常用类型的定义：
（以下定义从Winsock2.h文件中截取）
/*
* The new type to be used in all
* instances which refer to sockets.
*/
typedef UINT_PTR SOCKET;//SOCKET原来就是一个unsigned int的指针而已
/*
* Select uses arrays of SOCKETs. These macros manipulate such
* arrays. FD_SETSIZE may be defined by the user before including
* this file, but the default here should be >= 64.
*
* CAVEAT IMPLEMENTOR and USER: THESE MACROS AND TYPES MUST BE
* INCLUDED IN WINSOCK2.H EXACTLY AS SHOWN HERE.
*/
#ifndef FD_SETSIZE
#define FD_SETSIZE 64
#endif /* FD_SETSIZE */
typedef struct fd_set {
u_int fd_count; /* how many are SET? */
SOCKET fd_array[FD_SETSIZE]; /* an array of SOCKETs */
} fd_set;//fd_set是用来select的，表示一个集合，STL中不是有个模板类set么
//对fd_set结构，Winsock2.h中还定义了四个宏定义来操作fd_set
//FD_CLR(fd, set),FD_SET(fd, set),FD_ZERO(set),FD_ISSET(fd, set)
//一般用法是先定义一个fd_set,使用之前调用fd_zero，再将一个socket放到fd_set中
//经过一系列操作后，用fd_isset判断某个socket是否还在set中。
//SOCKET fd;
//......
//fd_set ReadFds;
//FD_ZERO(&ReadFds);
//FD_SET(fd,&ReadFds);
//.....
//if ( FD_ISSET(fd,&ReadFds) )
//.....
/*
* Structure used in select() call, taken from the BSD file sys/time.h.
*/
struct timeval {
long tv_sec; /* seconds */
long tv_usec; /* and microseconds */
};//这个也是用于select函数中的，超时参数
struct hostent {//表示主机的结构
char FAR * h_name; /* official name of host */
char FAR * FAR * h_aliases; /* alias list */
short h_addrtype; /* host address type */
short h_length; /* length of address */
char FAR * FAR * h_addr_list; /* list of addresses */
#define h_addr h_addr_list[0] /* address, for backward compat */
};
/*
* Internet address (old style... should be updated)//晕，什么时候update？
*///原来每次看到in_addr结构都不知道为什么叫in_addr,原来是这样。。。
struct in_addr {
union {
struct { u_char s_b1,s_b2,s_b3,s_b4; } S_un_b;
struct { u_short s_w1,s_w2; } S_un_w;
u_long S_addr; //大部分都用这个变量就够了（一个ip地址32位刚好一个unsigned long）
} S_un;
#define s_addr S_un.S_addr //这样定义以后用的很方便，in_addr.s_addr就可以了。
/* can be used for most tcp & ip code */
#define s_host S_un.S_un_b.s_b2
/* host on imp */
#define s_net S_un.S_un_b.s_b1
/* network */
#define s_imp S_un.S_un_w.s_w2
/* imp */
#define s_impno S_un.S_un_b.s_b4
/* imp # */
#define s_lh S_un.S_un_b.s_b3
/* logical host */
};
//这b1，b2，b3，b4，w1，w2不知道有乜用，代表乜意思。。。
#endif
/*
* Socket address, internet style.
*/
struct sockaddr_in {
short sin_family;//地址家族一般都是AF_INET或者PF_INET
u_short sin_port;//端口
struct in_addr sin_addr;//ip地址
char sin_zero[8];
};
/*
* Structure used by kernel to store most//计算机内核中处理用的是这种表示
* addresses.
*/
struct sockaddr {
u_short sa_family; /* address family */
char sa_data[14]; /* up to 14 bytes of direct address */
};
//仔细算一下sockaddr_in和sockaddr两个结构的大小是一样，所以可以直接强制类型转换赋值
//比如accept函数其中一个参数类型struct sockaddr FAR * ，你如果有一个struct sockaddr_in myaddr
//就可以直接accept(..(struct sockaddr *)myaddr.....
/*
* WinSock 2 extension -- WSABUF and QOS struct, include qos.h
* to pull in FLOWSPEC and related definitions
*/
typedef struct _WSABUF {//缓冲区，一般ms在带WSA前缀的accept，receive，send等函数中才用到
u_long len; /* the length of the buffer */
char FAR * buf; /* the pointer to the buffer */
} WSABUF, FAR * LPWSABUF;
typedef struct WSAData {
WORD wVersion;
WORD wHighVersion;
#ifdef _WIN64
unsigned short iMaxSockets;
unsigned short iMaxUdpDg;
char FAR * lpVendorInfo;
char szDescription[WSADESCRIPTION_LEN+1];
char szSystemStatus[WSASYS_STATUS_LEN+1];
#else
char szDescription[WSADESCRIPTION_LEN+1];
char szSystemStatus[WSASYS_STATUS_LEN+1];
unsigned short iMaxSockets;
unsigned short iMaxUdpDg;
char FAR * lpVendorInfo;
#endif
} WSADATA, FAR * LPWSADATA;//其实这个结构不需要怎么了解，因为它在用的很少，就是在调用WSAStartup才用到一次
/*
* Address families.
