Logo
Textual description of firstImageUrl

Linux open ports – How To

Linux open ports

There are many ways to identify open ports on Linux box.

1. Linux open ports using port scanning – nmap

Below nmap command lists TCP ports that are open,

linux-ts:/home/techsutram # nmap -sT 127.0.0.1

Starting Nmap 5.00 ( http://nmap.org ) at 2012-03-11 21:41 IST
mass_dns: warning: Unable to determine any DNS servers. Reverse DNS is disabled. Try using --system-dns or specify valid servers with --dns-servers
Interesting ports on localhost (127.0.0.1):
Not shown: 995 closed ports
PORT     STATE SERVICE
25/tcp   open  smtp
80/tcp   open  http
111/tcp  open  rpcbind
631/tcp  open  ipp
3306/tcp open  mysql

Nmap done: 1 IP address (1 host up) scanned in 0.37 seconds

Below nmap command lists UDP ports that are open,

linux-ts:/home/techsutram# nmap -sU 127.0.0.1

Starting Nmap 5.00 ( http://nmap.org ) at 2012-03-11 21:41 IST
mass_dns: warning: Unable to determine any DNS servers. Reverse DNS is disabled. Try using --system-dns or specify valid servers with --dns-servers
Interesting ports on localhost (127.0.0.1):
Not shown: 997 closed ports
PORT     STATE         SERVICE
111/udp  open|filtered rpcbind
631/udp  open|filtered ipp
5353/udp open|filtered zeroconf

Nmap done: 1 IP address (1 host up) scanned in 1.37 seconds

2. Linux open ports using command ‘lsof’

linux-techsutram:/home/techsutram # lsof -i
COMMAND    PID   USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
rpcbind   2680   root    6u  IPv4   9038      0t0  UDP *:sunrpc
rpcbind   2680   root    7u  IPv4   9049      0t0  UDP *:iris-xpc
rpcbind   2680   root    8u  IPv4   9050      0t0  TCP *:sunrpc (LISTEN)
rpcbind   2680   root    9u  IPv6   9052      0t0  UDP *:sunrpc
rpcbind   2680   root   10u  IPv6   9054      0t0  UDP *:iris-xpc
rpcbind   2680   root   11u  IPv6   9055      0t0  TCP *:sunrpc (LISTEN)
avahi-dae 2825  avahi   13u  IPv4   9451      0t0  UDP *:mdns
avahi-dae 2825  avahi   14u  IPv4   9452      0t0  UDP *:56745
cupsd     2845   root    4u  IPv6   9545      0t0  TCP localhost:ipp (LISTEN)
cupsd     2845   root    5u  IPv4   9546      0t0  TCP localhost:ipp (LISTEN)
cupsd     2845   root    7u  IPv4   9549      0t0  UDP *:ipp
mysqld    3182  mysql   10u  IPv4  10305      0t0  TCP *:mysql (LISTEN)
master    3605   root   12u  IPv4  11177      0t0  TCP localhost:smtp (LISTEN)
master    3605   root   13u  IPv6  11193      0t0  TCP localhost:smtp (LISTEN)
httpd2-pr 3774   root    3u  IPv4  11718      0t0  TCP *:http (LISTEN)
httpd2-pr 3775 wwwrun    3u  IPv4  11718      0t0  TCP *:http (LISTEN)
httpd2-pr 3776 wwwrun    3u  IPv4  11718      0t0  TCP *:http (LISTEN)
httpd2-pr 3777 wwwrun    3u  IPv4  11718      0t0  TCP *:http (LISTEN)
httpd2-pr 3778 wwwrun    3u  IPv4  11718      0t0  TCP *:http (LISTEN)
httpd2-pr 3779 wwwrun    3u  IPv4  11718      0t0  TCP *:http (LISTEN)

For each of the above named service, you can get their port numbers by going through /etc/services.

