Introduction to network programming of windows core programming

Source: WeChat Official Account "Programming Learning Base"

Big end little end

Big-endian mode :指数据的高字节保存在内存的低地址

For example: the storage order of 12345 (0x3039) is 0x30、0x39

Little endian mode :指数据的高字节保存在内存的高地址

For example: the storage order of 12345 (0x3039) is 0x39、0x30

Judge the big end

method one:

#include<stdio.h>
int main(int argc, char *argv[])
{
    
    
	int i = 0x12345678;
	char c = i;
	if (c == 0x78)
	{
    
    
		printf("小端\n");
	}
	else
	{
    
    
		printf("大端\n");
	}
	return 0;
}

Method Two:

#include<stdio.h>
int main(void)
{
    
    
	int  a = 0x12345678;
	char *p = (char *)&a;
	if (0x78 == *p)
	{
    
    
		printf("小端\n");
	}
	else
	{
    
    
		printf("大端\n");
	}
	return 0;
}

Method three:

#include<stdio.h>
typedef union NODE
{
    
    
	int i;
	char c;
}Node;
int main(int argc, char *argv[])
{
    
    
	Node node;
	node.i = 0x12345678;
	if (0x78 == node.c)
	{
    
    
		printf("小端\n");
	}
	else
	{
    
    
		printf("大端\n");
	}
	return 0;
}

CS model

Socket network programming

WSAStartup / WSACleanup

int WSAStartup ( WORD wVersionRequested,
                LPWSADATA pWSAData );

Each one WSAStartupis not allowed to correspond to one WSACleanupcall

socket

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

• af: AF_INET、AF_INET6、AF_LOCAL

WinSock only supportsAF_INET

• type:

SOCK_STREAM, SOCK_DGRAM, SOCK_RAWEtc.

• protocol:

If the type is SOCK_STREAM, the tcp protocol is used

If the type is SOCK_DGRAM, the udp protocol is used

It protocolcan be specified as 0 at this time

If the type is SOCK_RAW, the original socket is used, and the protocol can be customized, such as ICMP and other protocols

sockaddr_in

struct sockaddr_in {
    
     
　　 short int sin_family,		//地址家族
	unsigned short int sin_port, //端口号
    struct in_addr sin_addr,	//IP地址
    unsigned char sin_zero[8],	//空字节，设为0
}   

struct in_addr:

struct in_addr{
    
     
	unsigned long s_addr;
}

Dotted decimal conversion

inet_addr ()

将一个点分十进制字符串转化为二进制的数

in_addr_t inet_addr(const char* cp);

• Parameters: string, a dotted decimal IP address

• Return value:
  If the string is valid, the string is converted to a 32-bit binary network byte order IPV4 address; otherwise, it is INADDR_NONE

inet_ntoa ()

将二进制数转换为一个点分十进制字符串

char *inet_ntoa(struct in_addr);

• Parameters: in_addr is a structure used to represent a 32-bit IPV4 address
• Return value: Returns the pointer of the dotted decimal string in static memory

Port conversion function

The TCP/IP protocol uniformly uses the network byte order, that is, big endian

u_short htons(u_short hostshurt)	//主机字节顺序转网络字节顺序
u_long htonl(u_long hostshurt)		//主机字节顺序转网络字节顺序
u_short ntohs(u_short hostshurt)	//网络字节顺序转主机字节顺序
u_long ntohl(u_long hostshurt)		//网络字节顺序转主机字节顺序

Usually used htonsfor port conversion

bind

int bind(
	SOCKET s,						//套接字句柄
	onst struct sockaddr* name,		//本地地址
	int namelen						//地址长度
);　

listen

int listen(
	SOCKET s,		//套接字句柄
	int backlog		//监听队列允许保持的最大连接数量
);

accept

SOCKET accept(
	SOCKET s,			//套接字句柄
	struct sockaddr* addr,	//协议族渎职
	int* addrlen			//地址长度
);

connect

int connect(
	SOCKET s,	//套接字句柄
	const struct sockaddr* name,	//协议族地址
 	int namelen						//地址长度
);

tcp server

#include <winsock2.h>	// 为了使用Winsock API函数
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>

