UDP组播技术

一、    组播介绍

组播通信区别于单播与广播，有效的解决了单播与广播存在的低效率与高限制问题。信息源只需要发送一次信息，在同一组播组中的每个成员就能接收到该信息。具体理论参照百度百科等相关资料，下面主要通过Linux 进行组播实现。

二、     组播实现

1、向组播组发送消息(Send)

/*************************************************************************

       > FileName: MulticastSend.cpp

       > Author: chinanier

       > Mail: [email protected]

       > CreatedTime: 一 11/24 23:10:54 2014

 ************************************************************************/

 

#include <stdlib.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <time.h>

#include <string.h>

#include <stdio.h>

#include <unistd.h>

 

#define HELLO_PORT 12345

#define HELLO_GROUP "225.0.0.37"

 

int main(int argc,char *argv[])

{

    struct sockaddr_in addr;

    int fd, cnt;

    struct ip_mreq mreq;

    char *message="Hello, World!";

   

    /* create what looks like an ordinary UDPsocket */

    if ((fd=socket(AF_INET,SOCK_DGRAM,0)) <0)

    {

        perror("socket");

        exit(1);

    }

   

    /* set up destination address */

    memset(&addr,0,sizeof(addr));

    addr.sin_family=AF_INET;

   addr.sin_addr.s_addr=inet_addr(HELLO_GROUP);

    addr.sin_port=htons(HELLO_PORT);

   

    /* now just sendto() our destination! */

    while (1)

    {

        if (sendto(fd,message,strlen(message),0, (struct sockaddr *) &addr,sizeof(addr)) <0)

        {

            perror("sendto");

            exit(1);

        }

        sleep(1);

    }

}

 

2、向组播组接收消息(Recv)

/*************************************************************************

       > FileName: Multicastrecv.cpp

       > Author: chinanier

       > Mail: [email protected]

       > CreatedTime: 一 11/24 21:35:08 2014

 ************************************************************************/

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

#include <unistd.h>

#include <time.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <arpa/inet.h>

#include <netinet/in.h>

 

#define HELLO_PORT  12345

#define HELLO_GROUP "225.0.0.37"

#define MSGBUFSIZE 256

int main(int argc,char ** argv)

{

       /* create udp socket */

    struct sockaddr_in net_addr;

    struct ip_mreq merq;

    int nbytes =0;

    int addrlen =0;

    char msgbuf[512];

    int fd =0;

    u_int yes = 1;

    fd = socket(AF_INET,SOCK_DGRAM,0);

    if (fd<=0) {

        printf("socket() ");

        perror("");

        exit(1);

    }

    /* allow multiple sockets to use the samePORT number */

    if(setsockopt(fd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(yes)) <0) {

        perror("Reusing ADDRfailed");

        exit(1);

    }

    /* set up destination address */

    memset(&net_addr,0,sizeof(net_addr));

    net_addr.sin_family      = AF_INET;

    net_addr.sin_addr.s_addr =htonl(INADDR_ANY);

    net_addr.sin_port        = htons(HELLO_PORT);

   

    /* bind to receive address */

    if (bind(fd,(struct sockaddr*)&net_addr,sizeof(net_addr)) < 0) {

        perror("bind()");

        exit(1);

    }

    /* get bind result */

    memset(&net_addr,0,sizeof(net_addr));

    addrlen = sizeof(net_addr);

    if ((getsockname(fd,(struct sockaddr*)&net_addr,(socklen_t*)&addrlen))<0) {

        perror("getsockname()");

        exit(1);

    }

    printf("bind port as%u\r\n",ntohs(net_addr.sin_port));

    /* use setsockopt() to request that thekernel join a multicast group */

    merq.imr_multiaddr.s_addr =inet_addr(HELLO_GROUP);

    merq.imr_interface.s_addr =htonl(INADDR_ANY);

    if(setsockopt(fd,IPPROTO_IP,IP_ADD_MEMBERSHIP,&merq,sizeof(merq)) <0) {

        perror("setsockopt()");

        exit(1);

    }

    /* now just enter a read-print loop */

    while (1) {

        addrlen = sizeof(net_addr);

        if ((nbytes =recvfrom(fd,msgbuf,MSGBUFSIZE,0,(struct sockaddr*)&net_addr,

                              (socklen_t*)&addrlen)) <0) {

            perror("recvfrom()");

            exit(1);

        }

        puts(msgbuf);

    }

    return0;

}

 

 

在Linux下编译执行，可得到结果。