# phpman > man > address_families(7) [ADDRESS_FAMILIES(7)](https://www.chedong.com/phpMan.php/man/ADDRESSFAMILIES/7/markdown) Linux Programmer's Manual [ADDRESS_FAMILIES(7)](https://www.chedong.com/phpMan.php/man/ADDRESSFAMILIES/7/markdown) ## NAME address_families - socket address families (domains) ## SYNOPSIS **#include** **** /* See NOTES */ ### #include **int** **socket(int** _domain_**,** **int** _type_**,** **int** _protocol_**);** ## DESCRIPTION The _domain_ argument of the [**socket**(2)](https://www.chedong.com/phpMan.php/man/socket/2/markdown) specifies a communication domain; this selects the pro‐ tocol family which will be used for communication. These families are defined in __. The formats currently understood by the Linux kernel include: **AF**___**UNIX**, **AF**___**LOCAL** Local communication For further information, see [**unix**(7)](https://www.chedong.com/phpMan.php/man/unix/7/markdown). **AF**___**INET** IPv4 Internet protocols. For further information, see [**ip**(7)](https://www.chedong.com/phpMan.php/man/ip/7/markdown). **AF**___**AX25** Amateur radio AX.25 protocol. For further information, see [**ax25**(4)](https://www.chedong.com/phpMan.php/man/ax25/4/markdown). **AF**___**IPX** IPX - Novell protocols. **AF**___**APPLETALK** AppleTalk For further information, see [**ddp**(7)](https://www.chedong.com/phpMan.php/man/ddp/7/markdown). **AF**___**NETROM** AX.25 packet layer protocol. For further information, see [**netrom**(4)](https://www.chedong.com/phpMan.php/man/netrom/4/markdown), _The_ _Packet_ _Radio_ _Protocols_ _and_ _Linux_ ⟨⟩ and the _AX.25_, _NET/ROM_, and _ROSE_ _network_ _programming_ chapters of the _Linux_ _Amateur_ _Radio_ _AX.25_ _HOWTO_ ⟨⟩. **AF**___**BRIDGE** Can't be used for creating sockets; mostly used for bridge links in [**rtnetlink**(7)](https://www.chedong.com/phpMan.php/man/rtnetlink/7/markdown) pro‐ tocol commands. **AF**___**ATMPVC** Access to raw ATM Permanent Virtual Circuits (PVCs). For further information, see the _ATM_ _on_ _Linux_ _HOWTO_ ⟨⟩. **AF**___**X25** ITU-T X.25 / ISO-8208 protocol. For further information, see [**x25**(7)](https://www.chedong.com/phpMan.php/man/x25/7/markdown). **AF**___**INET6** IPv6 Internet protocols. For further information, see [**ipv6**(7)](https://www.chedong.com/phpMan.php/man/ipv6/7/markdown). **AF**___**ROSE** RATS (Radio Amateur Telecommunications Society) Open Systems environment (ROSE) AX.25 packet layer protocol. For further information, see the resources listed for **AF**___**NETROM**. **AF**___**DECnet** DECet protocol sockets. See _Documentation/networking/decnet.txt_ in the Linux kernel source tree for details. **AF**___**NETBEUI** Reserved for "802.2LLC project"; never used. **AF**___**SECURITY** This was a short-lived (between Linux 2.1.30 and 2.1.99pre2) protocol family for fire‐ wall upcalls. **AF**___**KEY** Key management protocol, originally developed for usage with IPsec (since Linux 2.1.38). This has no relation to [**keyctl**(2)](https://www.chedong.com/phpMan.php/man/keyctl/2/markdown) and the in-kernel key storage facility. See RFC 2367 _PF_KEY_ _Key_ _Management_ _API,_ _Version_ _2_ ⟨⟩ for details. **AF**___**NETLINK** Kernel user interface device For further information, see [**netlink**(7)](https://www.chedong.com/phpMan.php/man/netlink/7/markdown). **AF**___**PACKET** Low-level packet interface. For further information, see [**packet**(7)](https://www.chedong.com/phpMan.php/man/packet/7/markdown). **AF**___**ECONET** Acorn Econet protocol (removed in Linux 3.5). See the Econet documentation ⟨⟩ for details. **AF**___**ATMSVC** Access to ATM Switched Virtual Circuits (SVCs) See the _ATM_ _on_ _Linux_ _HOWTO_ ⟨⟩ for details. **AF**___**RDS** Reliable Datagram Sockets (RDS) protocol (since Linux 2.6.30). RDS over RDMA has no relation to **AF**___**SMC** or **AF**___**XDP**. For further information see [**rds**(7)](https://www.chedong.com/phpMan.php/man/rds/7/markdown), [**rds-rdma**(7)](https://www.chedong.com/phpMan.php/man/rds-rdma/7/markdown), and _Documentation/networking/rds.txt_ in the Linux kernel source tree. **AF**___**IRDA** Socket interface over IrDA (moved to staging in Linux 4.14, removed in Linux 4.17). For further information see [**irda**(7)](https://www.chedong.com/phpMan.php/man/irda/7/markdown). **AF**___**PPPOX** Generic PPP transport layer, for setting up L2 tunnels (L2TP and PPPoE). See _Documen__‐ _tation/networking/l2tp.txt_ in the Linux kernel source tree for