The netstat utility displays open ports on a machine or the ports which are in use, it’ a utility but not a port scanning tool, so don’t get confused here 🙂
On widnows open command prompt and type
C:’WINDOWS>netstat -an |find /i “listening”
TCP 0.0.0.0:135 0.0.0.0:0 LISTENING
TCP 0.0.0.0:445 0.0.0.0:0 LISTENING
TCP 0.0.0.0:1025 0.0.0.0:0 LISTENING
TCP 0.0.0.0:1084 0.0.0.0:0 LISTENING
TCP 0.0.0.0:2094 0.0.0.0:0 LISTENING
TCP 0.0.0.0:3389 0.0.0.0:0 LISTENING
TCP 0.0.0.0:5000 0.0.0.0:0 LISTENINGYou can collect all the output in a file by redirecting it using the following command;
netstat -an |find /i “listening” > c:’openports.txt
In order to find out the ports to which your machine has established the connections you need to replace “listening” to “established”
You may get a similar output which would be as follows;
C:’WINDOWS>netstat -an |find /i “established”
TCP 192.168.0.100:1084 192.168.0.200:1026 ESTABLISHED
TCP 192.168.0.100:2094 192.168.0.200:1166 ESTABLISHED
TCP 192.168.0.100:2305 220.127.116.11:80 ESTABLISHED
TCP 192.168.0.100:2316 18.104.22.168:80 ESTABLISHED
TCP 192.168.0.100:2340 22.214.171.124:110 ESTABLISHED
Additional info about the netstat command;
NETSTAT [-a] [-b] [-e] [-n] [-o] [-p proto] [-r] [-s] [-v] [interval]
-a Displays all connections and listening ports.
-b Displays the executable involved in creating each connection or
listening port. In some cases well-known executables host
multiple independent components, and in these cases the
sequence of components involved in creating the connection
or listening port is displayed. In this case the executable
name is in  at the bottom, on top is the component it called,
and so forth until TCP/IP was reached. Note that this option
can be time-consuming and will fail unless you have sufficient
-e Displays Ethernet statistics. This may be combined with the -s
-n Displays addresses and port numbers in numerical form.
-o Displays the owning process ID associated with each connection.
-p proto Shows connections for the protocol specified by proto; proto
may be any of: TCP, UDP, TCPv6, or UDPv6. If used with the -s
option to display per-protocol statistics, proto may be any of:
IP, IPv6, ICMP, ICMPv6, TCP, TCPv6, UDP, or UDPv6.
-r Displays the routing table.
-s Displays per-protocol statistics. By default, statistics are
shown for IP, IPv6, ICMP, ICMPv6, TCP, TCPv6, UDP, and UDPv6;
the -p option may be used to specify a subset of the default.
-v When used in conjunction with -b, will display sequence of
components involved in creating the connection or listening
port for all executables.
interval Redisplays selected statistics, pausing interval seconds
between each display. Press CTRL+C to stop redisplaying
statistics. If omitted, netstat will print the current
configuration information once.