NETSTAT(1)

💖 NETSTAT(1) — show network status 💖

okay bestie, this is the netstat(1) page from the General Commands Manual, and she is that girl when it comes to peeking at network status. ✨

🎀 NAME 🎀

netstat — show network status 💅

✨ SYNOPSIS ✨

netstat [-AaLlnW] [-f address_family | -p protocol]
netstat [-gilns] [-v] [-f address_family] [-I interface]
netstat -i | -I interface [-w wait] [-c queue] [-abdgqRtS]
netstat -s [-s] [-f address_family | -p protocol] [-w wait]
netstat -i | -I interface -s [-f address_family | -p protocol]
netstat -m [-m]
netstat -r [-Aaln] [-f address_family]
netstat -rs [-s]
netstat -B [-I interface]

🦋 DESCRIPTION 🦋

okay so the netstat command symbolically displays the contents of various network-related data structures. There are a number of output formats, depending on the options for the information presented. 🫶

1. First form: displays a list of active sockets for each protocol. 👑
2. Second form: presents the contents of one of the other network data structures according to the option selected. 🎀
3. Third form: with a wait interval specified, netstat will continuously display the information regarding packet traffic on the configured network interfaces. 🔥
4. Fourth form: displays statistics for the specified protocol or address family. If a wait interval is specified, the protocol information over the last interval seconds will be displayed. ⭐
5. Fifth form: displays per-interface statistics for the specified protocol or address family. 🌸
6. Sixth form: displays mbuf(9) statistics. 🧚
7. Seventh form: displays routing table for the specified address family. 🌈
8. Eighth form: displays routing statistics. 💜

💅 OPTIONS: the tea on each flag 💅

The options have the following meaning:

• -A — With the default display, show the address of any protocol control blocks associated with sockets and the flow hash; used for debugging. 🔍
• -a — With the default display, show the state of all sockets; normally sockets used by server processes are not shown. With the routing table display (option -r, as described below), show protocol-cloned routes (routes generated by a RTF_PRCLONING parent route); normally these routes are not shown. 👀
• -B — Show statistics about bpf(4) devices. This includes information like how many packets have been matched, dropped and received by the bpf device, also information about current buffer sizes and device states. The option -I show information only for the bpf devices bound the specified interface. 🫧
• -b — With the interface display (option -i, as described below), show the number of bytes in and out. 📥📤
• -c queue — With the queue statistics (option -q, as described below), show only those for the specified queue. 🎯
• -d — With either interface display (option -i or an interval, as described below), show the number of dropped packets. 💀
• -f address_family — Limit statistics or address control block reports to those of the specified address family. The following address families are recognized: inet, for AF_INET, inet6, for AF_INET6, unix, for AF_UNIX and vsock, for AF_VSOCK. 🌐
• -g — Show information related to multicast (group address) membership. If the -s option is also present, show extended interface group management statistics. If the -v option is specified, show link-layer memberships; they are suppressed by default. Source lists for each group will also be printed. Specifying -v twice will print the control plane timers for each interface and the source list counters for each group. If the -i is specified, only that interface will be shown. If the -f is specified, only information for the address family will be displayed. 🫶
• -I interface — Show information about the specified interface; used with a wait interval as described below. If the -s option is present, show per-interface protocol statistics on the interface for the specified address_family or protocol, or for all protocol families. 🎀
• -i — Show the state of interfaces which have been auto-configured (interfaces statically configured into a system, but not located at boot time are not shown). If the -a options is also present, multicast addresses currently in use are shown for each Ethernet interface and for each IP interface address. Multicast addresses are shown on separate lines following the interface address with which they are associated. If the -s option is present, show per-interface statistics on all interfaces for the specified address_family or protocol, or for all protocol families. 🦋
• -L — Show the size of the various listen queues. The first count shows the number of unaccepted connections. The second count shows the amount of unaccepted incomplete connections. The third count is the maximum number of queued connections. 📚
• -l — Print full IPv6 address. 🌈
• -m — Show statistics recorded by the memory management routines (the network stack manages a private pool of memory buffers). More detailed information about the buffers, which includes their cache related statistics, can be obtained by using -mm or -m -m option. 🧠
• -n — Show network addresses as numbers (normally netstat interprets addresses and attempts to display them symbolically). This option may be used with any of the display formats. 🔢
• -p protocol — Show statistics about protocol, which is either a well-known name for a protocol or an alias for it. Some protocol names and aliases are listed in the file /etc/protocols. The special protocol name “bdg” is used to show bridging statistics. A null response typically means that there are no interesting numbers to report. The program will complain if protocol is unknown or if there is no statistics routine for it. 🌉
• -q — Show network interface send queue statistics. By default all queues are displayed, unless specified with -c. This option requires specifying an interface with -I option. More detailed information about the queues, which includes their queueing algorithm related statistics, can be obtained by using -qq or -q -q option. 🚀
• -r — Show the routing tables. Use with -a to show protocol-cloned routes. When -s is also present, show routing statistics instead. When -l is also present, netstat assumes more columns are there and the maximum transmission unit. More detailed information about the route metrics are displayed with -ll for TCP round trip times -lll for all metrics. Use the -z flags to display only entries with non-zero RTT values. (“mtu”) are also displayed. 🗺️
• -R — Show reachability information. Use with -i to show link-layer reachability information for a given interface. 📡
• -s — Show per-protocol statistics. If this option is repeated, counters with a value of zero are suppressed. For security reasons, root privileges are required to read TCP statistics and in the absence of such privileges all TCP counters will be reported as zero. 🔐
• -S — Show interface link status and interface state information about the specified interface. This option requires specifying an interface with -I option. 🚦
• -v — Increase verbosity level. 🗣️
• -W — In certain displays, avoid truncating addresses even if this causes some fields to overflow. 🧩
• -w wait — Show network interface or protocol statistics at intervals of wait seconds. ⏳
• -x — Show extended link-layer reachability information in addition to that shown by the -R flag. 🛰️

