAMESPACE
unix  2      [ ]         DGRAM                    1797   @/org/kernel/udev/udevd
unix  2      [ ]         DGRAM                    8709   @/org/freedesktop/hal/udev_event
unix  2      [ ACC ]     STREAM     LISTENING     8700   @/var/run/hald/dbus-mO28j2Fpoe
unix  2      [ ACC ]     STREAM     LISTENING     7963   /var/run/audispd_events
unix  2      [ ACC ]     STREAM     LISTENING     10761  /tmp/.font-unix/fs7100
unix  2      [ ACC ]     STREAM     LISTENING     10709  /dev/gpmctl
unix  2      [ ACC ]     STREAM     LISTENING     8608   /var/run/dbus/system_bus_socket
unix  2      [ ACC ]     STREAM     LISTENING     8675   /var/run/acpid.socket
unix  2      [ ACC ]     STREAM     LISTENING     11248  /tmp/.X11-unix/X0
unix  2      [ ]         DGRAM                    322339652
unix  2      [ ]         STREAM     CONNECTED     284330078
unix  2      [ ]         STREAM     CONNECTED     83187468
unix  2      [ ]         DGRAM                    11482214
unix  2      [ ]         STREAM     CONNECTED     98040
unix  3      [ ]         STREAM     CONNECTED     11366  @/tmp/fam-root-
unix  3      [ ]         STREAM     CONNECTED     11365
unix  3      [ ]         STREAM     CONNECTED     11356  /var/run/dbus/system_bus_socket
unix  3      [ ]         STREAM     CONNECTED     11355
unix  3      [ ]         STREAM     CONNECTED     11333  /tmp/.X11-unix/X0
unix  3      [ ]         STREAM     CONNECTED     11332
unix  3      [ ]         STREAM     CONNECTED     11306  /tmp/.X11-unix/X0
unix  3      [ ]         STREAM     CONNECTED     11305
unix  3      [ ]         STREAM     CONNECTED     11283  /tmp/.font-unix/fs7100
unix  3      [ ]         STREAM     CONNECTED     11282
unix  2      [ ]         DGRAM                    11254
unix  3      [ ]         STREAM     CONNECTED     11286  /tmp/.X11-unix/X0
unix  3      [ ]         STREAM     CONNECTED     11253
unix  3      [ ]         STREAM     CONNECTED     11252  /var/run/acpid.socket
unix  3      [ ]         STREAM     CONNECTED     11251
unix  3      [ ]         STREAM     CONNECTED     11006  /var/run/dbus/system_bus_socket
unix  3      [ ]         STREAM     CONNECTED     11005
unix  3      [ ]         STREAM     CONNECTED     11000
unix  3      [ ]         STREAM     CONNECTED     10999
unix  2      [ ]         DGRAM                    10997
unix  2      [ ]         DGRAM                    10851
unix  2      [ ]         DGRAM                    10686
unix  2      [ ]         DGRAM                    10661
unix  2      [ ]         DGRAM                    10594
unix  2      [ ]         DGRAM                    10569
unix  2      [ ]         DGRAM                    10453
unix  3      [ ]         STREAM     CONNECTED     10344  /var/run/dbus/system_bus_socket
unix  3      [ ]         STREAM     CONNECTED     10343
unix  3      [ ]         STREAM     CONNECTED     10298  @/var/run/hald/dbus-mO28j2Fpoe
unix  3      [ ]         STREAM     CONNECTED     10297
unix  3      [ ]         STREAM     CONNECTED     10117  @/var/run/hald/dbus-mO28j2Fpoe
unix  3      [ ]         STREAM     CONNECTED     10113
unix  3      [ ]         STREAM     CONNECTED     10096  /var/run/acpid.socket
unix  3      [ ]         STREAM     CONNECTED     10093
unix  3      [ ]         STREAM     CONNECTED     10063  @/var/run/hald/dbus-mO28j2Fpoe
unix  3      [ ]         STREAM     CONNECTED     10059
unix  3      [ ]         STREAM     CONNECTED     8704   @/var/run/hald/dbus-RL64SjEdUd
unix  3      [ ]         STREAM     CONNECTED     8703
unix  3      [ ]         STREAM     CONNECTED     8612
unix  3      [ ]         STREAM     CONNECTED     8611
unix  3      [ ]         STREAM     CONNECTED     8466
unix  3      [ ]         STREAM     CONNECTED     8465
unix  2      [ ]         DGRAM                    8343
unix  2      [ ]         DGRAM                    8016
unix  3      [ ]         STREAM     CONNECTED     7954
unix  3      [ ]         STREAM     CONNECTED     7953

lsof command :

Using lsof command also you can trace current open ports on the system. lsof mainly lists open files. Since sockets are treated as network files at the kernel level and they are treated as open when communicating, sockets can be listed using lsof!

lsof has -i option specifically to list network files.

