Linux Cli Netstat

Mon, 03 Jun 2024 12:29:55 +0800
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NETSTAT(8)									     Linux System Administrator's Manual									  NETSTAT(8)

NAME
       netstat - Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships

SYNOPSIS
       netstat	[address_family_options]  [--tcp|-t]  [--udp|-u]  [--udplite|-U]  [--sctp|-S]  [--raw|-w]  [--l2cap|-2]	 [--rfcomm|-f]	[--listening|-l]  [--all|-a] [--numeric|-n] [--numeric-hosts] [--nu‐
       meric-ports] [--numeric-users] [--symbolic|-N] [--extend|-e[--extend|-e]] [--timers|-o] [--program|-p] [--verbose|-v] [--continuous|-c] [--wide|-W]

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

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

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

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

       netstat {--statistics|-s} [--tcp|-t] [--udp|-u] [--udplite|-U] [--sctp|-S] [--raw|-w]

       netstat {--version|-V}

       netstat {--help|-h}

       address_family_options:

       [-4|--inet] [-6|--inet6] [--protocol={inet,inet6,unix,ipx,ax25,netrom,ddp,bluetooth, ... } ] [--unix|-x] [--inet|--ip|--tcpip] [--ax25] [--x25] [--rose]	 [--ash]  [--bluetooth]	 [--ipx]  [--netrom]
       [--ddp|--appletalk] [--econet|--ec]

NOTES
       This program is mostly obsolete.	 Replacement for netstat is ss.	 Replacement for netstat -r is ip route.  Replacement for netstat -i is ip -s link.  Replacement for netstat -g is ip maddr.

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. See the description in route(8) for details.	netstat -r and route -e produce the same output.

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

   --interfaces, -i
       Display a table of all network interfaces.

   --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.

   --wide, -W
       Do not truncate IP addresses by using output as wide as needed. This is optional for now to not break existing scripts.

   --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,
       inet6, unix, ipx, ax25, netrom, econet, ddp, and bluetooth.  This has the same effect as using the --inet|-4, --inet6|-6, --unix|-x, --ipx, --ax25, --netrom, --ddp, and --bluetooth options.

       The address family inet (Iv4) includes raw, udp, udplite and tcp protocol sockets.

       The address family bluetooth (Iv4) includes l2cap and rfcomm 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 up

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

   -C
       Print routing information from the route cache.

OUTPUT
   Active Internet connections (TCP, UDP, UDPLite, raw)
   Proto
       The protocol (tcp, udp, udpl, raw) used by the socket.

   Recv-Q
       Established: The count of bytes not copied by the user program connected to this socket.	 Listening: Since Kernel 2.6.18 this column contains the current syn backlog.

   Send-Q
       Established: The count of bytes not acknowledged by the remote host.  Listening: Since Kernel 2.6.18 this column contains the maximum size of the syn backlog.

   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 usually no states used in UDP and UDPLite, 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.

       CLOSE  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 --listening (-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
       information 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 re‐
       quest. 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 written 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)

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/udplite -- UDPLite 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

       /sys/kernel/debug/bluetooth/l2cap -- Bluetooth L2CAP information

       /sys/kernel/debug/bluetooth/rfcomm -- Bluetooth serial connections

       /proc/net/snmp -- statistics

SEE ALSO
       route(8), ifconfig(8), iptables(8), proc(5) ss(8) ip(8)

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>, 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>.	 UD‐
       PLite options were added by Brian Micek <bmicek@gmail.com>

net-tools											 2014-10-07											  NETSTAT(8)
Netstat on PolloChang 工作筆記

Linux Cli Netstat

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