UDP组播的c++实现

1 写socket的时候UDP和TCP的代码区别就是 是否有连接过程；有connect连接的代码的就是TCP，没有连接的就是UDP

以下代码是发送信息给组播地址（没有写接收代码。接收的代码就是要写个加入多播组，从多播组接收的逻辑）

参考：https://blog.csdn.net/zhizhengguan/article/details/109312144

// UDP_socket.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。
//

#include <stdio.h>
#include <stdlib.h>

#if defined(_WIN32)
#include <winsock2.h>
#include <ws2tcpip.h>
#include <iphlpapi.h>
#pragma comment (lib, "Ws2_32.lib")
#pragma comment(lib,"Iphlpapi.lib")
#else
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#endif // defined(_WIN32)

int main() {
    char group_addr[16] = "224.1.3.250";



    //初始化WinSock.否则socket(AF_INET, SOCK_DGRAM, 0)会一直返回-1

    WSADATA WSAData;

    if (WSAStartup(MAKEWORD(2, 0), &WSAData) != 0)

    {

        return FALSE;

    }

    int socked = ::socket(AF_INET, SOCK_DGRAM, 0);
    if (socked < 0)
    {
        perror("socket failed!");
        return 2;
    }

    struct sockaddr_in remote_addr;
    memset(&remote_addr, 0, sizeof(remote_addr));

    remote_addr.sin_family = AF_INET;
    inet_pton(AF_INET, group_addr, &remote_addr.sin_addr.s_addr);
    remote_addr.sin_port = htons(25666);

    char buf[200] = "1234567890";
    int length = 0;
    int i = 0;
    while (1)
    {
        i++;

        length = sendto(socked, buf, strlen(buf), 0, (struct sockaddr*)&remote_addr, sizeof(remote_addr));
        printf("Send Message%s,%d\n", buf,i);
    }
    closesocket(socked);
    return 0;
}