Socket选项

int getsockopt(int sockfd, int level, int optname,char* optval,int* oplen);
int setsockopt(int sockfd, int level, int optname,char* optval,int* oplen);
/**
sockfd 套接字
level 选项所在协议层
1)SOL_SOCKET:通用套接字选项.
2)IPPROTO_IP:IP选项.
3)IPPROTO_TCP:TCP选项.　
optname 选项名称
optval 选项首地址
optlen 选项值的缓冲区长度
*/

#include <winsock2.h>
#include <windows.h>
#include "stdio.h"
#pragma comment(lib, "ws2_32.lib")
#define PORT 8080

int main()
{

    // 初始化DLL
    WSADATA wsaData;
    WSAStartup(MAKEWORD(2, 2), &wsaData);

    struct sockaddr_in addr;
    char buf[1024];

    // 创建UDP套接字
    SOCKET recvfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (recvfd < 0)
    {
        perror("socket");
        exit(1);
    }

    // 设置接收方地址
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(PORT);
    addr.sin_addr.s_addr = htonl(INADDR_ANY);

    // 绑定套接字
    if (bind(recvfd, (struct sockaddr *)&addr, sizeof(addr)) < 0)
    {
        perror("bind");
        exit(1);
    }

    // 接收消息
    while (1)
    {
        int len = recvfrom(recvfd, buf, sizeof(buf), 0, NULL, 0);
        if (len < 0)
        {
            perror("recvfrom");
            exit(1);
        }
        buf[len] = '\0';
        printf("recv msg from broadcast: %s\n", buf);
    }

    // 关闭套接字
    close(recvfd);
}

typedef struct ip_mreq {
  struct in_addr imr_multiaddr;//加入到的组播地址
  struct in_addr imr_interface;//本机地址
} 
/**
IPv4选项
IP_ADD_MEMBERSHIP 	struct ip_mreq 加入到组播组中 
IP_DROP_MEMBERSHIP 	struct ip_mreq 从组播组中退出 
IP_MULTICAST_IF 	struct ip_mreq 指定提交组播报文的接口 
IP_MULTICAST_TTL 	u_char 指定提交组播报文的TTL 
IP_MULTICAST_LOOP 	u_char 使组播报文环路有效或无效 
*/

#include <winsock2.h>
#include <windows.h>
#include <stdio.h>
#include <ws2tcpip.h>
#include <ws2ipdef.h>
#include <sys/types.h>

#pragma comment(lib, "ws2_32.lib")
#define PORT 1234
#define MULTICAST_GROUP "224.0.0.1"

int main()
{
    // 初始化DLL
    WSADATA wsaData;
    WSAStartup(MAKEWORD(2, 2), &wsaData);

    struct sockaddr_in addr;
    char buf[1024];

    // 创建UDP套接字
    SOCKET sendfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sendfd < 0)
    {
        perror("socket");
        exit(1);
    }

    // 设置组播选项
    int opt = 1;
    setsockopt(sendfd, IPPROTO_IP, IP_MULTICAST_IF, (char *)&opt, sizeof(opt));

    // 设置组播地址
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(PORT);
    inet_pton(AF_INET, MULTICAST_GROUP, &addr.sin_addr);

    // 组播发送消息
    if (sendto(sendfd, buf, strlen(buf), 0, (struct sockaddr *)&addr, sizeof(addr)) < 0)
    {
        perror("sendto");
        exit(1);
    }

    // 关闭套接字
    close(sendfd);

    return 0;
}

#include <winsock2.h>
#include <windows.h>
#include <stdio.h>
#include <ws2tcpip.h>
#pragma comment(lib, "ws2_32.lib")
#define PORT 1234
#define MULTICAST_GROUP "224.0.0.1"

int main()
{
    // 初始化DLL
    WSADATA wsaData;
    WSAStartup(MAKEWORD(2, 2), &wsaData);

    struct sockaddr_in local_addr;
    char buf[1024];

    // 设置要加入组播的地址
    struct ip_mreq mreq;

    // 创建UDP套接字
    SOCKET recvfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (recvfd < 0)
    {
        perror("socket");
        exit(1);
    }

    // 设置组播地址
    memset(&local_addr, 0, sizeof(local_addr));
    local_addr.sin_family = AF_INET;
    local_addr.sin_port = htons(PORT);
    local_addr.sin_addr.s_addr = htonl(INADDR_ANY);

    // 绑定套接字到本地地址
    if (bind(recvfd, (struct sockaddr *)&local_addr, sizeof(local_addr)) < 0)
    {
        perror("bind");
        exit(1);
    }

    // 加入到组播组
    inet_pton(AF_INET, MULTICAST_GROUP, &mreq.imr_multiaddr);
    mreq.imr_interface.s_addr = htonl(INADDR_ANY);
    setsockopt(recvfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *)&mreq, sizeof(mreq));

    // 接收消息
    while (1)
    {
        int len = recvfrom(recvfd, buf, sizeof(buf), 0, NULL, 0);
        if (len < 0)
        {
            perror("recvfrom");
            exit(1);
        }
        buf[len] = '\0';
        printf("recv msg from multicast: %s\n", buf);
    }

    // 退出组播组
    setsockopt(recvfd, IPPROTO_IP, IP_DROP_MEMBERSHIP, (char *)&mreq, sizeof(mreq));

    // 关闭套接字
    close(recvfd);

    return 0;
}