socket ======================================== socket函数的原型为 ``int socket(int domain, int type, int protocol);`` 。 其中domain即协议域，又称为协议族(family)。常用的协议族有AF_INET、AF_INET6、AF_LOCAL(或称AF_UNIX，Unix域socket)、AF_ROUTE等等。协议族决定了socket的地址类型，在通信中必须采用对应的地址，如AF_INET决定了要用IPv4地址(32位的)与端口号(16位的)的组合、AF_UNIX要使用一个绝对路径名作为地址。 支持的所有协议定义在 ``/include/linux/socket.h`` 中，具体内容如下： .. code-block:: c /* 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_IB 27 /* Native InfiniBand address */ #define AF_MPLS 28 /* MPLS */ #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_NFC 39 /* NFC sockets */ #define AF_VSOCK 40 /* vSockets */ #define AF_KCM 41 /* Kernel Connection Multiplexor*/ #define AF_QIPCRTR 42 /* Qualcomm IPC Router */ #define AF_SMC 43 /* smc sockets: reserve number for * PF_SMC protocol family that * reuses AF_INET address family */ #define AF_XDP 44 /* XDP sockets */ #define AF_MAX 45 /* For now.. */ type指定socket类型，常用的socket类型为: .. code-block:: c enum sock_type { SOCK_STREAM = 1, // 字节流套接字 SOCK_DGRAM = 2, // 数据报文套接字 SOCK_RAW = 3, // 原始套接字 SOCK_RDM = 4, SOCK_SEQPACKET = 5, // 有序分组套接字 SOCK_DCCP = 6, SOCK_PACKET = 10, }; protocol指协议，常用的协议类型为: .. code-block:: c /* Standard well-defined IP protocols. */ enum { IPPROTO_IP = 0, /* Dummy protocol for TCP */ #define IPPROTO_IP IPPROTO_IP IPPROTO_ICMP = 1, /* Internet Control Message Protocol */ #define IPPROTO_ICMP IPPROTO_ICMP IPPROTO_IGMP = 2, /* Internet Group Management Protocol */ #define IPPROTO_IGMP IPPROTO_IGMP IPPROTO_IPIP = 4, /* IPIP tunnels (older KA9Q tunnels use 94) */ #define IPPROTO_IPIP IPPROTO_IPIP IPPROTO_TCP = 6, /* Transmission Control Protocol */ #define IPPROTO_TCP IPPROTO_TCP IPPROTO_EGP = 8, /* Exterior Gateway Protocol */ #define IPPROTO_EGP IPPROTO_EGP IPPROTO_PUP = 12, /* PUP protocol */ #define IPPROTO_PUP IPPROTO_PUP IPPROTO_UDP = 17, /* User Datagram Protocol */ #define IPPROTO_UDP IPPROTO_UDP IPPROTO_IDP = 22, /* XNS IDP protocol */ #define IPPROTO_IDP IPPROTO_IDP IPPROTO_TP = 29, /* SO Transport Protocol Class 4 */ #define IPPROTO_TP IPPROTO_TP IPPROTO_DCCP = 33, /* Datagram Congestion Control Protocol */ #define IPPROTO_DCCP IPPROTO_DCCP IPPROTO_IPV6 = 41, /* IPv6-in-IPv4 tunnelling */ #define IPPROTO_IPV6 IPPROTO_IPV6 IPPROTO_RSVP = 46, /* RSVP Protocol */ #define IPPROTO_RSVP IPPROTO_RSVP IPPROTO_GRE = 47, /* Cisco GRE tunnels (rfc 1701,1702) */ #define IPPROTO_GRE IPPROTO_GRE IPPROTO_ESP = 50, /* Encapsulation Security Payload protocol */ #define IPPROTO_ESP IPPROTO_ESP IPPROTO_AH = 51, /* Authentication Header protocol */ #define IPPROTO_AH IPPROTO_AH IPPROTO_MTP = 92, /* Multicast Transport Protocol */ #define IPPROTO_MTP IPPROTO_MTP IPPROTO_BEETPH = 94, /* IP option pseudo header for BEET */ #define IPPROTO_BEETPH IPPROTO_BEETPH IPPROTO_ENCAP = 98, /* Encapsulation Header */ #define IPPROTO_ENCAP IPPROTO_ENCAP IPPROTO_PIM = 103, /* Protocol Independent Multicast */ #define IPPROTO_PIM IPPROTO_PIM IPPROTO_COMP = 108, /* Compression Header Protocol */ #define IPPROTO_COMP IPPROTO_COMP IPPROTO_SCTP = 132, /* Stream Control Transport Protocol */ #define IPPROTO_SCTP IPPROTO_SCTP IPPROTO_UDPLITE = 136, /* UDP-Lite (RFC 3828) */ #define IPPROTO_UDPLITE IPPROTO_UDPLITE IPPROTO_MPLS = 137, /* MPLS in IP (RFC 4023) */ #define IPPROTO_MPLS IPPROTO_MPLS IPPROTO_ETHERNET = 143, /* Ethernet-within-IPv6 Encapsulation */ #define IPPROTO_ETHERNET IPPROTO_ETHERNET IPPROTO_RAW = 255, /* Raw IP packets */ #define IPPROTO_RAW IPPROTO_RAW IPPROTO_MPTCP = 262, /* Multipath TCP connection */ #define IPPROTO_MPTCP IPPROTO_MPTCP IPPROTO_MAX };