弄清socket

1. 函数原型

int socket(int domain, int type, int protocol);

参数介绍：
domain

/* 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_SNA          22          /* Linux SNA Project ( */
#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_BLUETOOTH    31    /* Bluetooth sockets */
#define AF_MAX          32          /* For now.. */

/* Protocol families, same as address families. */

type:

enum sock_type {
        SOCK_STREAM = 1,    //stream (connection) socket
        SOCK_DGRAM = 2,     //datagram (conn.less) socket
        SOCK_RAW = 3,       //raw socket
        SOCK_RDM = 4,       //reliably-delivered message
        SOCK_SEQPACKET = 5, //sequential packet socket
        SOCK_PACKET = 10,   //linux specific way of getting packets at the dev level.For writing rarp and other similar things on the user level.
}

protocol

/* Standard well-defined IP protocols. */
enum {
  IPPROTO_IP = 0,         /* Dummy protocol for TCP */
  IPPROTO_ICMP = 1,       /* Internet Control Message Protocol */
  IPPROTO_IGMP = 2,       /* Internet Group Management Protocol */
  IPPROTO_IPIP = 4,       /* IPIP tunnels (older KA9Q tunnels use 94) */
  IPPROTO_TCP = 6,        /* Transmission Control Protocol */
  IPPROTO_EGP = 8,        /* Exterior Gateway Protocol */
  IPPROTO_PUP = 12,       /* PUP protocol */
  IPPROTO_UDP = 17,       /* User Datagram Protocol */
  IPPROTO_IDP = 22,       /* XNS IDP protocol */
  IPPROTO_RSVP = 46,      /* RSVP protocol */
  IPPROTO_GRE = 47,       /* Cisco GRE tunnels (rfc 1701,1702) */

  IPPROTO_IPV6 = 41,      /* IPv6-in-IPv4 tunnelling */

  IPPROTO_ESP = 50,       /* Encapsulation Security Payload protocol */
  IPPROTO_AH = 51,        /* Authentication Header protocol */
  IPPROTO_PIM = 103,      /* Protocol Independent Multicast */

  IPPROTO_COMP = 108,     /* Compression Header protocol */
  IPPROTO_SCTP = 132,     /* Stream Control Transport Protocol */

  IPPROTO_RAW = 255,      /* Raw IP packets */
  IPPROTO_MAX
};