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🏷️ NAME

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

🚀 Quick Reference

Use Case	Command	Description
🔍 Show all listening TCP/UDP sockets with PID	netstat -tulpn	Display listening ports and associated programs
🌐 Show all connections (numeric, no DNS)	netstat -an	List all sockets with numeric addresses/ports
🗺️ Display routing table	netstat -r	Show kernel IP routing table
📡 Show network interfaces	netstat -i	List interface statistics (packets, errors)
📊 Protocol statistics	netstat -s	Summary of TCP, UDP, ICMP, etc. counters
🔄 Continuous refresh	netstat -c	Print selected info every second
👥 Multicast group memberships	netstat -g	Show IPv4/IPv6 multicast groups
🎭 Masqueraded connections	netstat -M	List NAT/masquerade entries
⏱️ Show timers	netstat -o	Include networking timer info

📋 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]  [--numeric-ports]  [--nu-
       meric-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[--ex-
       tend|-e]]   [--verbose|-v]   [--numeric|-n]   [--numeric-hosts]  [--nu-
       meric-ports] [--numeric-users] [--continuous|-c]

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

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

       netstat    {--masquerade|-M}    [--extend|-e]   [--numeric|-n]   [--nu-
       meric-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]                   [--proto-
       col={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 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 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 AT insu1.de>, the man page basically by Matt Welsh <mdw AT tc.edu>. It was updated by Alan Cox <Alan.Cox AT 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 AT linux.de>. UDPLite options were added by Brian Micek <bmicek AT gmail.com>

net-tools 2014-10-07 NETSTAT(8)

🏷️ NAME 🚀 Quick Reference 📋 SYNOPSIS 📝 NOTES 📖 DESCRIPTION ⚙️ OPTIONS 📊 OUTPUT 📁 FILES 🔗 SEE ALSO 🐛 BUGS 👤 AUTHORS