To be able to list for available service which is listening on Linux operating system distribution, it can be done by executing the appropriate command executed in any command line interface or terminal as long as it is being recognized by the shell.
The most popular command which can be used is ‘netstat’. The other one is by using ‘ss’. While netstat is more general on printing network connections, routing tables, interface statistics, etc, on the other hand ss is more specifically intended as a utility to investigate sockets.
In this article, we will discuss ‘netstat’ command usage with specific parameter. Below are theparameter usage passed to netstat command . First of all, the a netstat executed command in command line interface is typed as follow :
netstat -tulpn
The above executed command can be shown as follows :
root@hostname:/opt# netstat -tulpn Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN 29067/mysqld tcp 0 0 0.0.0.0:139 0.0.0.0:* LISTEN 2296/smbd tcp 0 0 127.0.0.1:6379 0.0.0.0:* LISTEN 1385/redis-server 1 tcp 0 0 127.0.0.1:11211 0.0.0.0:* LISTEN 1250/memcached tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN 947/rpcbind tcp 0 0 0.0.0.0:50000 0.0.0.0:* LISTEN 1552/monetdbd tcp 0 0 0.0.0.0:58324 0.0.0.0:* LISTEN 1291/rpc.mountd tcp 0 0 127.0.1.1:53 0.0.0.0:* LISTEN 28139/dnsmasq tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN 2313/dnsmasq tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1248/sshd tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 8790/cupsd tcp 0 0 127.0.0.1:3128 0.0.0.0:* LISTEN 1515/cntlm tcp 0 0 127.0.0.1:5432 0.0.0.0:* LISTEN 1128/postgres tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 3261/master tcp 0 0 0.0.0.0:5433 0.0.0.0:* LISTEN 1247/postgres tcp 0 0 0.0.0.0:445 0.0.0.0:* LISTEN 2296/smbd tcp 0 0 0.0.0.0:42688 0.0.0.0:* LISTEN 1291/rpc.mountd tcp 0 0 0.0.0.0:2049 0.0.0.0:* LISTEN - tcp 0 0 0.0.0.0:5666 0.0.0.0:* LISTEN 1581/nrpe tcp 0 0 0.0.0.0:39043 0.0.0.0:* LISTEN - tcp 0 0 0.0.0.0:55683 0.0.0.0:* LISTEN 1291/rpc.mountd tcp 0 0 127.0.0.1:27017 0.0.0.0:* LISTEN 1474/mongod tcp6 0 0 :::139 :::* LISTEN 2296/smbd tcp6 0 0 :::6379 :::* LISTEN 1516/redis-server * tcp6 0 0 :::53291 :::* LISTEN 1291/rpc.mountd tcp6 0 0 :::51758 :::* LISTEN 1291/rpc.mountd tcp6 0 0 :::111 :::* LISTEN 947/rpcbind tcp6 0 0 :::80 :::* LISTEN 1966/apache2 tcp6 0 0 :::56432 :::* LISTEN 1291/rpc.mountd tcp6 0 0 :::22 :::* LISTEN 1248/sshd tcp6 0 0 ::1:631 :::* LISTEN 8790/cupsd tcp6 0 0 :::25 :::* LISTEN 3261/master tcp6 0 0 :::5433 :::* LISTEN 1247/postgres tcp6 0 0 :::443 :::* LISTEN 1966/apache2 tcp6 0 0 :::445 :::* LISTEN 2296/smbd tcp6 0 0 :::2049 :::* LISTEN - tcp6 0 0 :::5666 :::* LISTEN 1581/nrpe tcp6 0 0 :::46280 :::* LISTEN - udp 0 0 192.168.1.100:49930 0.0.0.0:* 7316/dleyna-rendere udp 0 0 0.0.0.0:49994 0.0.0.0:* 1552/monetdbd udp 0 0 0.0.0.0:50000 0.0.0.0:* 1552/monetdbd udp 0 0 172.17.0.1:54117 0.0.0.0:* 7316/dleyna-rendere udp 0 0 0.0.0.0:33767 0.0.0.0:* 1291/rpc.mountd udp 0 0 127.0.0.1:50375 0.0.0.0:* 7316/dleyna-rendere udp 0 0 0.0.0.0:5353 0.0.0.0:* 20149/libpepflashpl udp 0 0 0.0.0.0:5353 0.0.0.0:* 998/avahi-daemon: r udp 0 0 0.0.0.0:42770 0.0.0.0:* - udp 0 0 239.255.255.250:1900 0.0.0.0:* 7316/dleyna-rendere udp 0 0 192.168.1.100:1900 0.0.0.0:* 7316/dleyna-rendere udp 0 0 239.255.255.250:1900 0.0.0.0:* 7316/dleyna-rendere udp 0 0 192.168.122.1:1900 0.0.0.0:* 7316/dleyna-rendere udp 0 0 239.255.255.250:1900 0.0.0.0:* 7316/dleyna-rendere udp 0 0 172.17.0.1:1900 0.0.0.0:* 7316/dleyna-rendere udp 0 0 239.255.255.250:1900 0.0.0.0:* 7316/dleyna-rendere udp 0 0 192.168.1.130:1900 0.0.0.0:* 7316/dleyna-rendere udp 0 0 239.255.255.250:1900 0.0.0.0:* 7316/dleyna-rendere udp 0 0 127.0.0.1:1900 0.0.0.0:* 7316/dleyna-rendere udp 0 0 0.0.0.0:2049 0.0.0.0:* - udp 0 0 192.168.122.1:59466 0.0.0.0:* 7316/dleyna-rendere udp 0 0 127.0.0.1:11211 0.0.0.0:* 1250/memcached udp 0 0 0.0.0.0:52485 0.0.0.0:* 1291/rpc.mountd udp 0 0 0.0.0.0:44369 0.0.0.0:* 998/avahi-daemon: r udp 0 0 192.168.1.130:53027 0.0.0.0:* 7316/dleyna-rendere udp 0 0 127.0.1.1:53 0.0.0.0:* 28139/dnsmasq udp 0 0 192.168.122.1:53 0.0.0.0:* 2313/dnsmasq udp 0 0 0.0.0.0:67 0.0.0.0:* 2313/dnsmasq udp 0 0 0.0.0.0:68 0.0.0.0:* 5321/dhclient