VC++之网络编程二 Socket

 二 socket

1.基于TCP(面向连接)的socket编程

服务器端程序:

1.创建套接字(socket).

2.将套接字绑定到一个本地地址和端口上(bind).

3.将套接字设为监听模式,准备接收客户请求(listen).

4.等待客户请求到来;当请求到来后,接受连接请求,返回一个新的对应于此次连接的套接字(accept).

5.用返回的套按字和客户端进行通信(send/recv).

6.返回,等待另一个客户请求.

7.关闭套按字.

客户端程序:

1.创建套接字(socket).

2.向服务器发出连接请求(connect).

3.和服务器端进行通信(send/recv).

4.关闭套接字.

2.基于UDP(面向无连接)的socket编程

服务器端:

1.创建套接字(socket).

2.将套接字绑定到一个本地地址和端口上(bind).

3.等待接收数据(recvfrom).

4.关闭套接字.

客户端:

1.创建套接字(socket).

2.向服务器发送数据(sendto).

3.关闭套接字.

3.项目实例

基于TCP(面向连接)的socket编程实例

1)相关函数

----------- 加载socket库 begin ---------------

WSAStartup---加载套接字库,套接字库的版本协商

MAKEWORD---通过同时指定值来创建一个WORD值

WSAData---用WSAStartup获取的版本信息填充在WSAData结构体中

LOBYTE---获取WORD低字节

HIBYTE---获取WORD高字节

WSACleanup---终止使用Winsock,释放资源

----------- 加载socket库 end ---------------

----------- 创建socket begin---------------

socket---创建一个套接字

----------- 创建socket end ---------------

----------- 绑定socket begin ---------------

bind---用一个套接字关联一个本地地址

sockaddr

sockaddr_in

in_addr

htonl---转换为一个u_long从主机字节序到TCP/IP网络字节序

htons---转换为一个u_short从主机字节序到TCP/IP网络字节序

----------- 绑定socket end ---------------

----------- socket监听 begin ---------------

listen---将套接字设定为监听模式,以监听连接请求

----------- socket监听 end ---------------

----------- 等待客户端连接请求 begin ---------------

accept---等待客户端连接请求

----------- 等待客户端连接请求 end ---------------

----------- 向客户端发送请求数据 begin ---------------

send---对连接的套接字发送请求的数据

inet_ntoa---接受in_addr类型参数,返回一个点分十进制格式的IP地址的字符串

----------- 向客户端发送请求数据 end ---------------

----------- 接收数据 begin ---------------

recv---从一个已连接的套接字或者一个绑定到未连接的套接字接收数据

----------- 接收数据 end ---------------

int WSAStartup(    //The WSAStartup function initiates use of the Winsock DLL by a process.

  WORD wVersionRequested,

  LPWSADATA lpWSAData   //[out] Pointer to the WSADATA structure that is to receive details of the Windows Sockets implementation. 

);

wVersionRequested:指定要加载的Winsock库的版本.高位字节指定库的副版本,低位字节指定主版本.可用MAKEWORD(x,y)(其中,x是低位字节(主版本),y是高位字节(副版本)(笔者注:原讲义在此处是:x是高位字节, y是低位字节,笔者参考MSDN Library-Visual Studio 2008 SP1 后作了修改))方便地获得wVersionRequested的正确值.

lpWSAData:是指向WSADATA结构的指针,WSADATA接收Windows Sockets 实现的详细信息.(WSAStartup用其加载的库版本有关的信息填在这个结构中)

成功调用WSAStartup后,在最后都对应一个WSACleanUp调用,以释放为应用程序分配的资源.

int  WSACleanup (void);   //The WSACleanup function terminates use of the Winsock 2 DLL (Ws2_32.dll).

WORD MAKEWORD(           //The MAKEWORD macro creates a WORD value by concatenating the specified values.

    BYTE bLow,                      //Specifies the low-order byte of the new value. 

    BYTE bHigh                      //Specifies the high-order byte of the new value. 

);

typedef struct WSAData {      //The WSADATA structure contains information about the Windows Sockets implementation.