// 告诉连接器与WS2_32库连接
#pragma comment(lib,"WS2_32.lib")

int main(int argc, char* argv[])
{
    
    
	// 初始化WS2_32.dll
	WSADATA wsaData;
	WORD sockVersion = MAKEWORD(2, 2);
	WSAStartup(sockVersion, &wsaData);	//请求了一个2.2版本的socket

	// 创建套节字
	SOCKET s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (s == INVALID_SOCKET)
	{
    
    
		printf("Failed socket() \n");
		WSACleanup();
		return 0;
	}

	// 填充sockaddr_in结构
	sockaddr_in sin;
	sin.sin_family = AF_INET;				
	sin.sin_port = htons(8888);				//8888端口
	//sin.sin_addr.S_un.S_addr = INADDR_ANY;	//本地地址 
	sin.sin_addr.S_un.S_addr = inet_addr("169.254.211.52"); //172.19.12.44

	// 绑定这个套节字到一个本地地址
	if (bind(s, (LPSOCKADDR)&sin, sizeof(sin)) == SOCKET_ERROR)
	{
    
    
		printf("Failed bind() \n");
		WSACleanup();
		return 0;
	}

	// 进入监听模式
	if (listen(s, 2) == SOCKET_ERROR)		//最大连接数为2
	{
    
    
		printf("Failed listen()");
		WSACleanup();
		return 0;
	}
	printf("Start listen:\n");
	// 循环接受客户的连接请求
	sockaddr_in remoteAddr;
	int nAddrLen = sizeof(remoteAddr);
	SOCKET client;
	char szText[] = "hello！\n";
	while (TRUE)
	{
    
    
		// 接受一个新连接
		client = accept(s, (SOCKADDR*)&remoteAddr, &nAddrLen);
		if (client == INVALID_SOCKET)
		{
    
    
			printf("Failed accept()");
			continue;
		}

		printf(" 接受到一个连接：%s \r\n", inet_ntoa(remoteAddr.sin_addr));

		// 向客户端发送数据
		send(client, szText, strlen(szText), 0);

		// 关闭同客户端的连接
		closesocket(client);
	}

	// 关闭监听套节字
	closesocket(s);
	// 释放WS2_32库
	WSACleanup();

	return 0;
}

tcp client address

#include <winsock2.h>	
#include <stdio.h>
#include <windows.h>

// 告诉连接器与WS2_32库连接
#pragma comment(lib,"WS2_32.lib")

int main(int argc, char* argv[])
{
    
    
	// 初始化WS2_32.dll
	WSADATA wsaData;
	WORD sockVersion = MAKEWORD(2, 2);
	WSAStartup(sockVersion, &wsaData);

	// 创建套节字
	SOCKET s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (s == INVALID_SOCKET)
	{
    
    
		printf("Failed socket() \n");
		WSACleanup();
		return 0;
	}

	// 填写远程地址信息
	sockaddr_in servAddr;
	servAddr.sin_family = AF_INET;
	servAddr.sin_port = htons(8888);
	// 如果你的计算机没有联网，直接使用本地地址127.0.0.1
	servAddr.sin_addr.S_un.S_addr = inet_addr("169.254.211.52");

	if (connect(s, (sockaddr*)&servAddr, sizeof(servAddr)) == -1)
	{
    
    
		printf("Failed connect() \n");
		WSACleanup();
		return 0;
	}

	// 接收数据
	char buff[256];
	int nRecv = recv(s, buff, 256, 0);
	if (nRecv > 0)
	{
    
    
		buff[nRecv] = '\0';
		printf(" 接收到数据：%s", buff);
	}
    
	// 关闭套节字
	closesocket(s);
	// 释放WS2_32库
	WSACleanup();
	return 0;
}