Computer Network:netstat program,netstat command

Object:  Study netstat program. Run netstat command with various option on command prompt.

(1) –a   (2) –e   (3) –n  (4) –s  (5) –p  (6) –r  

The netstat command is used to show network status.Traditionally, it is used more for problem determination than for performance measurement. However,the netstat command can be used to determine the amount of traffic on the network to ascertain whether performance problems are due to network congestion. The netstat command displays information regarding traffic on the configured network interfaces, such as the following:

- The address of any protocol control blocks associated with the sockets and the state of all sockets

-The number of packets received, transmitted, and dropped in the communications  subsystem

-Cumulative statistics per interface

-Routes and their status

Syntax

NETSTAT [-a] [-e] [-n] [-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.
-p	proto Shows connections for the protocol specified by proto; proto may be TCP or UDP. If used with the -s option to display per-protocol statistics, proto may be TCP, UDP, or IP.
-r	Displays the routing table.
-s	Displays per-protocol statistics. By default, statistics are shown for TCP, UDP and IP; 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.

Output :