.TH NETSTAT 1 "18 October 1982"
.UC 4
.SH NAME
netstat \- show network status
.SH SYNOPSIS
.B netstat
[ 
.B \-Aahimnrs
] [
.B \-p
.I protocol 
] [
.B \-a
] [
.I interval
] [
.I system
] [
.I core
]
.SH DESCRIPTION
The
.I netstat 
command symbolically displays the contents of various network-related
data structures.  The options have the following meaning:
.TP 
.B \-A
show the address of any associated protocol control blocks; used
for debugging
.TP
.B \-a
show the state of all sockets; normally sockets used by
server processes are not shown
.TP
.B \-h
show the state of the IMP host table
.TP
.B \-i
show the state of interfaces which have been auto-configured
(interfaces statically configured into a system, but not
located at boot time are not shown)
.TP
.B \-m
show statistics recorded by the memory management routines
(the network manages a ``private share'' of memory)
.TP
.B \-n
show network addresses as numbers (normally 
.I netstat
interprets addresses and attempts to display them
symbolically)
.TP
.BI \-p " proto"
show the state of sockets utilizing protocol
.IR proto ;
the protocol is specified symbolically, and may be any
protocol listed in the file
.IR /etc/protocols .
.TP
.B \-s
show per-protocol statistics
.TP
.B \-r
show the routing tables
.PP
The arguments, 
.I system
and
.I core
allow substitutes for the defaults ``/vmunix'' and ``/dev/kmem''.
.PP
If an 
.I interval
is specified,
.I netstat
will continuously display the information regarding packet
traffic on the configured network interfaces, pausing
.I interval
seconds before refreshing the screen.
.PP
There are a number of display formats, depending on the information
presented.  The default display, for active sockets, shows the local
and remote addresses, send and receive queue sizes (in bytes), protocol,
and, optionally, the internal state of the protocol.
.PP
Address formats are of the form ``host.port'' or ``network.port''
if a socket's address specifies a network but no specific host address.
When known the host and network addresses are displayed symbolically
according to the data bases
.I /etc/hosts
and
.IR /etc/networks ,
respectively.  If a symbolic name for an address is unknown, or if
the 
.B \-n
option is specified, the address is printed in the Internet ``dot format'';
refer to 
.IR inet (3N)
for more information regarding this format.
Unspecified,
or ``wildcard'', addresses and ports appear as ``*''.  
.PP
The interface display provides a table of cumulative
statistics regarding packets transferred, errors, and collisions.
The network address (currently Internet specific) of the interface
and the maximum transmission unit (``mtu'') are also displayed.
.PP
The routing table display indicates the available routes and
their status.  Each route consists of a destination host or network
and a gateway to use in forwarding packets.  The flags field shows
the state of the route (``U'' if ``up''), and whether the route
is to a gateway (``G'').  Direct routes are created for each
interface attached to the local host.  The refcnt field gives the
current number of active uses of the route.  Connection oriented
protocols normally hold on to a single route for the duration of
a connection while connectionless protocols obtain a route then
discard it.  The use field provides a count of the number of packets
sent using that route.  The interface entry indicates the network
interface utilized for the route.
.PP
When 
.I netstat
is invoked with an
.I interval
argument, it displays a running count of statistics related to
network interfaces.  This display consists of a column summarizing
information for all interfaces, and a column for the interface with
the most traffic since the system was last rebooted.  The first
line of each screen of information contains a summary since the
system was last rebooted.  Subsequent lines of output show values
accumulated over the preceding interval.
.SH SEE ALSO
iostat(1),
vmstat(1),
hosts(5),
networks(5),
protocols(5),
services(5),
trpt(8C)
.SH BUGS
The notion of errors is ill-defined.  Collisions mean
something else for the IMP.