window_c++_socket編程_winsock2.h

1.初始化動態鏈接庫

WSAStartup: The WSAStartup function initiates use of the Winsock DLL by a process.

WSAStartup函數使用一個進程來初始化Winsock動態鏈接庫ws2_32.dll。

int WSAAPI WSAStartup(
  WORD      wVersionRequested,  //用於協商winsock dll的最高版本
  LPWSADATA lpWSAData  
　　//指向WSADATA數據結構的指針，該結構用於接收Windows套接字實現的詳細信息
);

初始化成功返回0，否則返回錯誤碼。

WSAStartup函數必須是應用程序或DLL調用的第一個Windows套接字函數。它允許應用程序或DLL指定所需的Windows套接字版本，並檢索特定Windows套接字實現的詳細信息。應用程序或DLL只能在成功調用WSAStartup后再發出Windows套接字函數。

int SocketInit()
{
    WORD wVersionRequested; //用 2 bytes 的字來表示
    WSADATA wsaData;
    int err;
    wVersionRequested = MAKEWORD(2, 2);  //DLL版本
    err = WSAStartup(wVersionRequested, &wsaData);
    if (err != 0)
    {
        printf("WinSock DLL版本不足要求\n");
        return 0;
    }
    if (LOBYTE(wsaData.wVersion) != 2 ||
        HIBYTE(wsaData.wVersion) != 2)
    {
        WSACleanup();
        return 0;
    }
    return 1;
}

其中WORD類型是微軟SDK中的類型，WORD的意思為字，是2byte的無符號整數，表示范圍0~65535.

2.創建socket

socket：The socket function creates a socket that is bound to a specific transport service provider.

SOCKET WSAAPI socket(
  int af, //地址族規范。地址族的可能值在Winsock2.h頭文件中定義。
  int type,
  int protocol
);

af:

在Windows Vista及以后發布的Windows SDK中，頭文件的組織發生了變化，地址族的可能值在Ws2def.h頭文件中定義。注意，Ws2def.h頭文件自動包含在Winsock2.h，不應該直接使用。

當前支持的值是AF_INET或AF_INET6，它們是IPv4和IPv6的Internet地址族格式。如果安裝了地址族的Windows套接字服務提供者，則支持地址族的其他選項(例如，與NetBIOS一起使用的AF_NETBIOS)。注意，AF_地址族和PF_協議族常量的值是相同的(例如，AF_INET和PF_INET)，因此可以使用任意一個常量。

type:

新套接字的類型規范。

套接字類型的可能值在Winsock2.h頭文件中定義。

SOCK_STREAM　　1　　

A socket type that provides sequenced, reliable, two-way, connection-based byte streams with an OOB data transmission mechanism. This socket type uses the Transmission Control Protocol (TCP) for the Internet address family (AF_INET or AF_INET6).

SOCK_DGRAM2　　2

A socket type that supports datagrams, which are connectionless, unreliable buffers of a fixed (typically small) maximum length. This socket type uses the User Datagram Protocol (UDP) for the Internet address family (AF_INET or AF_INET6).

......

protocol: 協議類型。

 

返回值：If no error occurs, socket returns a descriptor referencing the new socket. Otherwise, a value of INVALID_SOCKET is returned, and a specific error code can be retrieved by calling WSAGetLastError.

3.SOCKADDR_IN

typedef struct sockaddr_in {
  short          sin_family;
  u_short        sin_port;
  struct in_addr sin_addr;
  char           sin_zero[8];
} SOCKADDR_IN, *PSOCKADDR_IN, *LPSOCKADDR_IN;

4.connect

The connect function establishes a connection to a specified socket.

int WSAAPI connect(
  SOCKET         s,  //A descriptor identifying an unconnected socket.
  const sockaddr *name,  //A pointer to the sockaddr structure to which the connection should be established.
  int            namelen //The length, in bytes, of the sockaddr structure pointed to by the name parameter.
);

if (SOCKET_ERROR == SocketInit())
        return -1;

SOCKET sockClient = socket(AF_INET, SOCK_STREAM, 0);
SOCKADDR_IN addrSrv;
//addrSrv.sin_addr.S_un.S_addr = inet_pton(SeverIp);
inet_pton(AF_INET, SeverIp, &addrSrv.sin_addr); //設置addrSrv的ip
addrSrv.sin_family = AF_INET;
addrSrv.sin_port = htons(6666);  
//設置端口號，convert an IP port number in host byte order to the IP port number in network byte order
connect(sockClient, (SOCKADDR*)&addrSrv, sizeof(SOCKADDR)); //客戶端連接服務器