what is the use of netstat?give example?

Answer 1

netstat is a commandline tool that displays a list of the active connections a computer currently has, both incoming and outgoing. It is available on Unix and Unix-like operating systems, as well as Windows (running the NT kernel).
NETSTAT.exe

Display current TCP/IP network connections and protocol statistics.

Syntax
NETSTAT [options] [-p protocol] [interval]
Key -a Display all connections and listening ports.
-e Display Ethernet statistics. (may be combined with -s)
-n Display addresses and port numbers in numerical form.
-r Display the routing table.

-o Display the owning process ID associated with each connection.
(XP only)

-p protocol Show only connections for the protocol specified;
may be either: TCP or UDP.
Windows 2K/XP also allow: TCPv6 or UDPv6.
If used with the -s option then the following protocols
may also be specified: IP, IPv6, ICMP,or ICMPv6.

-s Display per-protocol statistics. By default, statistics are
shown for IP, ICMP, TCP and UDP.
Windows 2K/XP will also display: IPv6, ICMPv6, TCPv6 and UDPv6
The -p option may be used to specify a subset of the default.

interval Redisplay statistics, pausing interval seconds between
each display. (default=once only) Press CTRL+C to stop.

Answer 2

Once you're on the network, you can do a command called NetStat - Network Status - and it lists all the connections to that machine. for more details refer this site: http://www.ss64.com/nt/netstat.html

Answer 3

netstat tells you what tcp and udp ports are in use on that machine

for example, netstat tells me that yahoo answers is currently using port tcp 4077 on my pc