💖 OUTPUT 💖

Okay bestie, here's the tea on what netstat actually shows you. The default display, for active sockets, is giving local and remote addresses, send and receive queue sizes (in bytes), protocol, and the internal state of the protocol. Address formats are of the form host.port or network.port if a socket's address specifies a network but no specific host address. If known, the host and network addresses are displayed symbolically according to the databases /etc/hosts and /etc/networks, respectively. If a symbolic name for an address is unknown, or if the -n option is specified, the address is printed numerically, according to the address family. For more information regarding the Internet “dot format”, peep inet(3). Unspecified, or “wildcard”, addresses and ports appear as *.

🌈 Internet domain socket states 🌈

These are the states you'll see, and yes they're lowkey dramatic:

• CLOSED — The socket is not in use.
• LISTEN — The socket is listening for incoming connections. Unconnected listening sockets like these are only displayed when using the -a option.
• SYN_SENT — The socket is actively trying to establish a connection to a remote peer.
• SYN_RCVD — The socket has passively received a connection request from a remote peer.
• ESTABLISHED — The socket has an established connection between a local application and a remote peer.
• CLOSE_WAIT — The socket connection has been closed by the remote peer, and the system is waiting for the local application to close its half of the connection.
• LAST_ACK — The socket connection has been closed by the remote peer, the local application has closed its half of the connection, and the system is waiting for the remote peer to acknowledge the close.
• FIN_WAIT_1 — The socket connection has been closed by the local application, the remote peer has not yet acknowledged the close, and the system is waiting for it to close its half of the connection.
• FIN_WAIT_2 — The socket connection has been closed by the local application, the remote peer has acknowledged the close, and the system is waiting for it to close its half of the connection.
• CLOSING — The socket connection has been closed by the local application and the remote peer simultaneously, and the remote peer has not yet acknowledged the close attempt of the local application.
• TIME_WAIT — The socket connection has been closed by the local application, the remote peer has closed its half of the connection, and the system is waiting to be sure that the remote peer received the last acknowledgement.

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The interface display provides a table of cumulative statistics regarding packets transferred, errors, and collisions. The network addresses of the interface and the maximum transmission unit (“mtu”) are also displayed.

The routing table display indicates the available routes and their status. Each route consists of a destination host or network and a gateway to use in forwarding packets. The flags field shows a collection of information about the route stored as binary choices. The individual flags are discussed in more detail in the route(8) and route(4) manual pages. The mapping between letters and flags is:

• 1 — RTF_PROTO1: Protocol specific routing flag #1
• 2 — RTF_PROTO2: Protocol specific routing flag #2
• 3 — RTF_PROTO3: Protocol specific routing flag #3
• B — RTF_BLACKHOLE: Just discard packets (during updates)
• b — RTF_BROADCAST: The route represents a broadcast address
• C — RTF_CLONING: Generate new routes on use
• c — RTF_PRCLONING: Protocol-specified generate new routes on use
• D — RTF_DYNAMIC: Created dynamically (by redirect)
• G — RTF_GATEWAY: Destination requires forwarding by intermediary
• H — RTF_HOST: Host entry (net otherwise)
• I — RTF_IFSCOPE: Route is associated with an interface scope
• i — RTF_IFREF: Route is holding a reference to the interface
• L — RTF_LLINFO: Valid protocol to link address translation
• M — RTF_MODIFIED: Modified dynamically (by redirect)
• m — RTF_MULTICAST: The route represents a multicast address
• R — RTF_REJECT: Host or net unreachable
• r — RTF_ROUTER: Host is a default router
• S — RTF_STATIC: Manually added
• U — RTF_UP: Route usable
• W — RTF_WASCLONED: Route was generated as a result of cloning
• X — RTF_XRESOLVE: External daemon translates proto to link address
• Y — RTF_PROXY: Proxying; cloned routes will not be scoped
• g — RTF_GLOBAL: Route to a destination of the global internet (policy hint)

Direct routes are created for each interface attached to the local host; the gateway field for such entries shows the address of the outgoing interface. The refcnt field gives the current number of active uses of the route. Connection oriented protocols normally hold on to a single route for the duration of a connection while connectionless protocols obtain a route while sending to the same destination. The use field provides a count of the number of packets sent using that route. The interface entry indicates the network interface utilized for the route. A route which is marked with the RTF_IFSCOPE flag is instantiated for the corresponding interface. A cloning route which is marked with the RTF_PROXY flag will not generate new routes that are associated with its interface scope.

When netstat is invoked with the -w option and a wait interval argument, it displays a running count of statistics related to network interfaces or protocols. By default, this display summarizes information for all interfaces. Information for a specific interface may be displayed with the -I option.

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🌸 SEE ALSO 🌸

Go stalk these bad boys: nfsstat(1), ps(1), inet(4), unix(4), hosts(5), networks(5), protocols(5), route(8), services(5), iostat(8), bpf(4).

🦋 HISTORY 🦋

The netstat command appeared in 4.2BSD. IPv6 support was added by WIDE/KAME project.

💀 BUGS 💀

Okay so this is the whole bug section and it's giving “we don't really know”: The notion of errors is ill-defined. 😭

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This lil icon is repping source/version Darwin and date June 15, 2001, living its best life as NETSTAT(1) — byeee bestie, go check your sockets 💅✨🫶