I need a Linux command to list all free open ports for use in an application
lsof -i TCP| fgrep LISTEN
Does not seen to be helping as the Ports it lists are not necessarily free for use. How do I list free open ports not in use?
Super User is a question and answer site for computer enthusiasts and power users. It only takes a minute to sign up.
Sign up to join this communityI need a Linux command to list all free open ports for use in an application
lsof -i TCP| fgrep LISTEN
Does not seen to be helping as the Ports it lists are not necessarily free for use. How do I list free open ports not in use?
netstat -lntu
as replied by @askmish will give you list of services running on your system on tcp and udp ports where
-l
= only services which are listening on some port-n
= show port number, don't try to resolve the service name-t
= tcp ports-u
= udp ports-p
= name of the programYou don't need the 'p' parameter as you're only interested in getting which ports are free and not which program is running on it.
This only shows which ports on your system are used up, though. This doesn't tell you the status of your network e.g. if you're behind NAT and you want some services to be accessible from outside. Or if the firewall is blocking the port for outside visitors. In that case, nmap comes to the rescue. WARNING: Use nmap only on networks which are under your control. Also, there are firewall rules which can block nmap pings, you'll have to fiddle around with options to get correct results.
netstat
is deprecated on many systems and ss
should be used instead.
– Johu
Apr 19 '17 at 21:44
Since net-tools
is deprecated, you can use the ss
command instead of netstat
if netstat
is not present on your machine:
ss -lntu
should work similarly to
netstat -lntu
according to the built-in help:
-n, --numeric don't resolve service names
-l, --listening display listening sockets
-t, --tcp display only TCP sockets
-u, --udp display only UDP sockets
This command will list open network ports and the processes that own them:
netstat -lnptu
you can thereafter filter the results to your exact specs.
You could also use nmap
for more granular results about ports.
sudo netstat -lnptu
– klaus se
Oct 30 '14 at 1:17
All opened ports including response traffic:
netstat -tuwanp 2>/dev/null | awk '{print $4}' | sort | uniq -c | wc -l
netstat -tuwanp4 | awk '{print $4}' | grep ':' | cut -d ":" -f 2 | sort | uniq
– Aaron C. de Bruyn
Oct 9 '15 at 20:13
My take on the original question was that he was asking about the unused ports, not the ports currently connected to services. If this is the case, there's no specific way to list them, other than to listed the used ports and assume the others are unused.
One additional point to keep in mind: as a user, you'll not be able to open a port less than 1024 (you'll need root permissions for that).
The following command will work on any Unix which outputs in the same format as Ubuntu / Debian - where the local address is in the column 4 and the output includes a 2 line header at the top. If either of those numbers is different, tweak the awk command below.
If you want IPv4 only:
netstat -lnt | awk 'NR>2{print $4}' | grep -E '0.0.0.0:' | sed 's/.*://' | sort -n | uniq
If you want IPv6 only:
netstat -lnt | awk 'NR>2{print $4}' | grep -E ':::' | sed 's/.*://' | sort -n | uniq
If you want both together:
netstat -lnt | awk 'NR>2{print $4}' | grep -E '(0.0.0.0:|:::)' | sed 's/.*://' | sort -n | uniq
The command outputs a list of port numbers that are listening on all interfaces. If you want to list all ports that are listening on localhost interface, then use something like this:
netstat -lnt | awk 'NR>2{print $4}' | grep -E '(127.0.0.1:|::1:)' | sed 's/.*://' | sort -n | uniq
Try
sudo netstat -plnt | grep -E '(0.0.0.0:|:::|127.0.0.1:|::1:)' | awk 'NR>2{print $7}' | sort -n | uniq
and look at this.