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Manpage of NETSTAT
NETSTAT
Section: Linux Programmer's Manual (8)
Updated: 19 May 1997
Index
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NAME
netstat - Display network connections, routing tables, interface statistics and masquerade connections.
SYNOPSIS
netstat
[-venaoc]
[--tcp|-t]
[--udp|-u]
[--raw|-w]
[--unix|-u]
[--inet|--ip]
[--ax25]
[--ipx]
[--netrom]
netstat
[-veenc]
[--inet]
[--ipx]
[--netrom]
[--ddp]
[--ax25]
{--route|-r}
netstat
[-veenac]
{--interfaces|-i}
[iface]
netstat
[-enc]
{--masquerade|-M}
netstat
{--statistics|-s}
netstat
{-V|--version}
{-h|--help}
DESCRIPTION
Netstat
displays information of the Linux networking subsystem.
(no option)
You can view the
status of network connections by listing the open sockets. This is the
default operation: If you don't specify any address families, then the
active sockets of all configured address families will be printed. With
-e
you get some additional informations (userid). With the
-v
switch you can make netstat complain about known address families which are
not supported by the kernel. The
-o
option displays some additional information on networking timers.
-a
print all sockets, including the listening server sockets. The address
family
inet
will display raw, udp and tcp sockets.
-r, --route
With the
-r, --route
option, you get the kernel routing tables in the same format as
route -e
use.
netstat -er
will use the output format of
route.
Please see
route(8)
for details.
-i, --interface iface
If you use the
-i, --interfaces
option, a table of all (or the specified
iface)
networking interfaces will be printed. The output uses the
ifconfig -e
format, and is described in
ifconfig(8).
netstat -ei
will print a table or a single interface entry just like
ifconfig
does. With the
-a
switch, you can include interfaces which are not configured (i.e. don't have
the
U=UP
flag set).
-M, --masquerade
A list of all masqueraded sessions can be viewed, too. With the
-e
switch you can include some more informations about sequenze numbering and
deltas, caused by data rewrites on FTP sessions (PORT
command). Masquerade support is used to hide hosts with unofficial network
addresses from the outside world, as described in
ipfw(4),ipfwadm(8) and ipfw(8).
-s, --statistics
Displays statistics about the networking subsystem of the Linux Kernel which
are read from
/proc/net/snmp
OPTIONS
-v, --verbose
Tell the user what is going on by being verbose. Especially print some
usefull informations about unconfigured address families.
-n, --numeric
shows numerical addresses instead of trying to determine symbolic host, port
or user names.
-A, --af family
use a different method to set the address families.
family
is a comma (',') seperated list of address family keywords like
inet,
unix,
ipx,
ax25,
netrom
and
ddp.
This is has the same effect as using the long options
--inet,
--unix,
--ipx,
--ax25,
--netrom
and
--ddp.
-c, --continous
This will cause
netstat
to print the selected table every second continously on the screen until you
interrupt it.
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 acknoledged by the remote host.
Local Address
The local address (local hostname) and port number of the socket. Unless
the
-n
switch is given, the socket address is resolved to its canonical
hostname, and the port number is translated into the corresponding service
name.
Foreign Address
The remote address (remote hostname) and port number of he socket. As
with the local address:port, the
-n
switch turns off hostname and service name resolution.
State
The state of the socket. Since there are no states in RAW and usually no
states used in UDP, this row 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
-
The connection is being initialized.
- FIN_WAIT1
-
The socket is closed, and the connection is shutting 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 for remote shutdown retransmission.
- 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 shut down, and the socket is closed. Waiting for
acknowledgement.
- LISTEN
-
The socket is listening for incoming connections. Those sockets are only
displayed if the
-a,--listening
switch is set.
- 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 name or the UID of the owner of the socket.
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. Those sockets are only
displayed if the
-a,--listening
switch is set.
- 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.
Path
This displays 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)
FILES
/etc/services
-- The services translation file
/proc/net/dev
-- devices information
/proc/net/snmp
-- networking statistics
/proc/net/raw
-- RAW socket information
/proc/net/tcp
-- TCP socket information
/proc/net/udp
-- UDP socket information
/proc/net/unix
-- Unix domain socket information
/proc/net/ipx
-- IPX socket information
/proc/net/ax25
-- AX25 socket information
/proc/net/appeltalk
-- DDP (appeltalk) socket information
/proc/net/nr
-- NET/ROM socket information
/proc/net/route
-- Kernel IP routing information
/proc/net/ax25_route
-- Kernel AX25 routing information
/proc/net/ipx_route
-- Kernel IPX routing information
/proc/net/nr_nodes
-- Kernel NET/ROM nodelist
/proc/net/nr_neigh
-- Kernel NET/ROM neighbours
/proc/net/ip_masquerade
-- Kernel masqueraded connections
SEE ALSO
route(8),
ifconfig(8),
ipfw(4),
ipfw(8),
ipfwadm(8)
BUGS
Occasionally strange information may appear if a socket changes
as it is viewed. This is unlikely to occur.
The
netstat -i
options is described as it should work after some code cleanup of the BETA
release of the net-tools package.
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.
The man page and the command included in the net-tools
package is totally rewritten from Bernd Eckenfels
<ecki@linux.de>.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- (no option)
-
- -r, --route
-
- -i, --interface iface
-
- -M, --masquerade
-
- -s, --statistics
-
- OPTIONS
-
- -v, --verbose
-
- -n, --numeric
-
- -A, --af family
-
- -c, --continous
-
- OUTPUT
-
- Active Internet connections (TCP, UDP, RAW)
-
- Proto
-
- Recv-Q
-
- Send-Q
-
- Local Address
-
- Foreign Address
-
- State
-
- User
-
- Timer
-
- Active UNIX domain Sockets
-
- Proto
-
- RefCnt
-
- Flags
-
- Type
-
- State
-
- Path
-
- Active IPX sockets
-
- Active NET/ROM sockets
-
- Active AX.25 sockets
-
- FILES
-
- SEE ALSO
-
- BUGS
-
- AUTHORS
-
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Time: 12:16:39 GMT, November 04, 1999