UDP组播的c++实现

邗影 / 2023-05-08 / 原文

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;
}

从多播组上拉流，要记得先加入多播组：

// 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(int argc, char* argv[]) {
    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;
    }

    char group[16] = "224.1.2.3";

    struct sockaddr_in local_addr;
    memset(&local_addr, 0, sizeof(local_addr));
    local_addr.sin_family = AF_INET;
    local_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    local_addr.sin_port = htons(20123);

    int ret = bind(socked, (struct sockaddr*)&local_addr, sizeof(local_addr));
    if (ret < 0)
    {
        perror("bind failed !");
        return 3;
    }


    struct ip_mreq mreq;
    inet_pton(AF_INET,group, &mreq.imr_multiaddr.s_addr);
    mreq.imr_interface.s_addr = htonl(INADDR_ANY);

    /*
     *
     *  int setsockopt(int sockfd, int level, int optname,
                      const void *optval, socklen_t optlen);
     * param:
     *      optname
     *          * IP_MULTICAST_LOOP 支持多播数据回送
     *          * IP_ADD_MEMBERSHIP 加入多播组
     *          * IP_DROP_MEMBERSHIP 离开多播组
     *      optval
     *          * IP_MULTICAST_LOOP 选项对应传入 unsigned int 来确认是否支持多播数据回送
     *          * IP_ADD_MEMBERSHIP 传入 ip_mreq
     *          * IP_DROP_MEMBERSHIP 传入 ip_mreq
     *
     * */
    ret = setsockopt(socked, IPPROTO_IP, IP_ADD_MEMBERSHIP, (const char*)&mreq, sizeof(mreq));
    if (ret < 0) {
        perror("setsockopt failed !");
        return 3;
    }
    else
    {
        printf("setsockopt success\n");
    }


    char buf[10240];
    int length = 0;
    struct sockaddr_in sender;
    socklen_t sender_len = sizeof(sender);
    while (true) {
        memset(buf, 0, sizeof(buf));
        length = recvfrom(socked, buf, sizeof(buf), 0, (struct sockaddr*)&sender, &sender_len);
        buf[length] = '\0';
        printf("%s\n", buf);
    }
    setsockopt(socked, IPPROTO_IP, IP_DROP_MEMBERSHIP, (const char*) & mreq, sizeof(mreq));
    closesocket(socked);
    return 0;
}