• 03.UDP套接字与原始套接字

    UDP套接字

    注意在UDP套接字中，要使用recvfrom和sendto

    • API:

      • recvfrom：

        接收数据包，并存储源地址（UDP）

      • 函数原型：

        int WSAAPI recvfrom(
  [in]                SOCKET   s,
  [out]               char     *buf,
  [in]                int      len,
  [in]                int      flags,
  [out]               sockaddr *from,
  [in, out, optional] int      *fromlen
);

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      • 参数：

        • s：标识绑定套接字的描述符
        • buf：传入数据的缓冲区
        • len：缓冲区长度
        • flags：用于修改函数调用行为
        • from：指向sockaddr结构的指针，该缓冲区中将保留源地址
        • fromlen：from指向的缓冲区大小

      • 返回值：

        如果未发生错误，recvfrom函数将返回收到的字节数

    • UDP Server：

      #define _WINSOCK_DEPRECATED_NO_WARNINGS
#include 
#include 
#pragma comment(lib,"ws2_32.lib")

int main() {
	WORD wVersionRequested = MAKEWORD(2, 2);
	WSAData lpWSAData;
	if (WSAStartup(wVersionRequested, &lpWSAData)) {
		std::cout << "WSAStartup Error!" << std::endl;
		return -1;
	}

	//SOCKADDR_IN结构用于指定AF_INET地址系列的传输地址和端口
	sockaddr_in saddr;
	saddr.sin_addr.S_un.S_addr = htonl(INADDR_ANY);
	saddr.sin_family = AF_INET;
	saddr.sin_port = htons(50123);

	SOCKET sock = socket(AF_INET, SOCK_DGRAM, 0);
	if (sock < 0) {
		return -1;
	}
	char opt;
	setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

	int nRet = bind(sock, (sockaddr*)&saddr, sizeof(saddr));

	sockaddr_in raddr;
	int nLength = sizeof(sockaddr);
	char szReadBuffer[50]{ 0 };
	while (true) {
		nRet = recvfrom(sock, szReadBuffer, 50, 0, (sockaddr*)&raddr, &nLength);
		if (nRet < 0) {
			return -1;
		}
		std::cout << "data:" << szReadBuffer << std::endl;
		std::cout << "请输入：";
		char szBuffer[50]{ 0 };
		std::cin >> szBuffer;
		sendto(sock, szBuffer, strlen(szBuffer), 0, (sockaddr*)&raddr, sizeof(sockaddr));
	}
	WSACleanup();
	system("pause");
	return 0;
}

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    • UDP Client：

      #define _WINSOCK_DEPRECATED_NO_WARNINGS
#include 
#include 
#pragma comment(lib,"ws2_32.lib")

int main() {

	WORD wVersionRequested = MAKEWORD(2, 2);
	WSAData lpWSAData;
	WSAStartup(wVersionRequested, &lpWSAData);

	sockaddr_in saddr;
	saddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
	saddr.sin_family = AF_INET;
	saddr.sin_port = htons(50123);

	SOCKET SocClient = socket(AF_INET, SOCK_DGRAM, 0);
	if (SocClient < 0) {
		return -1;
	}

	char opt;
	setsockopt(SocClient, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

	char szSendBuffer[50]{ 0 };
	char szReadBuffer[50]{ 0 };
	sockaddr_in raddr;
	int nLength = sizeof(raddr);
	while (true) {
		std::cout << "请输入：";
		std::cin >> szSendBuffer;
		sendto(SocClient, szSendBuffer, strlen(szSendBuffer), 0, (sockaddr*)&saddr, sizeof(sockaddr));
		recvfrom(SocClient, szReadBuffer, 50, 0, (sockaddr*)&raddr, &nLength);
		std::cout << "Server:" << szReadBuffer << std::endl;
	}
	closesocket(SocClient);
	WSACleanup();
	system("pause");
	return 0;
}

