There are different commands on both Linux and UNIX server to see what TCP\/UDP ports are listening or open on your server. You can use netstat command, which prints network connections, routing tables, interface statistics, masquerade connections, and multicast memberships, etc.<\/p>\n
Method 1:<\/b><\/p>\n
netstat command to find open ports<\/b><\/p>\n
ravi@linuxforfreshers.com>>sudo netstat –listen<\/p>\n
Active Internet connections (only servers)<\/p>\n
Proto Recv-Q Send-Q Local Address Foreign Address State<\/p>\n
tcp 0 0 *:1234 *:* LISTEN<\/p>\n
tcp 0 0 *:8084 *:* LISTEN<\/p>\n
tcp 0 0 192.168.122.1:domain *:* LISTEN<\/p>\n
tcp 0 0 *:ssh *:* LISTEN<\/p>\n
tcp 0 0 *:ipp *:* LISTEN<\/p>\n
tcp 0 0 *:microsoft-ds *:* LISTEN<\/p>\n
tcp 0 0 *:7070 *:* LISTEN<\/p>\n
tcp 0 0 localhost:mysql *:* LISTEN<\/p>\n
tcp 0 0 *:netbios-ssn *:* LISTEN<\/p>\n
tcp6 0 0 [::]:ssh [::]:* LISTEN<\/p>\n
tcp6 0 0 [::]:ipp [::]:* LISTEN<\/p>\n
tcp6 0 0 [::]:microsoft-ds [::]:* LISTEN<\/p>\n
tcp6 0 0 [::]:netbios-ssn [::]:* LISTEN<\/p>\n
udp 0 0 *:39505 *:*<\/p>\n
udp 0 0 *:ipp *:*<\/p>\n
udp 0 0 *:mdns *:*<\/p>\n
udp 0 0 *:mdns *:*<\/p>\n
Active UNIX domain sockets (only servers)<\/p>\n
Proto RefCnt Flags Type State I-Node Path<\/p>\n
unix 2 [ ACC ] STREAM LISTENING 12950 \/var\/run\/acpid.socket<\/p>\n
unix 2 [ ACC ] STREAM LISTENING 18259042 @atpl-com.canonical.Unity.Scope.rhythmbox.T516689809663571<\/p>\n
unix 2 [ ACC ] STREAM LISTENING 19096 \/run\/user\/1000\/keyring-n7CcyZ\/control<\/p>\n
unix 2 [ ACC ] STREAM LISTENING 22589 @\/tmp\/.ICE-unix\/3779<\/p>\n
unix 2 [ ACC ] STREAM LISTENING 21540 @\/tmp\/dbus-u6IauIGH5I<\/p>\n
To display open ports and established TCP connections, enter:<\/b><\/p>\n
Active Internet connections (servers and established)<\/p>\n
Proto Recv-Q Send-Q Local Address Foreign Address State<\/p>\n
tcp 0 0 0.0.0.0:1234 0.0.0.0:* LISTEN<\/p>\n
tcp 0 0 0.0.0.0:8084 0.0.0.0:* LISTEN<\/p>\n
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN<\/p>\n
tcp 0 0 0.0.0.0:631 0.0.0.0:* LISTEN<\/p>\n
tcp 0 0 0.0.0.0:445 0.0.0.0:* LISTEN<\/p>\n
tcp 0 0 0.0.0.0:7070 0.0.0.0:* LISTEN<\/p>\n
To display only open UDP ports try the following command:<\/b><\/p>\n
ravi@linuxforfreshers.com>>sudo netstat -vaun<\/p>\n
Active Internet connections (servers and established)<\/p>\n
Proto Recv-Q Send-Q Local Address Foreign Address State<\/p>\n
udp 0 0 0.0.0.0:39505 0.0.0.0:*<\/p>\n
udp 0 0 0.0.0.0:631 0.0.0.0:*<\/p>\n
\u25cf -l = only services which are listening on some port<\/p>\n
\u25cf -n = show port number, don’t try to resolve the service name<\/p>\n
\u25cf -p = name of the program<\/p>\n
To display the list of open ports, enter:<\/p>\n
To display all open files, use:<\/p>\n
To display all open IPv4 network files in use by the process whose PID is 10050, use:<\/p>\n
# lsof -iTCP -sTCP:LISTEN<\/b><\/p>\n
Quickest way to test if a TCP port is open (including any hardware firewalls you may have), is to type, from a remote computer (e.g. your desktop):<\/p>\n
telnet hostip port_number<\/b><\/p>\n
ravi@linuxforfreshers.com>>telnet 192.168.101.156 22<\/p>\n
Trying 192.168.101.156…<\/p>\n
Connected to 192.168.101.156<\/p>\n
Escape character is ‘^]’.<\/p>\n
ravi@linuxforfreshers.com>>telnet localhost 22<\/p>\n
ravi@linuxforfreshers.com>>ss -lntu<\/p>\n
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port<\/p>\n
tcp UNCONN 0 0 *:39505 *:*<\/p>\n
tcp UNCONN 0 0 *:631 *:*<\/p>\n
tcp UNCONN 0 0 *:5353 *:*<\/p>\n
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