netstat



NETSTAT(8)                 Linux Programmer’s Manual                NETSTAT(8)




NAME

       netstat  - Print network connections, routing tables, interface statis-
       tics, masquerade connections, and multicast memberships



SYNOPSIS

       netstat  [address_family_options]  [--tcp|-t]   [--udp|-u]   [--raw|-w]
       [--listening|-l] [--all|-a] [--numeric|-n] [--numeric-hosts][--numeric-
       ports][--numeric-ports]   [--symbolic|-N]    [--extend|-e[--extend|-e]]
       [--timers|-o] [--program|-p] [--verbose|-v] [--continuous|-c] [delay]

       netstat              {--route|-r}              [address_family_options]
       [--extend|-e[--extend|-e]]  [--verbose|-v]  [--numeric|-n]  [--numeric-
       hosts][--numeric-ports][--numeric-ports] [--continuous|-c] [delay]

       netstat {--interfaces|-i} [iface] [--all|-a] [--extend|-e[--extend|-e]]
       [--verbose|-v]      [--program|-p]      [--numeric|-n]      [--numeric-
       hosts][--numeric-ports][--numeric-ports] [--continuous|-c] [delay]

       netstat   {--groups|-g}   [--numeric|-n]   [--numeric-hosts][--numeric-
       ports][--numeric-ports] [--continuous|-c] [delay]

       netstat  {--masquerade|-M}  [--extend|-e]  [--numeric|-n]   [--numeric-
       hosts][--numeric-ports][--numeric-ports] [--continuous|-c] [delay]

       netstat {--statistics|-s} [--tcp|-t] [--udp|-u] [--raw|-w] [delay]

       netstat {--version|-V}

       netstat {--help|-h}

       address_family_options:

       [--protocol={inet,unix,ipx,ax25,netrom,ddp}[,...]]          [--unix|-x]
       [--inet|--ip] [--ax25] [--ipx] [--netrom] [--ddp]



DESCRIPTION

       Netstat prints information about the Linux networking  subsystem.   The
       type  of  information  printed  is controlled by the first argument, as
       follows:

   (none)
       By default, netstat displays a list of  open  sockets.   If  you  don’t
       specify any address families, then the active sockets of all configured
       address families will be printed.

   --route , -r
       Display the kernel routing tables.

   --groups , -g
       Display multicast group membership information for IPv4 and IPv6.

   --interface=iface , -i
       Display a table of all network interfaces, or the specified iface).

   --masquerade , -M
       Display a list of masqueraded connections.

   --statistics , -s
       Display summary statistics for each protocol.


OPTIONS

   --verbose , -v
       Tell the user what is going on by being verbose. Especially print  some
       useful information about unconfigured address families.

   --numeric , -n
       Show  numerical addresses instead of trying to determine symbolic host,
       port or user names.

   --numeric-hosts
       shows numerical host addresses but does not affect  the  resolution  of
       port or user names.

   --numeric-ports
       shows numerical port numbers but does not affect the resolution of host
       or user names.

   --numeric-users
       shows numerical user IDs but does not affect the resolution of host  or
       port names.


   --protocol=family , -A
       Specifies  the  address families (perhaps better described as low level
       protocols) for which connections are to be shown.  family  is  a  comma
       (’,’)  separated  list of address family keywords like inet, unix, ipx,
       ax25, netrom, and ddp.  This has the same effect as using  the  --inet,
       --unix (-x), --ipx, --ax25, --netrom, and --ddp options.

       The address family inet includes raw, udp and tcp protocol sockets.

   -c, --continuous
       This  will cause netstat to print the selected information every second
       continuously.

   -e, --extend
       Display additional information.  Use  this  option  twice  for  maximum
       detail.

   -o, --timers
       Include information related to networking timers.

   -p, --program
       Show the PID and name of the program to which each socket belongs.

   -l, --listening
       Show only listening sockets.  (These are omitted by default.)

   -a, --all
       Show  both  listening and non-listening sockets.  With the --interfaces
       option, show interfaces that are not marked

   -F
       Print routing information from the FIB.  (This is the default.)

   -C
       Print routing information from the route cache.

   delay
       Netstat will cycle printing through  statistics  every  delay  seconds.
       UP.



OUTPUT

   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 acknowledged by the remote host.

   Local Address
       Address and port number of the local end of  the  socket.   Unless  the
       --numeric  (-n)  option is specified, the socket address is resolved to
       its canonical host name (FQDN), and the port number is translated  into
       the corresponding service name.

   Foreign Address
       Address  and port number of the remote end of the socket.  Analogous to
       "Local Address."

   State
       The state of the socket. Since there are no states in raw mode and usu-
       ally  no  states  used  in UDP, this column 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 has shut down, and the socket is closed.  Waiting
              for acknowledgement.

       LISTEN The  socket is listening for incoming connections.  Such sockets
              are not included in the output unless you specify the  --listen-
              ing (-l) or --all (-a) option.

       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 username or the user id (UID) of the owner of the socket.

   PID/Program name
       Slash-separated pair of the process id (PID) and process  name  of  the
       process  that  owns  the  socket.   --program  causes this column to be
       included.  You will also need superuser privileges to see this informa-
       tion  on sockets you don’t own.  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.  Such  sockets
              are  only  included in the output if you specify the --listening
              (-l) or --all (-a) option.

       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
       Process ID (PID) and process name of the process that  has  the  socket
       open.  More info available in Active Internet connections section writ-
       ten above.

   Path
       This is 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)



NOTES

       Starting  with  Linux  release  2.2  netstat -i does not show interface
       statistics for alias interfaces. To get per  alias  interface  counters
       you need to setup explicit rules using the ipchains(8) command.



FILES

       /etc/services -- The services translation file

       /proc  --  Mount  point  for the proc filesystem, which gives access to
       kernel status information via the following files.

       /proc/net/dev -- device 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 -- IP routing information

       /proc/net/ax25_route -- AX25 routing information

       /proc/net/ipx_route -- IPX routing information

       /proc/net/nr_nodes -- NET/ROM nodelist

       /proc/net/nr_neigh -- NET/ROM neighbours

       /proc/net/ip_masquerade -- masqueraded connections

       /proc/net/snmp -- statistics



SEE ALSO

       route(8), ifconfig(8), ipchains(8), iptables(8), proc(5)



BUGS

       Occasionally strange information may appear if a socket changes  as  it
       is viewed. This is unlikely to occur.



AUTHORS

       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 by Bernd Eckenfels <ecki@linux.de>.



net-tools                      19 December 2000                     NETSTAT(8)

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