Unix domain socket

A Unix domain socket or IPC socket (inter-process communication socket) is a data communications endpoint that is similar to an Internet socket, but does not use a network protocol for communication. It is used in POSIX operating systems for inter-process communication. The correct standard POSIX term is POSIX Local IPC Sockets.

Unix domain connections appear as byte streams, much like network connections, but all data remains within the local computer. UNIX domain sockets use the file system as address name space, i.e. they are referenced by processes as inodes in the file system. This allows two distinct processes to open the same socket in order to communicate. However, the actual communication (the data exchange) does not use the file system, but buffers in kernel memory.

In addition to sending data, processes can send file descriptors across a Unix domain socket connection (including file descriptors for domain sockets) using the sendmsg() and recvmsg() system calls. This means that domain sockets can be used as an object-capability communication system.

See also

• Berkeley sockets

External links

• socketpair(2): create a pair of connected sockets – Linux man page
• sendmsg(2): send a message on a socket – Linux man page
• recvmsg(2): receive a message from a socket – Linux man page
• cmsg(3): socket ancillary data, including sending/receiving file descriptors – Linux man page
• ucspi-unix, UNIX-domain socket client-server command-line tools
• unix domain sockets
• Unix sockets vs Internet sockets
• Unix Domain Sockets for Java

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