Know which port are open in ubuntu.

Open Network Ports


It is important to know which ports are open on your computer. Ubuntu has a few tools to check this.



nmap



$ sudo nmap -T Aggressive 127.0.0.1 -p 1-65535



That will provide output similar to this:



Starting Nmap 4.53 ( http://insecure.org ) at 2008-12-08 12:57 EST

Interesting ports on localhost (127.0.0.1):

Not shown: 64995 closed ports

PORT STATE SERVICE

22/tcp open ssh

25/tcp open smtp



Nmap done: 1 IP address (1 host up) scanned in 2.674 seconds





netstat



$ sudo netstat -ln --ip



The output could be something like this:



Active Internet connections (only servers)

Proto Recv-Q Send-Q Local Address Foreign Address State

tcp 0 0 0.0.0.0:47724 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN

udp 0 0 0.0.0.0:48790 0.0.0.0:*

udp 0 0 0.0.0.0:46247 0.0.0.0:*

udp 0 0 0.0.0.0:68 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:*

raw 0 0 0.0.0.0:1 0.0.0.0:* 7





lsof



$ sudo lsof +M -i4



You will get an output like this:



COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME

portmap 4897 daemon 3u IPv4 13280 UDP *:111[portmapper]

portmap 4897 daemon 4u IPv4 13285 TCP *:111[portmapper] (LISTEN)

avahi-dae 5619 avahi 14u IPv4 14176 UDP *:5353

avahi-dae 5619 avahi 15u IPv4 14177 UDP *:48790

master 6400 root 11u IPv4 14925 TCP *:25 (LISTEN)

dhclient 6690 dhcp 6u IPv4 15927 UDP *:68

rpc.statd 9913 statd 6u IPv4 42812 UDP *:761

rpc.statd 9913 statd 8u IPv4 42819 UDP *:46247[status]

rpc.statd 9913 statd 9u IPv4 42822 TCP *:47724[status] (LISTEN)

cupsd 10062 root 2u IPv4 43034 TCP 127.0.0.1:631 (LISTEN)





fuser



Fuser, does help, but is not like the previous tools. With fuser you can also kill the process which is listening on a given port.



$ sudo fuser -v 3143/tcp



The output is:



USER PID ACCESS COMMAND

3143/tcp: www-data 2763 F.... apt-cacher





If you need to kill the process enter



$sudo fuser -vk 3143/tcp