netstat(1M) (TCP/IP) netstat(1M)
NAME
netstat - show network status
SYNOPSIS
netstat [ -aAn ] [ -f addr_family ] [ system ] [ core ]
netstat [ -n ] [ -s ] [ -h | -i | -m | -r ] [ -f addr_family ] [
system ] [ core ]
netstat [ -n ] [ -I interface ] interval [ system ] [ core ]
DESCRIPTION
netstat displays the contents of various network-related data
structures in various formats, depending on the options you select.
The first form of the command displays a list of active sockets for
each protocol. The second form selects one from among various other
network data structures. The third form displays running statistics
of packet traffic on configured network interfaces; the interval
argument indicates the number of seconds in which to gather
statistics between displays.
The default value for the system argument is /stand/unix; for core,
the default is /dev/kmem.
The following options are available:
-a Show the state of all sockets; normally sockets used by server
processes are not shown.
-A Show the address of any protocol control blocks associated with
sockets; used for debugging.
-h Show the state of the IMP host table. This does not work in an
environment where the IMP host tables do not exist.
-i Show the state of interfaces that have been auto-configured.
Interfaces that are statically configured into a system, but
not located at boot time, are not shown.
-m Show the statistics recorded by management routines for the
network's private buffer pool.
-n Show network addresses as numbers. netstat normally displays
addresses as symbols. This option may be used with any of the
display formats.
-r Show the routing tables. When used with the -s option, show
routing statistics instead.
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-s Show per-protocol statistics. When used with the -r option,
show routing statistics.
-f addr_family
Limit statistics or address control block reports to those of
the specified addr_family, which can be one of:
inet For the AF_INET address family, or
unix For the AF_UNIX family.
-I interface
Highlight information about the indicated interface in a
separate column; the default (for the third form of the
command) is the interface with the most traffic since the
system was last rebooted. interface can be any valid interface
listed in the system configuration file, such as emd1 or lo0.
DISPLAYS
Active Sockets (First Form)
The display for each active socket shows the local and remote
address, the send and receive queue sizes (in bytes), the protocol,
and the internal state of the protocol.
The symbolic format normally used to display socket addresses is
either:
hostname.port
when the name of the host is specified, or:
network.port
if a socket address specifies a network but no specific host. Each
hostname and network is shown according to its entry in the
/etc/hosts or the /etc/networks file, as appropriate.
If the network or hostname for an address is not known (or if the -n
option is specified), the numerical network address is shown.
Unspecified, or wildcard, addresses and ports appear as *. For more
information regarding the Internet naming conventions, refer to
inet(7).
TCP Sockets
The possible state values for TCP sockets are as follows:
CLOSED Closed. The socket is not being used.
LISTEN Listening for incoming connections.
SYNSENT Actively trying to establish connection.
SYNRECEIVED Initial synchronization of the connection
under way.
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netstat(1M) (TCP/IP) netstat(1M)
ESTABLISHED Connection has been established.
CLOSEWAIT Remote shut down; waiting for the socket to
close.
FINWAIT1 Socket closed; shutting down connection.
CLOSING Closed, then remote shutdown; awaiting
acknowledgement.
LASTACK Remote shut down, then closed; awaiting
acknowledgement.
FINWAIT2 Socket closed; waiting for shutdown from
remote.
TIMEWAIT Wait after close for remote shutdown
retransmission.
Network Data Structures (Second Form)
The form of the display depends upon which of the -m, -i, -h or -r,
options you select. If you specify more than one of these options,
netstat selects one in the order listed here.
Routing Table Display
The routing table display lists the available routes and the status
of each. Each route consists of a destination host or network, and a
gateway to use in forwarding packets. The flags column shows the
status of the route (U if up), whether the route is to a gateway (G),
and whether the route was created dynamically by a redirect (D).
Direct routes are created for each interface attached to the local
host; the gateway field for such entries shows the address of the
outgoing interface.
The refcnt column gives the current number of active uses per route.
Connection-oriented protocols normally hold on to a single route for
the duration of a connection, whereas connectionless protocols obtain
a route while sending to the same destination.
The use column displays the number of packets sent per route.
The interface entry indicates the network interface utilized for the
route.
Cumulative Traffic Statistics (Third Form)
When the interval argument is given, netstat displays a table of
cumulative statistics regarding packets transferred, errors and
collisions, the network addresses for the interface, and the maximum
transmission unit (mtu). The first line of data displayed, and every
24th line thereafter, contains cumulative statistics from the time
the system was last rebooted. Each subsequent line shows incremental
statistics for the interval (specified on the command line) since the
previous display.
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SEE ALSO
iostat(1M), trpt(1M), vmstat(1M), hosts(4), networks(4),
protocols(4), services(4).
NOTES
The notion of errors is ill-defined.
The kernel's tables can change while netstat is examining them,
creating incorrect or partial displays.
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