Linux "netstat" Command Line Options and Examples
Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships

Netstat prints information about the Linux networking subsystem. The type of information printed is controlled by the first argu‐ ment, 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 con‐ figured address families will be printed.


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

Command Line Options:

Tell the user what is going on by being verbose. Especially print some useful information about unconfigured address families.
netstat --verbose ...
Do not truncate IP addresses by using output as wide as needed. This is optional for now to not break existing scripts.
netstat --wide ...
Show numerical addresses instead of trying to determine symbolic host, port or user names.
netstat --numeric ...
shows numerical host addresses but does not affect the resolution of port or user names.
netstat --numeric-hosts ...
shows numerical port numbers but does not affect the resolution of host or user names.
netstat --numeric-ports ...
shows numerical user IDs but does not affect the resolution of host or port names.
netstat --numeric-users ...
Specifies the address families (perhaps better described as low level protocols) for which connections are to be shown. family is acomma (',') separated list of address family keywords like inet, inet6, unix, ipx, ax25, netrom, econet, ddp, and bluetooth. Thishas 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.
netstat --protocol ...
This will cause netstat to print the selected information every second continuously.
netstat -c ...
Display additional information. Use this option twice for maximum detail.
netstat -e ...
Include information related to networking timers.
netstat -o ...
Show the PID and name of the program to which each socket belongs.
netstat -p ...
Show only listening sockets. (These are omitted by default.)
netstat -l ...
Show both listening and non-listening sockets. With the --interfaces option, show interfaces that are not up
netstat -a ...
Print routing information from the FIB. (This is the default.)
netstat -F ...
Print routing information from the route cache.OUTPUTActive Internet connections (TCP, UDP, UDPLite, raw)ProtoThe protocol (tcp, udp, udpl, raw) used by the socket.Recv-QEstablished: The count of bytes not copied by the user program connected to this socket. Listening: Since Kernel 2.6.18 this columncontains the current syn backlog.Send-QEstablished: The count of bytes not acknowledged by the remote host. Listening: Since Kernel 2.6.18 this column contains the maximumsize of the syn backlog.Local AddressAddress and port number of the local end of the socket. Unless the --numeric (-n) option is specified, the socket address isresolved to its canonical host name (FQDN), and the port number is translated into the corresponding service name.Foreign AddressAddress and port number of the remote end of the socket. Analogous to "Local Address".StateThe 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 leftblank. Normally this can be one of several values:ESTABLISHEDThe socket has an established connection.SYN_SENTThe socket is actively attempting to establish a connection.SYN_RECVA connection request has been received from the network.FIN_WAIT1The socket is closed, and the connection is shutting down.FIN_WAIT2Connection is closed, and the socket is waiting for a shutdown from the remote end.TIME_WAITThe socket is waiting after close to handle packets still in the network.CLOSE The socket is not being used.CLOSE_WAITThe remote end has shut down, waiting for the socket to close.LAST_ACKThe 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 --lis‐tening (-l) or --all (-a) option.CLOSINGBoth sockets are shut down but we still don't have all our data sent.UNKNOWNThe state of the socket is unknown.UserThe username or the user id (UID) of the owner of the socket.PID/Program nameSlash-separated pair of the process id (PID) and process name of the process that owns the socket. --program causes this column tobe included. You will also need superuser privileges to see this information on sockets you don't own. This identification informa‐tion is not yet available for IPX sockets.Timer(this needs to be written)Active UNIX domain SocketsProtoThe protocol (usually unix) used by the socket.RefCntThe reference count (i.e. attached processes via this socket).FlagsThe flags displayed is SO_ACCEPTON (displayed as ACC), SO_WAITDATA (W) or SO_NOSPACE (N). SO_ACCECPTON is used on unconnected sock‐ets if their corresponding processes are waiting for a connect request. The other flags are not of normal interest.TypeThere are several types of socket access:SOCK_DGRAMThe socket is used in Datagram (connectionless) mode.SOCK_STREAMThis is a stream (connection) socket.SOCK_RAWThe socket is used as a raw socket.SOCK_RDMThis one serves reliably-delivered messages.SOCK_SEQPACKETThis is a sequential packet socket.SOCK_PACKETRaw interface access socket.UNKNOWNWho ever knows what the future will bring us - just fill in here :-)StateThis field will contain one of the following Keywords:FREE The socket is not allocatedLISTENINGThe socket is listening for a connection request. Such sockets are only included in the output if you specify the --listening
netstat -C ...
CONNECTINGThe socket is about to establish a connection.CONNECTEDThe socket is connected.DISCONNECTINGThe socket is disconnecting.(empty)The socket is not connected to another one.UNKNOWNThis state should never happen.PID/Program nameProcess ID (PID) and process name of the process that has the socket open. More info available in Active Internet connections sec‐tion written above.PathThis 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
netstat -l) ...