details. **AF**___**WANPIPE** Legacy protocol for wide area network (WAN) connectivity that was used by Sangoma WAN cards (called "WANPIPE"); removed in Linux 2.6.21. **AF**___**LLC** Logical link control (IEEE 802.2 LLC) protocol, upper part of data link layer of ISO/OSI networking protocol stack (since Linux 2.4); has no relation to **AF**___**PACKET**. See chapter _13.5.3._ _Logical_ _Link_ _Control_ in _Understanding_ _Linux_ _Kernel_ _Internals_ (O'Reilly Media, 2006) and _IEEE_ _Standards_ _for_ _Local_ _Area_ _Networks:_ _Logical_ _Link_ _Con__‐ _trol_ (The Institute of Electronics and Electronics Engineers, Inc., New York, New York, 1985) for details. See also some historical notes ⟨⟩ regarding its development. **AF**___**IB** InfiniBand native addressing (since Linux 3.11). **AF**___**MPLS** Multiprotocol Label Switching (since Linux 4.1); mostly used for configuring MPLS routing via [**netlink**(7)](https://www.chedong.com/phpMan.php/man/netlink/7/markdown), as it doesn't expose ability to create sockets to user space. **AF**___**CAN** Controller Area Network automotive bus protocol (since Linux 2.6.25). See _Documenta__‐ _tion/networking/can.rst_ in the Linux kernel source tree for details. **AF**___**TIPC** TIPC, "cluster domain sockets" protocol (since Linux 2.6.16). See _TIPC_ _Programmer's_ _Guide_ ⟨⟩ and the protocol description ⟨⟩ for details. **AF**___**BLUETOOTH** Bluetooth low-level socket protocol (since Linux 3.11). See _Bluetooth_ _Management_ _API_ _overview_ ⟨⟩ and _An_ _Introduction_ _to_ _Bluetooth_ _Programming_ by Albert Huang ⟨⟩ for details. **AF**___**IUCV** IUCV (inter-user communication vehicle) z/VM protocol for hypervisor-guest interaction (since Linux 2.6.21); has no relation to **AF**___**VSOCK** and/or **AF**___**SMC** See _IUCV_ _protocol_ _overview_ ⟨ /com.ibm.zvm.v640.hcpb4/iucv.htm⟩ for details. **AF**___**RXRPC** Rx, Andrew File System remote procedure call protocol (since Linux 2.6.22). See _Docu__‐ _mentation/networking/rxrpc.txt_ in the Linux kernel source tree for details. **AF**___**ISDN** New "modular ISDN" driver interface protocol (since Linux 2.6.27). See the mISDN wiki ⟨⟩ for details. **AF**___**PHONET** Nokia cellular modem IPC/RPC interface (since Linux 2.6.31). See _Documentation/net__‐ _working/phonet.txt_ in the Linux kernel source tree for details. **AF**___**IEEE802154** IEEE 802.15.4 WPAN (wireless personal area network) raw packet protocol (since Linux 2.6.31). See _Documentation/networking/ieee802154.txt_ in the Linux kernel source tree for details. **AF**___**CAIF** Ericsson's Communication CPU to Application CPU interface (CAIF) protocol (since Linux 2.6.36). See _Documentation/networking/caif/Linux-CAIF.txt_ in the Linux kernel source tree for details. **AF**___**ALG** Interface to kernel crypto API (since Linux 2.6.38). See _Documenta__‐ _tion/crypto/userspace-if.rst_ in the Linux kernel source tree for details. **AF**___**VSOCK** VMWare VSockets protocol for hypervisor-guest interaction (since Linux 3.9); has no relation to **AF**___**IUCV** and **AF**___**SMC**. For further information, see [**vsock**(7)](https://www.chedong.com/phpMan.php/man/vsock/7/markdown). **AF**___**KCM** KCM (kernel connection multiplexer) interface (since Linux 4.6). See _Documenta__‐ _tion/networking/kcm.txt_ in the Linux kernel source tree for details. **AF**___**QIPCRTR** Qualcomm IPC router interface protocol (since Linux 4.7). **AF**___**SMC** SMC-R (shared memory communications over RDMA) protocol (since Linux 4.11), and SMC-D (shared memory communications, direct memory access) protocol for intra-node z/VM quest interaction (since Linux 4.19); has no relation to **AF**___**RDS**, **AF**___**IUCV** or **AF**___**VSOCK**. See RFC 7609 _IBM's_ _Shared_ _Memory_ _Communications_ _over_ _RDMA_ _(SMC-R)_ _Protocol_ ⟨⟩ for details regarding SMC-R. See _SMC-D_ _Reference_ _Information_ ⟨- D/index.html⟩ for details regarding SMC-D. **AF**___**XDP** XDP (express data path) interface (since Linux 4.18). See _Documentation/network__‐ _ing/af_xdp.rst_ in the Linux kernel source tree for details. ## SEE ALSO [**socket**(2)](https://www.chedong.com/phpMan.php/man/socket/2/markdown), [**socket**(7)](https://www.chedong.com/phpMan.php/man/socket/7/markdown) ## COLOPHON This page is part of release 5.10 of the Linux _man-pages_ project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at . Linux 2018-10-16 [ADDRESS_FAMILIES(7)](https://www.chedong.com/phpMan.php/man/ADDRESSFAMILIES/7/markdown)