unix:// and udg://.
unix:///tmp/mysockudg:///tmp/mysockunix:// provides access to a socket stream connection in the Unix domain. udg:// provides an alternate transport to a Unix domain socket using the user datagram protocol.
Unix domain sockets, unlike Internet domain sockets, do not expect a port number. In the case of fsockopen() the portno parameter should be set to 0.
Note: Unix domain sockets are not supported on Windows.