组播通讯实例

sender.c

#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 UDP socket */  
    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);  
    }  
}  

receiver.c

#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"  
#define MSGBUFSIZE 256  
  
int main(int argc, char *argv[])  
{  
    struct sockaddr_in addr;  
    int fd, nbytes,addrlen;  
    struct ip_mreq mreq;  
    char msgbuf[MSGBUFSIZE];  
  
    u_int yes=1; /*** MODIFICATION TO ORIGINAL */  
  
    /* create what looks like an ordinary UDP socket */  
    if ((fd=socket(AF_INET,SOCK_DGRAM,0)) < 0)   
    {  
        perror("socket");  
        exit(1);  
    }  
  
  
    /**** MODIFICATION TO ORIGINAL */  
    /* allow multiple sockets to use the same PORT number */  
    if (setsockopt(fd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(yes)) < 0)   
    {  
        perror("Reusing ADDR failed");  
        exit(1);  
    }  
    /*** END OF MODIFICATION TO ORIGINAL */  
  
    /* set up destination address */  
    memset(&addr,0,sizeof(addr));  
    addr.sin_family=AF_INET;  
    addr.sin_addr.s_addr=htonl(INADDR_ANY); /* N.B.: differs from sender */  
    addr.sin_port=htons(HELLO_PORT);  
  
    /* bind to receive address */  
    if (bind(fd,(struct sockaddr *) &addr,sizeof(addr)) < 0)  
    {  
        perror("bind");  
        exit(1);  
    }  
  
    /* use setsockopt() to request that the kernel join a multicast group */  
    mreq.imr_multiaddr.s_addr=inet_addr(HELLO_GROUP);  
    mreq.imr_interface.s_addr=htonl(INADDR_ANY);  
    if (setsockopt(fd,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq,sizeof(mreq)) < 0)   
    {  
        perror("setsockopt");  
        exit(1);  
    }  
  
    /* now just enter a read-print loop */  
    while (1)   
    {  
        addrlen=sizeof(addr);  
        if ((nbytes=recvfrom(fd,msgbuf,MSGBUFSIZE,0, (struct sockaddr *) &addr,(socklen_t*)&addrlen)) < 0)   
        {  
            perror("recvfrom");  
            exit(1);  
        }  
        puts(msgbuf);  
    }  
  
    return 0;  
}  

Makefile

CC = gcc  
CXX = g++  
CFLAGS = -Wall -D_DEBUG -DDEBUG -g -O0  
LDFLAGS =   
  
MODULE_INC = -I/usr/include  
MODULE_LIB = -L/usr/lib  
  
CFLAGS  += $(MODULE_INC)  
LDFLAGS += $(MODULE_LIB)  
  
  
SENDOBJS = sender.o  
RECVOBJS = receiver.o  
  
  
TARGET = sender receiver  
  
all: $(TARGET)  
  
sender: $(SENDOBJS)  

    $(CXX) -o $@ $^ $(LDFLAGS)  
  
receiver: $(RECVOBJS)  
    
    $(CXX) -o $@ $^ $(LDFLAGS)  
  
clean:   
    rm -f *.o 
    rm -f $(TARGET)  
    rm -f http/*.o  
# make rule  
%.o : %.c  
    $(CC) $(CFLAGS) -c $^ -o $@   
  
%.o : %.cpp  
    $(CC) $(CFLAGS) -c $^ -o $@