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    原始套接字

    • 服务端：
      #define _WINSOCK_DEPRECATED_NO_WARNINGS
#include 
#include 
#pragma comment(lib,"ws2_32.lib")

typedef struct _IP_HEADER {
	//版本信息,首部长度
	char cVersionAndHeaderLen;
	//服务类型
	char vTypeOfServer;
	//数据包长度
	short sTotalLenOfPacket;
	//数据包ID
	short sPacketID;
	//分片信息
	short sSliceinfp;
	//生存时间
	char cTTL;
	//协议类型
	char cTypeOfProtocol;
	//首部校验和
	short sCheckSum;
	//源IP地址
	unsigned int uiSrcIP;
	//目的IP地址
	unsigned int uiDestIP;
}IP_HEADER, *pIP_HEADER;

typedef struct _UDP_HEADER {
	//源端口号
	unsigned short usSourPort;
	//目的端口号
	unsigned short usDestIPPort;
	//数据包长度
	unsigned short usLength;
	//校验和
	unsigned short usCheckSum;
}UDP_HEADER, pUDP_HEADER;

int main() {
	WORD wVersionRequested = MAKEWORD(2, 2);
	WSAData lpWSAData;
	WSAStartup(wVersionRequested, &lpWSAData);

	sockaddr_in SAddr;
	SAddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
	SAddr.sin_family = AF_INET;
	SAddr.sin_port = htons(50123);
	
	SOCKET SocSrv = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
	if (SocSrv < 0) {
		return -1;
	}

	char opt;
	setsockopt(SocSrv, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

	int nRet = bind(SocSrv, (sockaddr*)&SAddr, sizeof(SAddr));
	if (nRet < 0) {
		return -1;
	}

	char szReadBuffer[500]{ 0 };
	sockaddr_in raddr;
	int nLength = sizeof(sockaddr);
	while (true) {
		std::cout << "waiting......" << std::endl;
		nRet = recvfrom(SocSrv, szReadBuffer, 500, 0, (sockaddr*)&raddr, &nLength);
		IP_HEADER iph;
		UDP_HEADER udph;
		memcpy(&iph, szReadBuffer, 20);
		memcpy(&udph, szReadBuffer + 20, 8);
		int srcp = ntohs(udph.usSourPort);
		in_addr ias, iad;
		ias.s_addr = iph.uiSrcIP;
		iad.s_addr = iph.uiDestIP;
		char Temp[0x100]{ 0 };
		strcpy_s(Temp, inet_ntoa(iad));
		std::cout << "SrcIP:" << inet_ntoa(iad) << "  Port:" << ntohs(udph.usSourPort) << std::endl;
		std::cout << "DestIP:" << inet_ntoa(iad) << "  Port:" << ntohs(udph.usDestIPPort) << std::endl;
		std::cout << "recv data:" << szReadBuffer + 28 << std::endl;
	}
	closesocket(SocSrv);
	WSACleanup();
	system("pause");
	return 0;
}

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    • 客户端：
      #define _WINSOCK_DEPRECATED_NO_WARNINGS
#include 
#include 
#pragma comment(lib,"ws2_32.lib")

int main() {

	WORD wVerSionRequested = MAKEWORD(2, 2);
	WSAData lpWSAData;
	WSAStartup(wVerSionRequested, &lpWSAData);

	sockaddr_in saddr;
	saddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
	saddr.sin_family = AF_INET;
	saddr.sin_port = htons(50123);
	
	SOCKET SocClient = socket(AF_INET, SOCK_DGRAM, 0);
	if (SocClient < 0) {
		return -1;
	}

	char opt;
	setsockopt(SocClient, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

	char szSendBuffer[500]{ 0 };
	std::cout << "input:";
	std::cin >> szSendBuffer;
	sendto(SocClient, szSendBuffer, strlen(szSendBuffer), 0, (sockaddr*)&s5addr, sizeof(sockaddr));	WSACleanup();
	closesocket(SocClient);
	WSACleanup();
	system("pause");
	return 0;
}

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  • 原文地址：https://blog.csdn.net/qq_73985089/article/details/134294683