# lsof -i
COMMAND    PID     USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
dhclient   884     root    5u  IPv4  10791      0t0  UDP *:bootpc
rpcbind    991      rpc    6u  IPv4  11109      0t0  UDP *:sunrpc
rpcbind    991      rpc    7u  IPv4  11111      0t0  UDP *:netrcs
rpcbind    991      rpc    8u  IPv4  11112      0t0  TCP *:sunrpc (LISTEN)
rpcbind    991      rpc    9u  IPv6  11114      0t0  UDP *:sunrpc
rpcbind    991      rpc   10u  IPv6  11116      0t0  UDP *:netrcs
rpcbind    991      rpc   11u  IPv6  11117      0t0  TCP *:sunrpc (LISTEN)
rpc.statd 1013  rpcuser    6u  IPv4  11206      0t0  UDP localhost:766
rpc.statd 1013  rpcuser    7u  IPv4  11210      0t0  UDP *:39730
rpc.statd 1013  rpcuser    8u  IPv4  11214      0t0  TCP *:58573 (LISTEN)
rpc.statd 1013  rpcuser    9u  IPv6  11218      0t0  UDP *:60991
rpc.statd 1013  rpcuser   10u  IPv6  11222      0t0  TCP *:56954 (LISTEN)
cupsd     1069     root    6u  IPv6  11412      0t0  TCP localhost:ipp (LISTEN)
cupsd     1069     root    7u  IPv4  11413      0t0  TCP localhost:ipp (LISTEN)
cupsd     1069     root    9u  IPv4  11416      0t0  UDP *:ipp
sshd      1208     root    3u  IPv4  11960      0t0  TCP *:ssh (LISTEN)
sshd      1208     root    4u  IPv6  11962      0t0  TCP *:ssh (LISTEN)
master    1287     root   11u  IPv4  12158      0t0  TCP localhost:smtp (LISTEN)
master    1287     root   12u  IPv6  12160      0t0  TCP localhost:smtp (LISTEN)
sshd      1441     root    3r  IPv4  12964      0t0  TCP ip-12-31-28-246.ap-south-1.compute.internal:ssh-59.184.179.68:49413 (ESTABLISHED)
sshd      1444 ec2-user    3u  IPv4  12964      0t0  TCP ip-12-31-28-246.ap-south-1.compute.internal:ssh-59.184.179.68:49413 (ESTABLISHED)
xinetd    1618     root    5u  IPv6  13908      0t0  TCP *:telnet (LISTEN)
sshd      1694     root    3r  IPv4  14812      0t0  TCP ip-12-31-28-246.ap-south-1.compute.internal:ssh-59.184.179.68:50729 (ESTABLISHED)
sshd      1697 ec2-user    3u  IPv4  14812      0t0  TCP ip-12-31-28-246.ap-south-1.compute.internal:ssh-59.184.179.68:50729 (ESTABLISHED)
in.telnet 3420     root    0u  IPv4  35294      0t0  TCP ip-12-31-28-246.ap-south-1.compute.internal:telnet->5ec3c900.skybroadband.com:39192 (ESTABLISHED)
in.telnet 3420     root    1u  IPv4  35294      0t0  TCP ip-12-31-28-246.ap-south-1.compute.internal:telnet->5ec3c900.skybroadband.com:39192 (ESTABLISHED)
in.telnet 3420     root    2u  IPv4  35294      0t0  TCP ip-12-31-28-246.ap-south-1.compute.internal:telnet->5ec3c900.skybroadband.com:39192 (ESTABLISHED)
in.telnet 3422     root    0u  IPv4  35326      0t0  TCP ip-12-31-28-246.ap-south-1.compute.internal:telnet->188-24-133-29.dynamic.brasov.rdsnet.ro:apwi-rxserver (ESTABLISHED)
in.telnet 3422     root    1u  IPv4  35326      0t0  TCP ip-12-31-28-246.ap-south-1.compute.internal:telnet->188-24-133-29.dynamic.brasov.rdsnet.ro:apwi-rxserver (ESTABLISHED)
in.telnet 3422     root    2u  IPv4  35326      0t0  TCP ip-12-31-28-246.ap-south-1.compute.internal:telnet->188-24-133-29.dynamic.brasov.rdsnet.ro:apwi-rxserver (ESTABLISHED)

In the above output, you can see which command being run by which user using which socket and state of the port at the end!

If you have any other trick to list open ports on the system, please let us know in the comments. We will add it to this post.