AUnix domain socket (UDS),local socket, orinter-process communication (IPC)socket is acommunication endpoint forexchanging data between processes executing in the sameUnix orUnix-like operating system.

The nameUnix domain socket refers to thedomain argument valueAF_UNIX that is passed to the function that creates a socketsystem resource. The same communication domain is also selected byAF_LOCAL.^[1]

Validtype argument values for a UDS are:^[1]

• SOCK_STREAM (compare toTCP) – for a stream-oriented socket
• SOCK_DGRAM (compare toUDP) – for a datagram-oriented socket that preserves message boundaries (as on most UNIX implementations, UNIX domain datagram sockets are always reliable and don't reorder datagrams)
• SOCK_SEQPACKET (compare toSCTP) – for a sequenced-packet socket that is connection-oriented, preserves message boundaries, and delivers messages in the order that they were sent

The UDS facility is a standard component of aPOSIXoperating system.

TheAPI for a UDS is similar to that of anInternet socket, but rather than using an underlying network protocol, all communication occurs entirely within the operating systemkernel. A UDS may use the file system as its addressnamespace. Some operating systems, likeLinux, offer additional namespaces. Processes reference a UDS as a file systeminode, so two processes can communicate by opening the same socket.

In addition to sending data, processes may sendfile descriptors across a UDS connection using thesendmsg() andrecvmsg() system calls. This allows the sending processes to grant the receiving process access to a file descriptor for which the receiving process otherwise does not have access.^[2][3] This can be used to implement a rudimentary form ofcapability-based security.^[4]

• Network socket – Software-based endpoint of network communications
• Berkeley sockets – Inter-process communication API
• Pipeline (Unix) – Mechanism for inter-process communication using message passing
• Netlink – Linux kernel interface for inter-process communication between processes

• socket – System Interfaces Reference,The Single UNIX Specification, Version 5 fromThe Open Group
• socketpair – System Interfaces Reference,The Single UNIX Specification, Version 5 fromThe Open Group
• sendmsg – System Interfaces Reference,The Single UNIX Specification, Version 5 fromThe Open Group
• recvmsg – System Interfaces Reference,The Single UNIX Specification, Version 5 fromThe Open Group
• cmsg(3) – Linux Programmer'sManual – Library Functions from Manned.org
• ucspi-unix, UNIX-domain socket client-server command-line tools
• Unix sockets vs Internet sockets
• Unix Sockets - Beej's Guide to Unix IPC

• Network socket
• Unix

• Articles with short description
• Short description is different from Wikidata
• Use dmy dates from January 2019