OpenBSD List Open TCP or UDP Network Ports

by on November 7, 2006 · 1 comment· LAST UPDATED November 27, 2012

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How do I find out open tcp or udp network ports under OpenBSD operating systems using command line options?

Tutorial details
DifficultyEasy (rss)
Root privilegesNo/Yes
Requirementsnetstat/fstat
Estimated completion timeN/A

You need to use the netstat command. This command display network status in various network-related data structures There are a number of output formats, depending on the options for the information presented. Another option is to use nmap command from a remote computer.

Task: Display tcp and UDP open port

Type the following command:
$ netstat -nat
OR
$ netstat -na -f inet
OR
$ netstat -na -f inet | grep LISTEN
OR
$ netstat -at | grep LISTEN
Sample outputs:

$ netstat -at | grep LISTEN
tcp        0      0  *.291                  *.*                    LISTEN
tcp        0      0  localhost.submissi     *.*                    LISTEN
tcp        0      0  localhost.smtp         *.*                    LISTEN
tcp        0      0  *.time                 *.*                    LISTEN
tcp        0      0  *.daytime              *.*                    LISTEN
tcp        0      0  *.auth                 *.*                    LISTEN
tcp6       0      0  *.ssh                  *.*                    LISTEN
tcp6       0      0  localhost.submissi     *.*                    LISTEN
tcp6       0      0  localhost.smtp         *.*                    LISTEN
tcp6       0      0  *.time                 *.*                    LISTEN
tcp6       0      0  *.daytime              *.*                    LISTEN
tcp6       0      0  *.auth                 *.*                    LISTEN

Just display IPv4 tcp ports, run:
$ netstat -f inet -at
Sample outputs:

Active Internet connections (including servers)
Proto Recv-Q Send-Q  Local Address          Foreign Address        (state)
tcp        0      0  openbsd.23087          resolver1.opendn.domai TIME_WAIT
tcp        0      0  openbsd.22            dsl-KK-dynamic-1.32789 ESTABLISHED
tcp        0    448  openbsd.22            dsl-KK-dynamic-1.32786 ESTABLISHED
tcp        0      0  *.22                  *.*                    LISTEN
tcp        0      0  localhost.submissi     *.*                    LISTEN
tcp        0      0  localhost.smtp         *.*                    LISTEN
tcp        0      0  *.time                 *.*                    LISTEN
tcp        0      0  *.daytime              *.*                    LISTEN
tcp        0      0  *.auth                 *.*                    LISTEN
Active Internet connections (including servers)
Proto Recv-Q Send-Q  Local Address          Foreign Address        (state)
udp        0      0  localhost.biff         *.*
udp        0      0  *.syslog               *.*

fstat command

You can use fstat command to find out more about port 22 or 80 as follows:
fstat | grep ':22'
Sample outputs:

root     sshd        7296    3* internet stream tcp 0xd538e334 192.168.1.115:22 <-- 192.168.1.5:43477
root     sshd        1358    3* internet6 stream tcp 0xd53a7000 *:22
root     sshd        1358    4* internet stream tcp 0xd53a7198 *:22

Other examples

To see information about the network interface:
$ netstat -i
Sample outputs:

Name    Mtu   Network     Address              Ipkts Ierrs    Opkts Oerrs Colls
lo0     33192                                6     0        6     0     0
lo0     33192 loopback    localhost.nixcraf        6     0        6     0     0
lo0     33192 localhost.n localhost.nixcraf        6     0        6     0     0
lo0     33192 fe80::%lo0/ fe80::1%lo0              6     0        6     0     0
pcn0    1500        00:0c:29:7b:66:72      560     0      485     0   124
pcn0    1500  75.126.68.4 openbsd.nixcraft.      560     0      485     0   124
pcn0    1500  fe80::%pcn0 fe80::20c:29ff:fe      560     0      485     0   124
pflog0* 33192                                0     0        0     0     0
pfsync0 1460                                 0     0        0     0     0
enc0*   1536                                 0     0        0     0     0

To see information about the specified interface called pcn0, run:
$ netstat -I pcn0

See how to use nmap to find out remote system open port. Read man page of netstat for more information.

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{ 1 comment… read it below or add one }

1 S!FE September 27, 2010 at 11:52 pm

sockstat -l -P tcp

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