A Unix Domain socket (UDS) or IPC socket (inter-process communication) is a data communication endpoint for exchanging data between processes executing on the same host operating system. It is also referred by its address family AF_UNIX

Differently from TCP/IP sockets, a UDS operates on a single machine. Listening sockets live in the filesystem hierarchy and access to them can be controlled by filesystem permission.

A process accepting connections on a Unix socket can determine the user ID of the process that connects.

The API for UDS is similar to that of an network-sockets, but rather than using an underlying network protocol, all communication occurs entirely within the operating system kernel.

In addition to sending data, processes may send file-descriptors across a Unix domain socket connection using the sendmsg() and recvmsg() system calls. This allows the sending processes to grant the receiving process access to a file descriptor for which the receiving process otherwise doesn’t have access.

References

• https://en.wikipedia.org/wiki/Unix_domain_socket
• https://serverfault.com/questions/124517/what-is-the-difference-between-unix-sockets-and-tcp-ip-sockets

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