udp 0 0 0.0.0.0:68 0.0.0.0:* 5307/dhclient udp 0 0 0.0.0.0:111 0.0.0.0:* 947/rpcbind udp 0 0 192.168.1.100:123 0.0.0.0:* 5841/ntpd udp 0 0 192.168.1.130:123 0.0.0.0:* 5841/ntpd udp 0 0 127.0.0.1:123 0.0.0.0:* 5841/ntpd udp 0 0 0.0.0.0:123 0.0.0.0:* 5841/ntpd udp 0 0 192.168.1.255:137 0.0.0.0:* 2110/nmbd udp 0 0 192.168.1.130:137 0.0.0.0:* 2110/nmbd udp 0 0 192.168.1.255:137 0.0.0.0:* 2110/nmbd udp 0 0 192.168.1.100:137 0.0.0.0:* 2110/nmbd udp 0 0 192.168.122.255:137 0.0.0.0:* 2110/nmbd udp 0 0 192.168.122.1:137 0.0.0.0:* 2110/nmbd udp 0 0 172.17.255.255:137 0.0.0.0:* 2110/nmbd udp 0 0 172.17.0.1:137 0.0.0.0:* 2110/nmbd udp 0 0 0.0.0.0:137 0.0.0.0:* 2110/nmbd udp 0 0 192.168.1.255:138 0.0.0.0:* 2110/nmbd udp 0 0 192.168.1.130:138 0.0.0.0:* 2110/nmbd udp 0 0 192.168.1.255:138 0.0.0.0:* 2110/nmbd udp 0 0 192.168.1.100:138 0.0.0.0:* 2110/nmbd udp 0 0 192.168.122.255:138 0.0.0.0:* 2110/nmbd udp 0 0 192.168.122.1:138 0.0.0.0:* 2110/nmbd udp 0 0 172.17.255.255:138 0.0.0.0:* 2110/nmbd udp 0 0 172.17.0.1:138 0.0.0.0:* 2110/nmbd udp 0 0 0.0.0.0:138 0.0.0.0:* 2110/nmbd udp 0 0 0.0.0.0:45314 0.0.0.0:* 1291/rpc.mountd udp 0 0 0.0.0.0:631 0.0.0.0:* 1142/cups-browsed udp 0 0 0.0.0.0:699 0.0.0.0:* 947/rpcbind udp6 0 0 :::46283 :::* 1291/rpc.mountd udp6 0 0 :::5353 :::* 998/avahi-daemon: r udp6 0 0 :::51118 :::* 1291/rpc.mountd udp6 0 0 :::2049 :::* - udp6 0 0 :::43520 :::* 1291/rpc.mountd udp6 0 0 :::35714 :::* 998/avahi-daemon: r udp6 0 0 :::52906 :::* - udp6 0 0 :::111 :::* 947/rpcbind udp6 0 0 fe80::2e0:4cff:fe53:123 :::* 5841/ntpd udp6 0 0 fe80::5e51:4fff:fe7:123 :::* 5841/ntpd udp6 0 0 fd08:63aa:7554:1:5e:123 :::* 5841/ntpd udp6 0 0 fd08:63aa:7554:1:25:123 :::* 5841/ntpd udp6 0 0 ::1:123 :::* 5841/ntpd udp6 0 0 :::123 :::* 5841/ntpd udp6 0 0 :::699 :::* 947/rpcbind root@hostname:/opt#
The output of the above command’s execution will be explained generally as follows :
Protocol : The first column explains the protocol used to transfer data which can be called as description of transfer protocol. There are two types of transfer protocol which is commonly used to be able transfer data over network. The first one is TCP (Transmission Control Protocol) and the latter is UDP (User Datagram Protocol). Both of them have their version 4 and version 6 respectively. It is marked with tcp for TCP protocol to support IP version 4, tcp6 for TCP protocol to support IP Version 6. And then udp for UDP protocol to support IP version 4, the last one is udp6 for UDP protocol to support IP version 6.
Recv-Q : It tells how much data waiting to be received for that socket. Normally it is zero, if it is non-zero there may be some trouble regarding application or program which is connected to the socket.
Send-Q : It tells how much data waiting to be sent for that socket. Normally it is also zero, when it is non-zero it represents data which cannot be processed by this host, server or workstation through the socket.
Local Address : Local end of the socket which is the address of the host, workstation, server or computer where netstat is running.
Foreign Address : Remote end of the socket which is the address of and the foreign end is about the other computer (could be somewhere in the local network or somewhere on the internet).
State : The state of the socket and there are several values for it.
PID/Program : It is the PID and also the name of the program to which each socket belongs.
There will be extraction of several output which is going to be explained further :
tcp 0 0 0.0.0.0:139 0.0.0.0:* LISTEN 2296/smbd
The above line shows that there is a service named smbd and it has PID number 2296. It is using protocol TCP and it actually listen in all interfaces in the local workstation, host or server. The state of the local socket is listening on port 139.
tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN 29067/mysqld
On the other hand, the above line can be read that there is a service named mysqld and it has PID number 29067. It is using protocol TCP and it actually listen only in loopback interface or only on local interface in the local workstation, host or server. The state of the local socket is listening on port 3306.
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