UNIX domain socket

http://en.wikipedia.org/wiki/Unix_domain_socket

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A Unix domain socket (UDS) or IPC socket (inter-process communication socket) is a virtual socket, similar to an internet socket that is used in POSIX operating systems for inter-process communication. The correct standard POSIX term is POSIX Local IPC Sockets.

These 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 the address name space, i.e they use files to communicate.

In addition to sending data, processes can send file descriptors across a Unix domain socket connection using the sendmsg() and recvmsg() system calls.

내부적으로 통신을 하기위해 가상으로 만들어놓은 소켓의 일종으로 IPC에 사용됩니다.