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Name

netstat- Print network connections, routing tables, interface statis-
ticsstatistics, masquerade connections, and multicast memberships

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Synopsis

netstat[address_family_options] [--tcp|-t] [--udp|-u] [--raw|-w]
[--listening|-l] [--all|-a] [--numeric|-n] [--numeric-hosts]
[--numericports][--
numeric-ports] [--symbolic|-N] [--extend|-e[--extend|-e]]
[--timers|-o] [--program|-p] [--verbose|-v]
[--continuous|-c] [delay]

netstat {--route|-r} [address_family_options]
[--extend|-e[--extend|-e]] [--verbose|-v] [--numeric|-n] [--numerichosts–numerichosts]
[--
numeric-ports][--numeric-ports] [--continuous|-c] [delay]

netstat{--interfaces|-I|-i} [iface] [--all|-a] [--extend|-e] [--verbose|-
v] [--program|-p] [--numeric|-n] [--numeric-hosts]
[--numericports][--
numeric-ports] [--continuous|-c] [delay]

netstat {--groups|-g} [--numeric|-n] [--numeric-hosts][--numericports][--
numeric-ports] [--continuous|-c] [delay]

netstat{--masquerade|-M} [--extend|-e] [--numeric|-n] [--numerichosts][--
numeric-ports][--numeric-ports] [--continuous|-c] [delay]

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[--inet|--ip] [--ax25] [--ipx] [--netrom] [--ddp]

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–ddp]



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Description

Netstat prints information about the Linux networking subsystem. The
type The type of information printed is controlled by the first argument, as 
followsas follows:

(none)

By default, netstat displays a list of open sockets.If you don’t 
specify don’t specify any address families, then the active sockets of all configured 
address configured address families will be printed.

--route , -r

Display the kernel routing tables.

--groups , -g

Display multicast group membership information for IPv4 and IPv6.

--interfaces=iface , -I=iface , -i

Display a table of all network interfaces, or the specified iface.

--masquerade , -M

Display a list of masqueraded connections.

--route , -r

Display the kernel routing tables.

--statistics , -s

Display summary statistics for each protocol.

OPTIONS

--verbose , -v

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Options

-a, --all

Show both listening and non-listening sockets. With the --interfaces option, show interfaces that are not marked

-C

Print routing information from the route cache.

-c, --continuous

This will cause netstat to print the selected information every second continuously.

delay

Netstat will cycle printing through statistics every delay seconds.
UP.

-e, --extend

Display additional information. Use this option twice for maximum detail.

-F

Print routing information from the FIB. (This is the default.)

-l, --listening

Show only listening sockets. (These are omitted by default.)

--numeric , -n

Show numerical addresses instead of trying to determine symbolic host,
port  port or user names.

--numeric-hosts

shows numerical host addresses but does not affect the resolution of 
port of port or user names.

--numeric-ports

shows numerical port numbers but does not affect the resolution of
host or of host or user names.

--numeric-users

shows numerical user IDs but does not affect the resolution of host or
port namesor port names.

-o, --timers

Include information related to networking timers.

-p, --program

Show the PID and name of the program to which each socket belongs.

--protocol=family , -A

Specifies the address families (perhaps better described as low level
protocolslevel protocols) for which connections are to be shown. family is a comma 
(’,’) separated list of address family keywords like inet, unix, ipx,
 ax25  ax25, netrom, and ddp. This has the same effect as using the --inet,
 --unix (-x), --ipx, --ax25, --netrom, and --ddp options. 

The address family inet includes raw, udp and tcp protocol sockets.

-c, T --continuous

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notrim

Stop trimming long addresses.

-e, --extend

Display additional information. Use this option twice for maximum detail.

-o, --timers

Include information related to networking timers.

-p, --program

Show the PID and name of the program to which each socket belongs.

-l, --listening

Show only listening sockets. (These are omitted by default.)

-a, --all

Show both listening and non-listening sockets. With the --interfaces
option, show interfaces that are not marked

-F

Print routing information from the FIB.(This is the default.)

