netstat
NETSTAT(8) Linux Programmer's Manual NETSTAT(8)
NAME
netstat - Print network connections, routing tables,
interface statistics, masquerade connections, and multi
cast memberships
SYNOPSIS
netstat [address_family_options] [--tcp|-t] [--udp|-u]
[--raw|-w] [--listening|-l] [--all|-a] [--numeric|-n]
[--numeric-hosts][--numeric-ports][--numeric-ports]
[--symbolic|-N] [--extend|-e[--extend|-e]] [--timers|-o]
[--program|-p] [--verbose|-v] [--continuous|-c]
netstat {--route|-r} [address_family_options]
[--extend|-e[--extend|-e]] [--verbose|-v] [--numeric|-n]
[--numeric-hosts][--numeric-ports][--numeric-ports]
[--continuous|-c]
netstat {--interfaces|-i} [iface] [--all|-a]
[--extend|-e[--extend|-e]] [--verbose|-v] [--program|-p]
[--numeric|-n] [--numeric-hosts][--numeric-
ports][--numeric-ports] [--continuous|-c]
netstat {--groups|-g} [--numeric|-n] [--numeric-
hosts][--numeric-ports][--numeric-ports] [--continuous|-c]
netstat {--masquerade|-M} [--extend|-e] [--numeric|-n]
[--numeric-hosts][--numeric-ports][--numeric-ports]
[--continuous|-c]
netstat {--statistics|-s} [--tcp|-t] [--udp|-u] [--raw|-w]
netstat {--version|-V}
netstat {--help|-h}
address_family_options:
[--protocol={inet,unix,ipx,ax25,netrom,ddp}[,...]]
[--unix|-x] [--inet|--ip] [--ax25] [--ipx] [--netrom]
[--ddp]
DESCRIPTION
Netstat prints information about the Linux networking sub
system. The type of information printed is controlled by
the first argument, as follows:
(none)
By default, netstat displays a list of open sockets. If
you don't specify any address families, then the active
sockets of all configured address families will be
printed.
--route , -r
Display the kernel routing tables.
--groups , -g
Display multicast group membership information for IPv4
and IPv6.
--interface=iface , -i
Display a table of all network interfaces, or the speci
fied iface).
--masquerade , -M
Display a list of masqueraded connections.
--statistics , -s
Display summary statistics for each protocol.
OPTIONS
--verbose , -v
Tell the user what is going on by being verbose. Espe
cially print some useful information about unconfigured
address families.
--numeric , -n
Show numerical addresses instead of trying to determine
symbolic host, port or user names.
--numeric-hosts
shows numerical host addresses but does not affect the
resolution of port or user names.
--numeric-ports
shows numerical port numbers but does not affect the reso
lution of host or user names.
--numeric-users
shows numerical user IDs but does not affect the resolu
tion of host or port names.
--protocol=family , -A
Specifies the address families (perhaps better described
as low level protocols) for which connections are to be
shown. family is a comma (',') separated list of address
family keywords like inet, unix, ipx, 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, --continuous
This will cause netstat to print the selected information
every second continuously.
-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. UP.
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 con
nected to this socket.
Send-Q
The count of bytes not acknowledged by the remote host.
Local Address
Address and port number of the local end of the socket.
Unless the --numeric (-n) option is specified, the socket
address is resolved to its canonical host name (FQDN), and
the port number is translated into the corresponding ser
vice name.
Foreign Address
Address and port number of the remote end of the socket.
Analogous to "Local Address."
State
The state of the socket. Since there are no states in raw
mode and usually no states used in UDP, this column may be
left blank. Normally 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
A connection request has been received from the
network.
FIN_WAIT1
The socket is closed, and the connection is shut
ting down.
FIN_WAIT2
Connection is closed, and the socket is waiting for
a shutdown from the remote end.
TIME_WAIT
The socket is waiting after close to handle packets
still in the network.
CLOSED The socket is not being used.
CLOSE_WAIT
The remote end has shut down, waiting for the
socket to close.
LAST_ACK
The remote end has shut down, and the socket is
closed. Waiting for acknowledgement.
LISTEN The socket is listening for incoming connections.
Such sockets are not included in the output unless
you specify the --listening (-l) or --all (-a)
option.
CLOSING
Both sockets are shut down but we still don't have
all our data sent.
UNKNOWN
The state of the socket is unknown.
User
The username or the user id (UID) of the owner of the
socket.
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.
Timer
(this needs to be written)
Active UNIX domain Sockets
Proto
The protocol (usually unix) used by the socket.
RefCnt
The reference count (i.e. attached processes via this
socket).
Flags
The flags displayed is SO_ACCEPTON (displayed as ACC),
SO_WAITDATA (W) or SO_NOSPACE (N). SO_ACCECPTON is used
on unconnected sockets if their corresponding processes
are waiting for a connect request. 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:
FREE The socket is not allocated
LISTENING
The socket is listening for a connection request.
Such sockets are only included in the output if you
specify the --listening (-l) or --all (-a) option.
CONNECTING
The socket is about to establish a connection.
CONNECTED
The socket is connected.
DISCONNECTING
The socket is disconnecting.
(empty)
The socket is not connected to another one.
UNKNOWN
This state should never happen.
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.
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
Starting with Linux release 2.2 netstat -i does not show
interface statistics for alias interfaces. To get per
alias interface counters you need to setup explicit rules
using the ipchains(8) command.
FILES
/etc/services -- The services translation file
/proc -- Mount point for the proc filesystem, which gives
access 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
SEE ALSO
route(8), ifconfig(8), ipchains(8), iptables(8), proc(5)
BUGS
Occasionally strange information may appear if a socket
changes as it is viewed. This is unlikely to occur.
AUTHORS
The netstat user interface was written by Fred Baumgarten
<dc6iq@insu1.etec.uni-karlsruhe.de> the man page basically
by Matt Welsh <mdw@tc.cornell.edu>. It was updated by Alan
Cox <Alan.Cox@linux.org> but could do with a bit more
work. It was updated again by Tuan Hoang <tqhoang@big
foot.com>.
The man page and the command included in the net-tools
package is totally rewritten by Bernd Eckenfels
<ecki@linux.de>.
net-tools 29 February 2000 1