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GNU/Linux |
RedHat 6.2(Zoot) |
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netstat(8) |
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netstat − Display network connections, routing tables, interface statistics, masquerade connections, netlink messages, and multicast memberships
netstat [−venaocs] [−−tcp|−t] [−−udp|−u] [−−raw|−w] [−−groups|−g] [−−unix|−x] [−−inet|−−ip] [−−ax25] [−−ipx] [−−netrom]
netstat [−venc] [−−inet] [−−ipx] [−−netrom] [−−ddp] [−−ax25] {−−route|−r}
netstat [−venpac] {−−interfaces|−i} [iface]
netstat [−enc] {−−masquerade|−M}
netstat [−cn] {−−netlink|−L}
netstat {−V|−−version} {−h|−−help}
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.
The address family inet will display raw, udp and tcp
sockets.
−a,
−−all
The −a, −−all option will
print information about all sockets, including the listening
server sockets.
−l,
−−listening
The −l, −−listening option
will print information about listening server sockets
only.
−e,
−−extend
The −e, −−extend option
prints some additional information (e.g. user id and inode
of the connection).
−p,
−−programs
The −p, −−programs option
displays additional information about the program that is
using the socket (e.g. process id and the name of the
program).
−v,
−−verbose
The −v, −−verbose switch
makes netstat complain about known address families which
are not supported by the kernel.
−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.
−g,
−−groups
With the −g, −−groups
option, IGMP multicast group membership information for IPv4
and IPv6 is displayed.
−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).
−L,
−−netlink
Recent kernels have a kernel/user communication support
called netlink. You can get messages about creation or
deletion of interfaces or routes from /dev/route
(36,0).
−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.
−p,
−−programs
displays process name and PID of the owner of each socket it
dumps. You have to be the owner of such process to have all
it’s sockets matched to it or generally root
user will see all the necessary information in place.
−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.
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
A connection request has been received from the network.
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 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 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.
PID/Program
name
Slash-separated pair of the PID and process name of the
program holding this socket. Option -p enables
display of this column. You will also need root
privileges as you have to have access rights to process to
be able to see the program’s sockets matched up to it.
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. 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.
PID/Program
name
PID and process name of the program holding this socket.
More info available in Active Internet connections
section written above.
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)
Since kernel release 2.2 netstat -i does not display interface statistics for alias interfaces anymore. To get per alias interface counters you need to setup explicit rules using the ipchains(8) command.
/etc/services -- The services translation file
/proc/net/dev -- devices 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 -- 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
route(8), ifconfig(8), ipfw(4), ipfw(8), ipfwadm(8) ipchains(8)
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.
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@bigfoot.com>.
The man page and the command included in the net-tools
package is totally rewritten from Bernd Eckenfels
<ecki@linux.de>.
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netstat(8) | |