[网络协议]UDP广播

服务端

#define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <WS2tcpip.h>
#include <WinSock2.h>
#include <iostream>
using namespace std;
#pragma comment(lib,"ws2_32.lib")

int main()
{
	WSADATA wsaData = {0};
	WSAStartup(MAKEWORD(2, 2), &wsaData);
	SOCKET serverSocket = socket(AF_INET, SOCK_DGRAM, 0);
	//设置套接字可以发送广播消息权限
	bool optval = true;
	setsockopt(serverSocket, SOL_SOCKET, SO_BROADCAST, (char*)&optval, sizeof(optval));		
	//SOCKADDR_IN serverSockAddr_in = { 0 };
	//serverSockAddr_in.sin_family = AF_INET;
	//serverSockAddr_in.sin_addr.S_un.S_addr = INADDR_ANY;
	//serverSockAddr_in.sin_port = htons(6666);
	//setsockopt(serverSocket, SOL_SOCKET, SO_REUSEADDR, (char*)&optval, sizeof(optval));
	//bind(serverSocket, (SOCKADDR*)&serverSockAddr_in, sizeof(serverSockAddr_in));				//不需要接收消息就不需要绑定了

	//要发送的广播地址
	SOCKADDR_IN broadcastSockAddr_in = { 0 };
	broadcastSockAddr_in.sin_family = AF_INET;
	broadcastSockAddr_in.sin_addr.S_un.S_addr = INADDR_BROADCAST; // inet_addr("172.16.20.255");	本地广播地址/直接广播地址
	broadcastSockAddr_in.sin_port = htons(6666);
	

	while (true)
	{
		cout << "输入内容：";
		char sendStr[100] = { 0 };
		cin >> sendStr;
		sendto(serverSocket, sendStr, sizeof(sendStr) - 1, 0, (SOCKADDR*)&broadcastSockAddr_in, sizeof(broadcastSockAddr_in));
		//也可以自己发自己收（广播程序正常为服务端只负责发，客户端只负责收）
		//char recvStr[100] = { 0 };
		//recvfrom(serverSocket, recvStr, sizeof(recvStr)-1, 0,0,0);
		//cout << "收到消息:" << recvStr << endl;
		
	}
	return 0;
}

客户端

#define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <WS2tcpip.h>
#include <WinSock2.h>
#include <iostream>
using namespace std;
#pragma comment(lib,"ws2_32.lib")

int main()
{
	WSADATA wsaData = { 0 };
	WSAStartup(MAKEWORD(2, 2), &wsaData);
	SOCKET clientSocket = socket(AF_INET, SOCK_DGRAM, 0);
	SOCKADDR_IN clientSockAddr_in = { 0 };
	clientSockAddr_in.sin_family = AF_INET;
	clientSockAddr_in.sin_addr.S_un.S_addr =  INADDR_ANY;
	clientSockAddr_in.sin_port = htons(6666);
	bool optval = true;
	setsockopt(clientSocket, SOL_SOCKET, SO_REUSEADDR, (char*)&optval, sizeof(optval));				//设置端口重用（非必要）
	int bindRet = bind(clientSocket, (SOCKADDR*)&clientSockAddr_in, sizeof(clientSockAddr_in));	//显式绑定套接字用于消息
	if (bindRet == SOCKET_ERROR)
	{
		cout << "绑定套接字失败\n";
		closesocket(clientSocket);
		WSACleanup();
		system("pause");
		return 0;
	}
	while (true)
	{
		char recvStr[100] = { 0 };
		SOCKADDR_IN fromSockAddr_in = { 0 };
		int len = sizeof(fromSockAddr_in);
		recvfrom(clientSocket, recvStr, sizeof(recvStr) - 1, 0, (SOCKADDR*)&fromSockAddr_in, &len);
		std::cout << "(" << inet_ntoa(fromSockAddr_in.sin_addr) << ":" << ntohs(fromSockAddr_in.sin_port) << ")：" << recvStr << std::endl;
	}
	return 0;
}