How do I find open ports on Linux / FreeBSD server?
There are different commands on both Linux and UNIX server to find out what tcp/udp ports are listening or open on your own server. You can use netstat command, which print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships etc. Another (and suggested) option is to use lsof command, which list open files, and ports on Linux, FreeBSD, Solaris and other Unixish systems.
netstat command to find open ports
# netstat --listen
To display open ports and established TCP connections, enter:
$ netstat -vatn
To display only open UDP ports try the following command:
$ netstat -vaun
If you want to see FQDN (full dns hostname), try removing the -n flag:
$ netstat -vat
lsof Command Examples
To display the list of open ports, enter:
# lsof -i
To display all open files, use:
# lsof
To display all open IPv4 network files in use by the process whose PID is 9255, use:
# lsof -i 4 -a -p 9255
A Note About FreeBSD Users
You can use the sockstat command lists open Internet or UNIX domain sockets, enter:
$ sockstat
$ sockstat -l
$ sockstat -4 -l
$ sockstat -6 -l
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{ 7 comments… read them below or add one }
I used lsof command in freebsd 5 i am not getting any output for checking tcp/udp ports which are listening or open on my server
sudo?
Yes, you must be root and use sockstat command.
What is the equivalent port for com9 on linux?How do i find out com port equivalents in linux?Thanks
on FreeBSD you can also use sockstat to list open sockets
correction :- should be
netstat -l, –listening :- to get list the listening sockets.
BR.
ruwinda.
lsof -i (to get an idea of ports out there)
netstat -a | grep
example: netstat -a | grep 4449
If nothing is returned like below the port is free
$ netstat -a | grep 4449
$