  WORD wVersion;

  WORD wHighVersion;

  char szDescription[WSADESCRIPTION_LEN+1];

  char szSystemStatus[WSASYS_STATUS_LEN+1];

  unsigned short iMaxSockets;

  unsigned short iMaxUdpDg;

  char FAR* lpVendorInfo;

} WSADATA, *LPWSADATA; 

BYTE LOBYTE(    //The LOBYTE macro retrieves the low-order byte from the specified value. 

    WORD wValue

);

BYTE HIBYTE(    //The HIBYTE macro retrieves the high-order byte from the given 16-bit value. 

    WORD wValue

);

----------------------------------------------------

SOCKET socket(      //This function creates a socket that is bound to a specific service provider.

  int af,                    //[in] Address family specification. 

  int type,                //[in] Type specification for the new socket.  SOCK_STREAM | SOCK_DGRAM  | SOCK_RAW

  int protocol         //[in] Protocol to be used with the socket that is specific to the indicated address family.

);

the following list shows the possible value of protocol type :

IPPROTO_IP 

IPPROTO_IPV6 

IPPROTO_TCP 

IPPROTO_UDP 

SOL_SOCKET 

AF_INET             //The AF_INET address family is the address family for IPv4.

--------------------------------------

int bind(           //This function associates a local address with a socket.

  SOCKET s,

  const struct sockaddr FAR* name,

  int namelen

);

struct sockaddr {                     //The sockaddr structure varies depending on the protocol selected.

                                                   //Except for the sin*_family parameter, sockaddr contents are expressed in network byte order.

  u_short sa_family;

  char sa_data[14];

};

sockaddr 结构体是为所有的地址家族准备的,通常会随所使用的网络协议不同而不同,会用其它相关结构体来替换sockaddr这个结构体.

sa_data是一块内存区,用来放置与协议相关的具体地址信息.对不同的协议家族,必须用来同的结构体来替换sockaddr.在TCP/IP协议家族中,可以用sockaddr_in来替换sockaddr.

struct sockaddr_in {    //In the Internet address family, this structure is used by Windows Sockets to specify a local or remote endpoint

                                       // address to which to connect a socket. This is the form of the sockaddr structure specific to the Internet

                                       // address family and can be cast to sockaddr. 

        short   sin_family;     //Address family; must be AF_INET. 

        u_short sin_port;      //Internet Protocol (IP) port. 

        struct  in_addr sin_addr;      //IP address in network byte order. 

        char    sin_zero[8];        //Padding to make structure the same size as SOCKADDR. 

};

sockaddr_in如果调用成功,则返回0,调用不成功,则返回SOCKET_ERROR,可用WSAGetLastError函数取得错误信息.

typedef struct in_addr {    //The in_addr structure represents an IPv4 Internet address.

union {    

struct {   u_char s_b1,s_b2,s_b3,s_b4;    } S_un_b;      //An IPv4 address formatted as four u_chars.

struct {   u_short s_w1,s_w2;    } S_un_w;        //An IPv4 address formatted as two u_shorts.

u_long S_addr;        //An IPv4 address formatted as a u_long.

} S_un;

} IN_ADDR,  *PIN_ADDR,  FAR *LPIN_ADDR;

将IP地址指定为INADDR_ANY,允许一个独立应用接受发自多个接口的回应.

u_long htonl(      //The htonl function converts a u_long from host to TCP/IP network byte order (which is big endian).

  __in  u_long hostlong

);

u_short htons(    //The htons function converts a u_short from host to TCP/IP network byte order (which is big-endian).

  __in  u_short hostshort

);

--------------------------

int listen(    //This function places a socket at a state where it is listening for an incoming connection.

  SOCKET s,

  int backlog    //等待连接的最大长度

);

--------------------------

SOCKET accept(    //This function permits an incoming connection attempt on a socket.

  SOCKET s,

  struct sockaddr FAR* addr,   //save IP address and port of clients

  int FAR* addrlen

);

----------------------------

int send(    //This function sends data on a connected socket.

  SOCKET s,

  const char FAR* buf,

  int len,

  int flags

);

char* FAR inet_ntoa(    //The inet_ntoa function converts an (Ipv4) Internet network address

                                         // into a string in Internet standard dotted-decimal format.

  __in  struct   in_addr in

);

---------------------------------

int recv(    //The recv function receives data from a connected socket or a bound connectionless socket.

  __in   SOCKET s,

  __out  char* buf,

  __in   int len,

  __in   int flags

);