-C

Print routing information from the route cache.

--verbose , -v

Tell the user what is going on by being verbose. Especially print some useful information about unconfigured address families.

-Z --context

If SELinux enabled print SELinux context.

-T --notrim

Stop trimming long addresses.

delay

Netstat will cycle printing through statisticsevery delay seconds.
UP.

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Output

Active Internet connections (TCP, UDP, raw)

Proto

The protocol (tcp, udp, raw) used by the socket.

Recv-Q

The count of bytes not copied by the user program connected to this socket.

Send-Q

The count of bytes not acknowledged by the remote host.Foreign Address

Address and port number of the remote end of the socket. Analogous to "Local Address."

Local Address

Address and port number of the local end of the socket. Unless

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the  --numeric (-n) option is specified, the socket address is resolved

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to its canonical host name (FQDN), and the port number is translated

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into the corresponding service name.

Foreign Address

Address and port number of the remote end of the socket. Analogous to
"Local Address."PID/Program name

Slash-separated pair of the process id (PID) and process name of the process that owns the socket. --program causes this column to be included. You will also need superuser privileges to see this information on sockets you don’t own.This identification information is not yet available for IPX sockets.

Proto

The protocol (tcp, udp, raw) used by the socket.

Recv-Q

The count of bytes not copied by the user program connected to this socket.

Send-Q

The count of bytes not acknowledged by the remote host.

State

The state of the socket. Since there are no states in raw mode and

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usually no states used in UDP, this column may be left blank. Normally

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this can be one of several values:

ESTABLISHED

The socket has an established connection.

SYN_SENT

The socket is actively attempting to establish a connection.

SYN_RECV

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CLOSED   The socket is not being used.

CLOSE_WAIT

The remote end has shut down, waiting for the socket to close.

CLOSING

Both sockets are shut down but we still don’t have all our data sent.

ESTABLISHED

The socket has an established connection.

FIN_WAIT1

The socket is closed, and the connection is shutting down.

FIN_WAIT2

Connection is closed, and the socket is waiting for a

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shutdown from the remote end

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TIME_WAIT

The socket is waiting after close to handle packets still in the
network.

CLOSED   The socket is not being used.

CLOSE_WAIT

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.

LAST_ACK

The remote end has shut down, and the socket is closed.

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Waiting for acknowledgement.

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LISTEN    The socket is listening for incoming connections. Such sockets

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are not included in the output unless you specify the --listen

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ing (-l) or --all (-

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CLOSING

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          a) option.

SYN_RECV

A connection request has been received from the network.

SYN_SENT

The socket is actively attempting to establish a connection.

TIME_WAIT

The socket is waiting after close to handle packets still in the network.

UNKNOWN

The state of the socket is unknown.

Timer

(this needs to be written)

User

The username or the user id (UID) of the owner of the socket.

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PID/Program name

Slash-separated pair of the process id (PID) and process name of the 
process that owns the socket. --program causes this column to be 
included. You will also need superuser privileges to see this info-
rmation on sockets you don’t own.This identification information is not 
yet available for IPX sockets.

Timer

Active UNIX domain Sockets

Active IPX sockets

(this needs to be done by somebody who knows it)

Active NET/ROM sockets

(this needs to be

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done by somebody who knows it)

Active

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Proto

The protocol (usually unix) used by the socket.

RefCnt

The reference count (i.e. attached processes via this socket).AX.25 sockets

(this needs to be done by somebody who knows it)

Flags

The flags displayed is SO_ACCEPTON (displayed as ACC), SO_WAITDATA (W)

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or SO_NOSPACE(N). SO_ACCECPTON

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is used on unconnected sockets

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if their corresponding processes are waiting for

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a connect request.

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The other flags are not of normal interest.

Type

There are several types of socket access:

SOCK_DGRAM

The socket is used in Datagram (connectionless) mode.

SOCK_STREAM

This is a stream (connection) socket.

SOCK_RAW

The socket is used as a raw socket.

