UDP广播，组播服务器

广播

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <net/if.h>
#define SERVER_PORT 8000
#define CLIENT_PORT 9000
#define MAXLINE 1500
#define BROADCAST_IP "192.168.32.255"

int main(void)
{
    int sockfd;
    struct sockaddr_in serveraddr, clientaddr;
    char buf[MAXLINE] = "xingwenpeng
";

    /* 构造用于UDP通信的套接字 */
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);

    bzero(&serveraddr, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;            /* IPv4 */
    serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);         /* 本地任意IP INADDR_ANY = 0 */
    serveraddr.sin_port = htons(SERVER_PORT);

    bind(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr));

    int flag = 1;
    setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &flag, sizeof(flag));


    /*构造 client 地址 IP+端口  192.168.32.255+9000 */
    bzero(&clientaddr, sizeof(clientaddr));
    clientaddr.sin_family = AF_INET;
    inet_pton(AF_INET, BROADCAST_IP, &clientaddr.sin_addr.s_addr);
    clientaddr.sin_port = htons(CLIENT_PORT);

    int i = 0;
    while (1) {
        sprintf(buf, "itcast %d
", i++);
        //fgets(buf, sizeof(buf), stdin);
        sendto(sockfd, buf, strlen(buf), 0, (struct sockaddr *)&clientaddr, sizeof(clientaddr));
        sleep(1);
    }
    close(sockfd);
    return 0;
}

client

#include <netinet/in.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <net/if.h>
#define SERVER_PORT 8000
#define MAXLINE 4096

#define CLIENT_PORT 9000
int main(int argc, char *argv[])
{
    struct sockaddr_in serveraddr, localaddr;
    int confd;
    ssize_t len;
    char buf[MAXLINE];

    //1.创建一个socket
    confd = socket(AF_INET, SOCK_DGRAM, 0);

    //2.初始化本地端地址
    bzero(&localaddr, sizeof(localaddr));
    localaddr.sin_family = AF_INET;
    inet_pton(AF_INET, "0.0.0.0" , &localaddr.sin_addr.s_addr);
    localaddr.sin_port = htons(CLIENT_PORT);

    bind(confd, (struct sockaddr *)&localaddr, sizeof(localaddr));

    socklen_t slen;
    while (1) {
        slen = sizeof(serveraddr);
        len = recvfrom(confd, buf, sizeof(buf), 0, (struct sockaddr *)&serveraddr, &slen);
        printf("%s", buf);
        //printf("%s
", inet_ntop(AF_INET, &serveraddr.sin_addr.s_addr, buf, sizeof(buf)));
        //write(STDOUT_FILENO, buf, len);
    }
    close(confd);
    return 0;
}

组播

组播组可以是永久的也可以是临时的。组播组地址中，有一部分由官方分配的，称为永久组播组。永久组播组保持不变的是它的ip地址，组中的成员构成可以发生变化。

永久组播组中成员的数量都可以是任意的，甚至可以为零。那些没有保留下来供永久组播组使用的ip组播地址，可以被临时组播组利用。

224.0.0.0～224.0.0.255为预留的组播地址（永久组地址），地址224.0.0.0保留不做分配，其它地址供路由协议
使用；
224.0.1.0～224.0.1.255是公用组播地址，可以用于Internet；
224.0.2.0～238.255.255.255为用户可用的组播地址（临时组地址），全网范围内有效；
239.0.0.0～239.255.255.255为本地管理组播地址，仅在特定的本地范围内有效。
ip ad
查看网卡编号
if_nametoindex 

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <net/if.h>
#define SERVER_PORT 8000
#define CLIENT_PORT 9000
#define MAXLINE 1500

#define GROUP "239.0.0.2"

int main(void)
{
    int sockfd;
    struct sockaddr_in serveraddr, clientaddr;
    char buf[MAXLINE] = "xingwenpeng
";
    struct ip_mreqn group;

    /* 构造用于UDP通信的套接字 */
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);

    bzero(&serveraddr, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;            /* IPv4 */
    serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);         /* 本地任意IP INADDR_ANY = 0 */
    serveraddr.sin_port = htons(SERVER_PORT);
    bind(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr));

    /*设置组地址*/
    inet_pton(AF_INET, GROUP, &group.imr_multiaddr);
    /*本地任意IP*/
    inet_pton(AF_INET, "0.0.0.0", &group.imr_address);
    /* eth0 --> 编号
     * 命令:ip ad */
    group.imr_ifindex = if_nametoindex("eth0");

    setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_IF, &group, sizeof(group));

    /*构造 client 地址 IP+端口 */
    bzero(&clientaddr, sizeof(clientaddr));
    clientaddr.sin_family = AF_INET;
    /* IPv4  239.0.0.2+9000 */
    inet_pton(AF_INET, GROUP, &clientaddr.sin_addr.s_addr);
    clientaddr.sin_port = htons(CLIENT_PORT);

    int i = 0;
    while (1) {
        sprintf(buf, "itcast %d
", i++);
        //fgets(buf, sizeof(buf), stdin);
        sendto(sockfd, buf, strlen(buf), 0, (struct sockaddr *)&clientaddr, sizeof(clientaddr));
        sleep(1);
    }
    close(sockfd);
    return 0;
}

client

#include <netinet/in.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <net/if.h>
#define SERVER_PORT 8000
#define MAXLINE 4096

#define CLIENT_PORT 9000
#define GROUP "239.0.0.2"
int main(int argc, char *argv[])
{
    struct sockaddr_in serveraddr, localaddr;
    int confd;
    ssize_t len;
    char buf[MAXLINE];
    /* 组播结构体 */
    struct ip_mreqn group;
    //1.创建一个socket
    confd = socket(AF_INET, SOCK_DGRAM, 0);

    //2.初始化本地端地址
    bzero(&localaddr, sizeof(localaddr));
    localaddr.sin_family = AF_INET;
    inet_pton(AF_INET, "0.0.0.0" , &localaddr.sin_addr.s_addr);
    localaddr.sin_port = htons(CLIENT_PORT);
    bind(confd, (struct sockaddr *)&localaddr, sizeof(localaddr));

    /*设置组地址*/
    inet_pton(AF_INET, GROUP, &group.imr_multiaddr);
    /*本地任意IP*/
    inet_pton(AF_INET, "0.0.0.0", &group.imr_address);
    /* eth0 --> 编号
    //命令:ip ad */
    group.imr_ifindex = if_nametoindex("eth0");
    /*设置client 加入多播组 */
    setsockopt(confd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &group, sizeof(group));

    while (1) {
        len = recvfrom(confd, buf, sizeof(buf), 0, NULL, 0);
        write(STDOUT_FILENO, buf, len);
    }
    close(confd);
    return 0;
}