socket - summary of local and internet protocol

	Domain	Socket Type	Description/Notes
1	PF_LOCAL	SOCK_STREAM	Provides a stream-oriented socket within the local host. This is a connection-oriented service— reliable and sequenced. Note that PF_UNIX is equivalent to PF_LOCAL
2	PF_LOCAL	SOCK_DGRAM	Provides datagram services within the local host. Note that this service is connectionless, but reliable, with the possible exception that packets might be lost if kernel buffers should become exhausted.
3	PF_INET	SOCK_STREAM	Stream I/O services for Internet connected sockets. Implies the TCP/IP protocol— reliable and sequenced.
4	PF_INET	SOCK_DGRAM	Datagram I/O services for Internet connectionless sockets. This combination implies UDP (User Datagram Protocol). This service is unreliable.
5	PF_INET6	SOCK_STREAM	Stream I/O services for Internet IPv6 connected sockets. Implies the TCP/IP protocol, reliable, and sequenced.
6	PF_INET6	SOCK_SEQPACKET	Stream I/O services for Internet IPv6 connected sockets. Implies the use of the TCP/IP protocol. This service is reliable, message boundaries are preserved, and sequence of data is preserved.
7	PF_INET6	SOCK_DGRAM	Datagram I/O services for Internet IPv6 connectionless sockets. This combination implies UDP (User Datagram Protocol). This service is unreliable.