SOCK_RDM

This one serves reliably-delivered messages.

SOCK_SEQPACKET

This is a sequential packet socket.

SOCK_PACKET

Raw interface access socket.

UNKNOWN

Who ever knows what the future will bring us - just fill in here
:-)

State

This field will contain one of the following Keywords:Path

This is the path name as which the corresponding processes attached to the socket.

PID/Program name

Process ID (PID) and process name of the process that has the socket open. More info available in Active Internet connections section written above.

Proto

The protocol (usually unix) used by the socket.

RefCnt

The reference count (i.e. attached processes via this socket).

State

This field will contain one of the following Keywords:

CONNECTED

The socket is connected.

CONNECTING

The socket is about to establish a connection.

DISCONNECTING

The socket is disconnecting.

(empty)

The socket is not connected to another one.

FREE The socket is not allocated

LISTENING

The socket is listening for a connection request. Such

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sockets are only included in the output if you specify the --listening 

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(-l) or --all (-a) option.

UNKNOWN

This state should never happen.

CONNECTING

The socket is about to establish a connection.

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Type

There are several types of socket access:

SOCK_DGRAM

The socket is

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used in Datagram (connection less) mode.

DISCONNECTING

The socket is disconnecting.

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SOCK_PACKET

Raw interface access socket.

SOCK_RAW

The socket is

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used as a raw socket.

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SOCK_RDM

This

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PID/Program name

Process ID (PID) and process name of the process that has the socket
open. More info available in Active Internet connections section writ-
ten above.

Path

This is the path name as which the corresponding processes attached to
the socket.

Active IPX sockets

(this needs to be done by somebody who knows it)

Active NET/ROM sockets

(this needs to be done by somebody who knows it)

Active AX.25 sockets

(this needs to be done by somebody who knows it)

NOTES

one serves reliably-delivered messages.

SOCK_STREAM

This is a stream (connection) socket.

SOCK_SEQPACKET

This is a sequential packet socket.

UNKNOWN

Who ever knows what the future will bring us - just fill in here :-)

Notes

Starting with Linux release 2.2 netstat -i does not show interface
statistics for alias interfaces. To get per alias interface counters
you counters you need to setup explicit rules using the ipchains (8) command.

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Files

/etc/services -- The services translation file

/proc -- Mount pointfor point for the proc filesystemfile system, which gives access to kernel
status to kernel status information via the following files.

/proc/net/dev -- device information

/proc/net/raw -- raw socket information

/proc/net/tcp -- TCP socket information

/proc/net/udp -- UDP socket information

/proc/net/igmp -- IGMP multicast information

/proc/net/unix -- Unix domain socket information

/proc/net/ipx -- IPX socket information

/proc/net/ax25 -- AX25 socket information

/proc/net/appletalk -- DDP (appletalk) socket information

/proc/net/nr -- NET/ROM socket information

/proc/net/route -- IP routing information

/proc/net/ax25_route -- AX25 routing information

/proc/net/ipx_route -- IPX routing information

/proc/net/nr_nodes -- NET/ROM nodelist

/proc/net/nr_neigh -- NET/ROM neighbours

/proc/net/ip_masquerade -- masqueraded connections

/proc/net/snmp -- statistics

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See Also

ss(8),ip(8)

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Bugs

Occasionally strange information may appear if a socket changes as it
is it is viewed. This is unlikely to occur.

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Authors

The netstat user interface waswritten by Fred Baumgarten
 <dc6iq@Baumgarten  <dc6iq@insu1.etec.uni-karlsruhe.de> theman > the man page basically by Matt 
Welsh<mdw@Matt Welsh<mdw@tc.cornell.edu>. It was updated by Alan Cox 
<Cox <Alan.Cox@linux.org> but could do with a bit more work.It was updated 
again updated again by Tuan Hoang <tqhoang@bigfoot.com>.
The man page and the command included command  included in the net-tools package is 
totally rewritten by Bernd is totally rewritten by Bernd Eckenfels <ecki@linux.de>.