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NETSTAT (8)

Display network connections, routing tables, interface statistics, masquerade connections, netlink messages, and multicast memberships

SYNOPSIS

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 }

DESCRIPTION

Netstat

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.

The -a , --all option will print information about all sockets, including the listening server sockets.

The -l , --listening option will print information about listening server sockets only.

The -e , --extend option prints some additional information (e.g. user id and inode of the connection).

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).

The -v , --verbose switch makes netstat complain about known address families which are not supported by the kernel.

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.

With the -g , --groups option, IGMP multicast group membership information for IPv4 and IPv6 is displayed.

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).

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).

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).

OPTIONS

shows numerical addresses instead of trying to determine symbolic host, port or user names.

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.

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.

This will cause netstat to print the selected table every second continously on the screen until you interrupt it.

OUTPUT

The protocol (tcp, udp, raw) used by the socket.

The count of bytes not copied by the user program connected to this socket.

The count of bytes not acknoledged by the remote host.

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.

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.

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:

-a , --listening

The name or the UID of the owner of the socket.

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.

(this needs to be written)

The protocol (usually unix) used by the socket.

The reference count (i.e. attached processes via this socket).

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.

There are several types of socket access:

This field will contain one of the following Keywords:

-a , --listening

PID and process name of the program holding this socket. More info available in Active Internet connections section written above.

This displays the path name as which the corresponding processes attached to the socket.

(this needs to be done by somebody who knows it)

NOTES

ipchains(8)

FILES

/etc/services

/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

BUGS

netstat -i