The netstat command is used to display current connections to the end system. This can be useful
in a troubleshooting scenario to assist in the verification of connectivity. In addition to the IP
addresses of the connections, the netstat command also shows the port the connections are
using. The Windows NT/2000/XP options and sample output of the command are shown here:
C:\>netstat /?
Displays protocol statistics and current TCP/IP network connections.
NETSTAT [-a] [-e] [-n] [-o] [-s] [-p proto] [-r] [interval]
-a Displays all connections and listening ports.
-e Displays Ethernet statistics. This may be combined with the -s
option.
-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.
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.
C:\>netstat -n
Active Connections
Proto Local Address Foreign Address State
TCP 10.12.1.11:3718 10.215.198.192:80 ESTABLISHED
TCP 10.12.1.11:3719 10.215.198.153:80 ESTABLISHED
TCP 10.12.1.11:3722 10.215.198.6:80 ESTABLISHED
TCP 10.12.1.11:3724 10.12.1.100:139 ESTABLISHED
TCP 10.12.1.11:3726 10.255.37.1:23 ESTABLISHED
The Unix version of the command is very similar to the Windows version. Its options and
sample output are as follows:
unix1% netstat -help
usage: netstat [-adgimnprsDMv] [-I interface] [interval]
unix1% netstat -n
TCP
Local Address Remote Address Swind Send-Q Rwind Recv-Q State
----------------- ----------------- ----- ------ ----- ------ ------
10.4.132.58.32891 10.4.132.58.162 57344 0 57344 0 ESTAB
10.4.132.58.162 10.4.132.58.32891 57344 0 57344 0 ESTAB
10.4.132.58.53074 10.4.128.10.1960 24820 0 8760 0 ESTAB
10.4.132.58.38090 10.104.108.13.1960 62780 0 8760 0 ESTAB
...
...