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NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COLOPHON |
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address_families(7) Miscellaneous Information Manual address_families(7)
address_families - socket address families (domains)
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
int socket(int domain, int type, int protocol);
The domain argument of the socket(2) specifies a communication
domain; this selects the protocol family which will be used for
communication. These families are defined in <sys/socket.h>. The
formats currently understood by the Linux kernel include:
AF_UNIX
AF_LOCAL
Local communication. For further information, see unix(7).
AF_INET
IPv4 Internet protocols. For further information, see
ip(7).
AF_AX25
Amateur radio AX.25 protocol. For further information, see
ax25(4).
AF_IPX IPX - Novell protocols.
AF_APPLETALK
AppleTalk For further information, see ddp(7).
AF_NETROM
AX.25 packet layer protocol. For further information, see
netrom(4), The Packet Radio Protocols and Linux
⟨https://www.tldp.org/HOWTO/AX25-HOWTO/x61.html⟩ and the
AX.25, NET/ROM, and ROSE network programming chapters of
the Linux Amateur Radio AX.25 HOWTO
⟨https://www.tldp.org/HOWTO/AX25-HOWTO/x2107.html⟩.
AF_BRIDGE
Can't be used for creating sockets; mostly used for bridge
links in rtnetlink(7) protocol commands.
AF_ATMPVC
Access to raw ATM Permanent Virtual Circuits (PVCs). For
further information, see the ATM on Linux HOWTO
⟨https://www.tldp.org/HOWTO/text/ATM-Linux-HOWTO⟩.
AF_X25 ITU-T X.25 / ISO/IEC 8208 protocol. For further
information, see x25(7).
AF_INET6
IPv6 Internet protocols. For further information, see
ipv6(7).
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 firewall upcalls.
AF_KEY Key management protocol, originally developed for usage
with IPsec (since Linux 2.1.38). This has no relation to
keyctl(2) and the in-kernel key storage facility. See RFC
2367 PF_KEY Key Management API, Version 2
⟨https://tools.ietf.org/html/rfc2367⟩ for details.
AF_NETLINK
Kernel user interface device. For further information, see
netlink(7).
AF_PACKET
Low-level packet interface. For further information, see
packet(7).
AF_ECONET
Acorn Econet protocol (removed in Linux 3.5). See the
Econet documentation
⟨http://www.8bs.com/othrdnld/manuals/econet.shtml⟩ for
details.
AF_ATMSVC
Access to ATM Switched Virtual Circuits (SVCs) See the ATM
on Linux HOWTO
⟨https://www.tldp.org/HOWTO/text/ATM-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), rds-rdma(7),
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).
AF_PPPOX
Generic PPP transport layer, for setting up L2 tunnels
(L2TP and PPPoE). See Documentation/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 Control (The
Institute of Electronics and Electronics Engineers, Inc.,
New York, New York, 1985) for details. See also some
historical notes
⟨https://wiki.linuxfoundation.org/networking/llc⟩ 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), 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 Documentation/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
⟨http://tipc.io/programming.html⟩ and the protocol
description ⟨http://tipc.io/protocol.html⟩ for details.
AF_BLUETOOTH
Bluetooth low-level socket protocol (since Linux 3.11).
See Bluetooth Management API overview
⟨https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc/mgmt-
api.txt⟩ and An Introduction to Bluetooth Programming by
Albert Huang
⟨https://people.csail.mit.edu/albert/bluez-intro/⟩ 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
⟨https://www.ibm.com/support/knowledgecenter/en/SSB27U_6.4.0/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
Documentation/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
⟨http://www.misdn.eu/wiki/Main_Page/⟩ for details.
AF_PHONET
Nokia cellular modem IPC/RPC interface (since Linux
2.6.31). See Documentation/networking/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
Documentation/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).
AF_KCM KCM (kernel connection multiplexer) interface (since Linux
4.6). See Documentation/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 ⟨https://tools.ietf.org/html/rfc7609⟩ for details
regarding SMC-R. See SMC-D Reference Information
⟨https://www-01.ibm.com/software/network/commserver/SMC-
D/index.html⟩ for details regarding SMC-D.
AF_XDP XDP (express data path) interface (since Linux 4.18). See
Documentation/networking/af_xdp.rst in the Linux kernel
source tree for details.
AF_MCTP
MCTP (Management Component Transport Protocol) interface
(since Linux 5.15), as defined by the DMTF specification
DSP0236. For further information, see mctp(7).
socket(2), socket(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
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⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
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[email protected]
Linux man-pages 6.15 2025-05-17 address_families(7)
Pages that refer to this page: socket(2), systemd.exec(5), socket(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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