Below is the one liner that goes though /etc/services for every matched named service in lsof output,

linux-techsutram:/home/techsutram # for name in `lsof -i |  awk '{print $8":"$9}' | cut -d: -f3 | grep -v NAME | uniq `;do echo $name && grep -w ^$name /etc/services ;done

3. Linux open ports using 'socklist'

linux-techsutram:/home/techsutram # socklist
type   port      inode     uid    pid   fd  name
tcp     111       9050       0   2680    8  rpcbind
tcp      80      11718       0   3779    3  httpd2-prefork
tcp     631       9546       0   2845    5  cupsd
tcp      25      11177       0   3605   12  master
tcp    3306      10305      60   3182   10  mysqld
tcp6    111       9055       0   2680   11  rpcbind
tcp6    631       9545       0   2845    4  cupsd
tcp6     25      11193       0   3605   13  master
udp   56745       9452     109   2825   14  avahi-daemon
udp     713       9049       0   2680    7  rpcbind
udp    5353       9451     109   2825   13  avahi-daemon
udp     111       9038       0   2680    6  rpcbind
udp     631       9549       0   2845    7  cupsd
udp6    713       9054       0   2680   10  rpcbind
udp6    111       9052       0   2680    9  rpcbind

4.  Linux open ports using ‘netstat’

linux-techsutram:/home/techsutram # netstat -napl --tcp
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name  
tcp        0      0 0.0.0.0:111             0.0.0.0:*               LISTEN      2680/rpcbind       
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      3774/httpd2-prefork
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN      2845/cupsd         
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN      3605/master        
tcp        0      0 0.0.0.0:3306            0.0.0.0:*               LISTEN      3182/mysqld        
tcp        0      0 :::111                  :::*                    LISTEN      2680/rpcbind       
tcp        0      0 ::1:631                 :::*                    LISTEN      2845/cupsd         
tcp        0      0 ::1:25                  :::*                    LISTEN      3605/master        
linux-techsutram:/home/techsutram # netstat -napl --udp
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name  
udp        0      0 0.0.0.0:56745           0.0.0.0:*                           2825/avahi-daemon: 
udp        0      0 0.0.0.0:713             0.0.0.0:*                           2680/rpcbind       
udp        0      0 0.0.0.0:5353            0.0.0.0:*                           2825/avahi-daemon: 
udp        0      0 0.0.0.0:111             0.0.0.0:*                           2680/rpcbind       
udp        0      0 0.0.0.0:631             0.0.0.0:*                           2845/cupsd         
udp        0      0 :::713                  :::*                                2680/rpcbind       
udp        0      0 :::111                  :::*                                2680/rpcbind       

we can combine output of above two CLIs into single netstat command as,

linux-techsutram:/home/techsutram # netstat -napltu
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name  
tcp        0      0 0.0.0.0:111             0.0.0.0:*               LISTEN      2680/rpcbind       
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      3774/httpd2-prefork
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN      2845/cupsd         
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN      3605/master        
tcp        0      0 0.0.0.0:3306            0.0.0.0:*               LISTEN      3182/mysqld        
tcp        0      0 :::111                  :::*                    LISTEN      2680/rpcbind       
tcp        0      0 ::1:631                 :::*                    LISTEN      2845/cupsd         
tcp        0      0 ::1:25                  :::*                    LISTEN      3605/master        
udp        0      0 0.0.0.0:56745           0.0.0.0:*                           2825/avahi-daemon: 
udp        0      0 0.0.0.0:713             0.0.0.0:*                           2680/rpcbind       
udp        0      0 0.0.0.0:5353            0.0.0.0:*                           2825/avahi-daemon: 
udp        0      0 0.0.0.0:111             0.0.0.0:*                           2680/rpcbind       
udp        0      0 0.0.0.0:631             0.0.0.0:*                           2845/cupsd         
udp        0      0 :::713                  :::*                                2680/rpcbind       
udp        0      0 :::111                  :::*                                2680/rpcbind       


Don't be left Behind!
Sign up for daily updates delivered directly to your inbox.
Mandar Pise Opinions expressed by techsutram contributors are their own. More details

Mandar is a seasoned software professional for more than a decade. He is Cloud, AI, IoT, Blockchain and Fintech enthusiast. He writes to benefit others from his experiences. His overall goal is to help people learn about the Cloud, AI, IoT, Blockchain and Fintech and the effects they will have economically and socially in the future.

No comments:

Post a Comment

    Your valuable comments are welcome. (Moderated)


Instagram