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WinSock provides many socket functions, which do not represent a certain level of the protocol, but are essentially a set of programming interfaces that users can easily program with.

(1) socket function

The socket function is used to create a socket.

Syntax:

SOCKET socket (int af, int type, int protocol)

Af: identifies a family of addresses, usually AF_INET.

Type: identifies the socket type, SOCK_STREAM for streaming sockets, and SOCK_DGRAM for Datagram sockets.

Protocol: identifies that a particular protocol is used for this socket, usually 0, indicating that the default TCP/IP protocol is used.

(2) accpet function

The accpet function is used to accept connection requests from the client. The return value is a new socket that corresponds to the accepted client connection, which should be used for all subsequent operations of the client.

Syntax:

SOCKET accept (SOCKET scentstruct sockaddr FAR* addr, int FAR* addrlen)

S: is a socket that should be in the listening state.

Addr: a pointer to a sockaddr_in structure that contains a set of client port numbers, IP addresses, and so on.

Addrlen: the length used to receive the parameter addr.

(3) bind function

The bind function is used to bind a socket to a known address. If the function executes successfully, the return value is 0, otherwise it is SOCKET_ERROR.

Syntax:

Int bind (SOCKET s, const struct sockaddr FAR* name, int namelen)

S: is a socket.

Name: is a pointer to a sockaddr structure that contains the address and port number to bind.

Namelen: determines the length of the name buffer.

After defining a socket, you need to call the bind function to specify the native address, protocol, and port number for it.

For example, create a socket s and bind it to port 3010 with the following code:

Int port = 3010 parent s = socket (AF_INET,SOCK_STREAM,IPPROTO_IP); sockaddr_in addr;addr.sin_family = AF_INET; / / Internal network protocol TCP\ UDP and other addr.sin_port = htons (port); / / Port number addr.sin_addr.s_addr = htonl (INADDR_ANY); if (bind (s, (LPSOCKADDR) & addr,sizeof (addr)) = = 0) {MessageBox ("success");}

(4) closesocket function

The closesocket function closes a socket.

Syntax:

Int closesocket (SOCKET s)

S: identifies a socket. If the parameter s is set with the SO_DONTLINGER option, it will be returned immediately after the function is called, but if any data has not been transferred yet, the data will continue to be passed before closing the socket.

(5) connect function

The connect function sends a connection request. If the function executes successfully, the return value is 0, otherwise it is SOCKET_ERROR. Users can get their error description through WSAGetLastError.

Syntax:

Int connect (SOCKET SJ Const struct sockaddr FAR* name, int namelen)

S: identifies a socket.

Name: the host address and port number to which socket s wants to connect.

The length of the namelen:name buffer.

(6) htons function

The htons function converts a 16-bit unsigned short integer data from host arrangement to network arrangement.

Syntax:

U_short htons (u_short hostshort)

Hostshort: an unsigned short integer data arranged by the host.

(7) htonl function

The htonl function converts a 32-bit unsigned long integer data from host arrangement to network arrangement.

Syntax:

U_long htonl (u_long hostlong)

Hostlong: an unsigned long integer data arranged by the host.

(8) inet_addr function

The inet_addr function converts an address represented by a string into 32-bit unsigned long integer data.

Syntax:

Unsigned long inet_addr (const char FAR * cp)

Cp: a string that represents an IP address.

(9) listen function

The listen function is used to put sockets into listening mode.

Syntax:

Int listen (SOCKET s, int backlog)

S: socket.

Backlog: represents the maximum queue length waiting for a connection. For example, if backlog is set to 3 and four clients make connection requests at the same time, the first three client connections will be placed in the waiting queue and the fourth client will get an error message.

(10) recv function

The recv function is used to return data from the connected socket.

Syntax:

Int recv (SOCKET s, char FAR* buf, int len, int flags)

The parameters of the recv function are described in Table 18.5.

Table 18.5 description of recv function parameters

Parameter name parameter description

S identifies a socket

Buf is the buffer that receives data

Len is the length of buf

Flags indicates how the function is called. Available values are as follows: MSG_PEEK_ is used to view the incoming data. A copy of the data at the front of the sequence will be copied into the return buffer, but this data will not be removed from the sequence and used to process Out-Of-Band data.

(11) select function

The select function is used to check whether one or more sockets are in a readable, writable, or error state.

Syntax:

Int select (int nfds, fd_set FAR * readfds, fd_set FAR * writefds, fd_set FAR * exceptfds, const struct timeval FAR * timeout)

The parameters of the select function are described in Table 18.6.

Table 18.6 description of select function parameters

Parameter name parameter description

Nfds has no practical meaning, just to be compatible with sockets under UNIX

Readfds identifies a set of sockets that are checked and readable

Writefds identifies a set of writeable sockets that are checked

Exceptfds is a socket that is checked for errors

Timeout identifies the waiting time of the function

(12) send function

The send function sends data on a socket that has established a connection.

Syntax:

Int send (SOCKET s, const char FAR * buf, int len, int flags)

The parameters of the send function are described in Table 18.7.

Table 18.7 description of send function parameters

Parameter name parameter description

S identifies a socket

Buf is the buffer where the data to be sent is stored

Len identity buffer length

Flags identifies how the function is called

(13) WSAStartup function

The WSAStartup function is used to initialize the WS2_32 dynamic library. It should be the first Windows Socket function called by the application to determine the version used by Windows Socket.

Syntax:

Int WSAStartup (WORD wVersionRequested, LPWSADATA lpWSAData)

WVersionRequested: identifies the version of Windows Socket used by the caller, the revised version of the high-byte record, and the major version of the low-byte record. For example, if the version of Windows Socket is 2.1, then the high byte record 1 and the low byte record 2.

LpWSAData: record the details of Windows Socket.

The following code is used to determine the version used by Windows Socket.

WSADATA wsd;WSAStartup (MAKEWORD (2) & wsd)

14) WSACleanup function

The WSACleanup function is relative to the WSAStartup function and is used to terminate the use of the WS2_32 dynamic library.

Syntax:

Int WSACleanup (void)

(15) WSAAsyncSelect function

The WSAAsyncSelect function is used to associate events that occur on the network to a message in the window.

Syntax:

Int WSAAsyncSelect (SOCKET s, HWND hWnd, unsigned int wMsg, long lEvent)

The parameters of the WSAAsyncSelect function are described in Table 18.8.

Table 18.8 description of WSAAsyncSelect function parameters

Parameter name parameter description

S identity socket

HWnd identity window handle

WMsg identity window message

LEvent identifies events in the network

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