*/
#define AF_UNSPEC 0 /* unspecified */
/*
* Although AF_UNSPEC is defined for backwards compatibility, using
* AF_UNSPEC for the "af" parameter when creating a socket is STRONGLY
* DISCOURAGED. The interpretation of the "protocol" parameter
* depends on the actual address family chosen. As environments grow
* to include more and more address families that use overlapping
* protocol values there is more and more chance of choosing an
* undesired address family when AF_UNSPEC is used.
*/
#define AF_UNIX 1 /* local to host (pipes, portals) */
#define AF_INET 2 /* internetwork: UDP, TCP, etc. */
#define AF_IMPLINK 3 /* arpanet imp addresses */
#define AF_PUP 4 /* pup protocols: e.g. BSP */
#define AF_CHAOS 5 /* mit CHAOS protocols */
#define AF_NS 6 /* XEROX NS protocols */
#define AF_IPX AF_NS /* IPX protocols: IPX, SPX, etc. */
#define AF_ISO 7 /* ISO protocols */
#define AF_OSI AF_ISO /* OSI is ISO */
#define AF_ECMA 8 /* european computer manufacturers */
#define AF_DATAKIT 9 /* datakit protocols */
#define AF_CCITT 10 /* CCITT protocols, X.25 etc */
#define AF_SNA 11 /* IBM SNA */
#define AF_DECnet 12 /* DECnet */
#define AF_DLI 13 /* Direct data link interface */
#define AF_LAT 14 /* LAT */
#define AF_HYLINK 15 /* NSC Hyperchannel */
#define AF_APPLETALK 16 /* AppleTalk */
#define AF_NETBIOS 17 /* NetBios-style addresses */
#define AF_VOICEVIEW 18 /* VoiceView */
#define AF_FIREFOX 19 /* Protocols from Firefox */
#define AF_UNKNOWN1 20 /* Somebody is using this! */
#define AF_BAN 21 /* Banyan */
#define AF_ATM 22 /* Native ATM Services */
#define AF_INET6 23 /* Internetwork Version 6 */
#define AF_CLUSTER 24 /* Microsoft Wolfpack */
#define AF_12844 25 /* IEEE 1284.4 WG AF */
#define AF_IRDA 26 /* IrDA */
#define AF_NETDES 28 /* Network Designers OSI & gateway
enabled protocols */
#define AF_TCNPROCESS 29
#define AF_TCNMESSAGE 30
#define AF_ICLFXBM 31
#define AF_MAX 32
/*
* Protocol families, same as address families for now.
*/
#define PF_UNSPEC AF_UNSPEC
#define PF_UNIX AF_UNIX
#define PF_INET AF_INET
#define PF_IMPLINK AF_IMPLINK
#define PF_PUP AF_PUP
#define PF_CHAOS AF_CHAOS
#define PF_NS AF_NS
#define PF_IPX AF_IPX
#define PF_ISO AF_ISO
#define PF_OSI AF_OSI
#define PF_ECMA AF_ECMA
#define PF_DATAKIT AF_DATAKIT
#define PF_CCITT AF_CCITT
#define PF_SNA AF_SNA
#define PF_DECnet AF_DECnet
#define PF_DLI AF_DLI
#define PF_LAT AF_LAT
#define PF_HYLINK AF_HYLINK
#define PF_APPLETALK AF_APPLETALK
#define PF_VOICEVIEW AF_VOICEVIEW
#define PF_FIREFOX AF_FIREFOX
#define PF_UNKNOWN1 AF_UNKNOWN1
#define PF_BAN AF_BAN
#define PF_ATM AF_ATM
#define PF_INET6 AF_INET6
#define PF_MAX AF_MAX
下面这些函数属于基本常用函数，下次学习
u_long htonl(u_long hostlong)
u_short htons(u_short hostshort)
u_long ntohl(u_long netlong)
u_short ntohs(u_short netshort)
unsigned long inet_addr(const char* cp);
int getpeername(SOCKET s,struct sockaddr* name,int* namelen);
int getsockname(SOCKET s,struct sockaddr* name,int* namelen);
char* FAR inet_ntoa(struct in_addr in);
struct HOSTENT* FAR gethostbyaddr(const char* addr,int len,int type);
struct hostent* FAR gethostbyname(const char* name);
int gethostname(char* name,int namelen);
int WSAGetLastError(void);
int WSAStartup(WORD wVersionRequested,LPWSADATA lpWSAData);
int ioctlsocket(SOCKET s,long cmd,u_long* argp);
int listen(SOCKET s,int backlog);
SOCKET accept(SOCKET s,struct sockaddr* addr,int* addrlen);
int send(SOCKET s,const char* buf,int len,int flags);
int recv(SOCKET s,char* buf,int len,int flags);