从字面理解：
AF_INET = Address Format, Internet = IP Addresses
PF_INET = Packet Format, Internet = IP, TCP/IP or UDP
从linux的定义来看，两者无区别。
/* Supported address families. */
#define AF_UNSPEC 0#define AF_UNIX 1 /* Unix domain sockets */#define AF_LOCAL 1 /* POSIX name for AF_UNIX */#define AF_INET 2 /* Internet IP Protocol */#define AF_AX25 3 /* Amateur Radio AX.25 */#define AF_IPX 4 /* Novell IPX */#define AF_APPLETALK 5 /* AppleTalk DDP */#define AF_NETROM 6 /* Amateur Radio NET/ROM */#define AF_BRIDGE 7 /* Multiprotocol bridge */#define AF_ATMPVC 8 /* ATM PVCs */#define AF_X25 9 /* Reserved for X.25 project */#define AF_INET6 10 /* IP version 6 */#define AF_ROSE 11 /* Amateur Radio X.25 PLP */#define AF_DECnet 12 /* Reserved for DECnet project */#define AF_NETBEUI 13 /* Reserved for 802.2LLC project*/#define AF_SECURITY 14 /* Security callback pseudo AF */#define AF_KEY 15 /* PF_KEY key management API */#define AF_NETLINK 16#define AF_ROUTE AF_NETLINK /* Alias to emulate 4.4BSD */#define AF_PACKET 17 /* Packet family */#define AF_ASH 18 /* Ash */#define AF_ECONET 19 /* Acorn Econet */#define AF_ATMSVC 20 /* ATM SVCs */#define AF_RDS 21 /* RDS sockets */#define AF_SNA 22 /* Linux SNA Project (nutters!) */#define AF_IRDA 23 /* IRDA sockets */#define AF_PPPOX 24 /* PPPoX sockets */#define AF_WANPIPE 25 /* Wanpipe API Sockets */#define AF_LLC 26 /* Linux LLC */#define AF_CAN 29 /* Controller Area Network */#define AF_TIPC 30 /* TIPC sockets */#define AF_BLUETOOTH 31 /* Bluetooth sockets */#define AF_IUCV 32 /* IUCV sockets */#define AF_RXRPC 33 /* RxRPC sockets */#define AF_ISDN 34 /* mISDN sockets */#define AF_PHONET 35 /* Phonet sockets */#define AF_IEEE802154 36 /* IEEE802154 sockets */#define AF_CAIF 37 /* CAIF sockets */#define AF_ALG 38 /* Algorithm sockets */#define AF_MAX 39 /* For now.. *//* Protocol families, same as address families. */
#define PF_UNSPEC AF_UNSPEC#define PF_UNIX AF_UNIX#define PF_LOCAL AF_LOCAL#define PF_INET AF_INET#define PF_AX25 AF_AX25#define PF_IPX AF_IPX#define PF_APPLETALK AF_APPLETALK#define PF_NETROM AF_NETROM#define PF_BRIDGE AF_BRIDGE#define PF_ATMPVC AF_ATMPVC#define PF_X25 AF_X25#define PF_INET6 AF_INET6#define PF_ROSE AF_ROSE#define PF_DECnet AF_DECnet#define PF_NETBEUI AF_NETBEUI#define PF_SECURITY AF_SECURITY#define PF_KEY AF_KEY#define PF_NETLINK AF_NETLINK#define PF_ROUTE AF_ROUTE#define PF_PACKET AF_PACKET#define PF_ASH AF_ASH#define PF_ECONET AF_ECONET#define PF_ATMSVC AF_ATMSVC#define PF_RDS AF_RDS#define PF_SNA AF_SNA#define PF_IRDA AF_IRDA#define PF_PPPOX AF_PPPOX#define PF_WANPIPE AF_WANPIPE#define PF_LLC AF_LLC#define PF_CAN AF_CAN#define PF_TIPC AF_TIPC#define PF_BLUETOOTH AF_BLUETOOTH#define PF_IUCV AF_IUCV#define PF_RXRPC AF_RXRPC#define PF_ISDN AF_ISDN#define PF_PHONET AF_PHONET#define PF_IEEE802154 AF_IEEE802154#define PF_CAIF AF_CAIF#define PF_ALG AF_ALG#define PF_MAX AF_MAX
从