NETSTAT(1) MachTen Programmer’s Manual NETSTAT(1)

NAME
netstat - show network status

SYNOPSIS
netstat [ -Aan ] [ -f address_family ] [ system ] [ core ]
netstat [ -himnrs ] [ -f address_family ] [ system ] [
core ]
netstat [ -n ] [ -I interface ] interval [ system ] [ core
]
netstat [ -p protocol ] [ system ] [ core ]

DESCRIPTION
The netstat command symbolically displays the contents of
various network-related data structures. There are a num-
ber of output formats, depending on the options for the
information presented. The first form of the command dis-
plays a list of active sockets for each protocol. The
second form presents the contents of one of the other net-
work data structures according to the option selected.
Using the third form, with an interval specified, netstat
will continuously display the information regarding packet
traffic on the configured network interfaces. The fourth
form displays statistics about the named protocol.

The options have the following meaning:

-A With the default display, show the address of any pro-
tocol control blocks associated with sockets; used for
debugging.

-a With the default display, show the state of all sock-
ets; normally sockets used by server processes are not
shown. -d With either interface display (option -i or
an interval, as described below), show the number of
dropped packets.

-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).

-I interface
Show information only about this interface; used with
an interval as described below.

-m Show statistics recorded by the memory management rou-
tines (the network manages a private pool of memory
buffers).

-n Show network addresses as numbers (normally netstat
interprets addresses and attempts to display them sym-
bolically). This option may be used with any of the
display formats.

-p protocol
Show statistics about protocol, which is either a
well-known name for a protocol or an alias for it.
Some protocol names and aliases are listed in the file
/etc/protocols. A null response typically means that
there are no interesting numbers to report. The pro-
gram will complain if protocol is unknown or if there
is no statistics routine for it.

-s Show per-protocol statistics.

-r Show the routing tables. When -s is also present,
show routing statistics instead.

-f address_family
Limit statistics or address control block reports to
those of the specified address family. The following
address families are recognized: inet, for AF_INET,
ns, for AF_NS, and unix, for AF_UNIX.

The arguments, system and core allow substitutes for the
defaults ‘‘/vmunix’’ and ‘‘/dev/kmem’’.

The default display, for active sockets, shows the local
and remote addresses, send and receive queue sizes (in
bytes), protocol, and the internal state of the protocol.
Address formats are of the form ‘‘host.port’’ or ‘‘net-
work.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 /etc/hosts and /etc/networks, respectively. If a
symbolic name for an address is unknown, or if the -n
option is specified, the address is printed numerically,
according to the address family. For more information
regarding the Internet ‘‘dot format,’’ refer to inet(3).
Unspecified, or ‘‘wildcard’’, addresses and ports appear
as ‘‘*’’.

The interface display provides a table of cumulative
statistics regarding packets transferred, errors, and col-
lisions. The network addresses of the interface and the
maximum transmission unit (‘‘mtu’’) are also displayed.

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 pack-
ets. The flags field shows the state of the route (‘‘U’’
if ‘‘up’’), whether the route is to a gateway (‘‘G’’),
whether the route was created dynamically by a redirect
(‘‘D’’), and whether the route has been modified by a
redirect (‘‘M’’). Direct routes are created for each
interface attached to the local host; the gateway field
for such entries shows the address of the outgoing inter-
face. 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 while send-
ing to the same destination. 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.

When netstat is invoked with an interval argument, it dis-
plays a running count of statistics related to network
interfaces. This display consists of a column for the
primary interface (the first interface found during auto-
configuration) and a column summarizing information for
all interfaces. The primary interface may be replaced
with another interface with the -I option. 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.

SEE ALSO
iostat(1), vm_stat(1)*, hosts(5), networks(5), proto-
cols(5), services(5), trpt(8)*

BUGS
The notion of errors is ill-defined.

__________
* Not currently supported under MachTen

MachTen May 14, 1988 3