Basic knowledge of Windows Network Programming and basic knowledge of Network Programming

Basic knowledge of Windows Network Programming and basic knowledge of Network Programming

1. WinSock Initialization

# Include <iostream> # include <WinSock2.h> # include <MSWSock. h> # pragma comment (lib, "WS2_32.lib") // when using WinSock2.h, the using namespace std must be loaded; // The Winsock2 function carries the WSA prefix, except WSAStartup WSACleanup WSARecvEX WSAGetLastErrorint main () {WSADATA wsData; if (SOCKET_ERROR = WSAStartup (MAKEWORD (2, 2), & wsData )) // The first 2 is the minor version {cout <"initialization error! "<Endl ;}cout <" main version: "<(int) LOBYTE (wsData. wHighVersion) <endl; // cout <"minor version" <(int) HIBYTE (wsData. wHighVersion) <endl; WSACleanup (); system ("pause"); return-1 ;}

2. Check and handle errors

WSAGetLastErrorWSASetLastError manually sets the error code

3.

typedef struct sockaddr_in {    ADDRESS_FAMILY sin_family;    USHORT sin_port;    IN_ADDR sin_addr;    CHAR sin_zero[8];} SOCKADDR_IN, *PSOCKADDR_IN;

Sin_family must be AF_INET, which indicates that WinSock uses an IP address family.
Sin_zero [8] only acts as a fill item, so that SOCKADDR_IN and SOCKADDR have the same structure length. SOCKADDR is a common socket address and serves as void *.

Byte sorting
Different computer processors may be encoded in the form of big-endian or little-endian. The multi-byte value specified by Internet standards must be expressed in the big-endian format, which is generally called the network byte sequence.
The following four common API functions convert the number of bytes from the host to the network byte order:

WSAHtonl // 4-byte htonlWSAHtons // 2-byte htons

Otherwise

WSANtohlntohlWSANtohsntohs

Another common function is to convert the IP address to a 4-byte integer.
SrvAddr. sin_addr.S_un.S_addr = inet_addr ("127.0.0.1 ");

SOCKADDR_IN srvAddr;srvAddr.sin_addr.S_un.S_addr = htonl(INADDR_ANY);srvAddr.sin_family = AF_INET;srvAddr.sin_port = htons(DefaultPort);

INADDR_ANY indicates all the ports sent to the server. No matter which network adapter/IP address receives the data, it is handed over to the socket for processing.