LinkCreate["name"] creates a MathLink link with the specified name for another program to connect to.
LinkCreate[ ] picks an unused port on your computer system and creates a MathLink link on it.
LinkCreate returns a LinkObject.
You can use LinkCreate and LinkConnect to set up peer-to-peer communication between two Mathematica processes.
The option LinkProtocol specifies the underlying data transport protocol to use.
LinkCreate internally calls a function analogous to the MLOpenArgv() function in the MathLink library.
See The Mathematica Book: Section 2.12.6.
See also: LinkConnect, LinkLaunch, LinkClose.