Multicast (multicast) implemented under Linux

Unicast can only be sent to one receiver, but when sent to multiple receivers, it is not only consuming traffic, but also time consuming, total traffic = The receiver of the traffic per recipient.

Broadcast mode is sent to all hosts, the disadvantage of broadcasting is to cause information pollution, a large amount of information will occupy the network bandwidth.

Multicast (multicast): Only hosts that join a multicast group can receive data. Multicasting can be sent to multiple hosts and avoids excessive loads like broadcasts.

Multicast address is Class D address: 224.0.1.1-239.255.255.255

Then the code is implemented as follows:

Group Advertisement Send

1#include <sys/socket.h>2#include <sys/types.h>3#include <arpa/inet.h>4#include <netinet/inch.h>5#include <stdio.h>6#include <stdlib.h>7#include <errno.h>8#include <error.h>9#include <string.h>Ten#include <unistd.h> One#include <time.h> A  - #defineMcast_port 50001 - #defineMcast_addr "239.0.0.1" the  - #defineError_exit (_errmsg_) error (Exit_failure, errno, _errmsg_) -  - #defineBuff_size 1024 +  - intMain () + { A     intsockfd; at     structsockaddr_in mcastaddr; -     Char*buff =NULL; -     intnbytes; - time_t time_sec; -      -     /** Create user packet sockets **/ in     if(-1= = (SOCKFD = socket (af_inet, SOCK_DGRAM,0)))  -Error_exit ("Socket"); to          +     /** Specify the recipient address as the multicast address **/ -mcastaddr.sin_family =af_inet; theMcastaddr.sin_port =htons (mcast_port); *MCASTADDR.SIN_ADDR.S_ADDR =inet_addr (mcast_addr); $     Panax Notoginseng     /** Connect to the multicast address **/ -     if(-1= = Connect (SOCKFD, (structSOCKADDR *) &mcastaddr,sizeof(MCASTADDR))) theError_exit ("Bind"); +  ATime (&time_sec); the      while(2)  { +Sleep1); -Time_sec + +; $Buff = CTime (&time_sec); $printf"%s", buff); -         /** Data transmission **/ -         if(-1= = Send (SOCKFD, buff, strlen (buff),0)) theError_exit ("Send"); -     }Wuyi Close (SOCKFD); the  -     return 0; Wu}

Multicast receive, with multiple receivers

1#include <stdio.h>2#include <stdlib.h>3#include <errno.h>4#include <sys/types.h>5#include <sys/socket.h>6#include <netinet/inch.h>7#include <arpa/inet.h>8#include <unistd.h>9#include <string.h>Ten#include <strings.h> One  A #defineN 128 -  -typedefstructsockaddr SA; the  - intMainintargcConst Char*argv[]) - { -     intsockfd; +      -     /** Create user packet sockets **/ +     if(SOCKFD = socket (af_inet, SOCK_DGRAM,0)) == -1) A     { atPerror ("Socket"); -Exit (-1); -     } -          -     structsockaddr_in myaddr; -myaddr.sin_family =af_inet; inMYADDR.SIN_ADDR.S_ADDR = inet_addr ("239.0.0.1"); -Myaddr.sin_port = htons (50001); to      +     /** Bind multicast ip**/ -     if(Bind (SOCKFD, (structSOCKADDR *) &myaddr,sizeof(MYADDR)) == -1) the     { *Perror ("Bind"); $Exit (-1);Panax Notoginseng     } -      the     /* + * * struct Ip_mreq { A * * struct in_addr imr_multiaddr; IP Multicast address of group set up multicast group addresses the * * struct in_addr imr_interface; Local IP address of interface native IP +     ** }; -     */ $     /** Join a multicast group **/ $     structip_mreq mreq; -Bzero (&mreq,sizeof(Mreq)); -MREQ.IMR_MULTIADDR.S_ADDR = inet_addr ("239.0.0.1"); theMREQ.IMR_INTERFACE.S_ADDR = inet_addr (/*"0.0.0.0"*/"192.168.1.24"); -         Wuyi     if(SetSockOpt (SOCKFD, Ipproto_ip, Ip_add_membership, &mreq,sizeof(Mreq)) <0) the     { -Perror ("setsockopt"); WuExit (-1); -     } About  $     CharBuf[n] = {0}; -  -      while(1) -     { A         /** Waiting to receive data **/ +Recvfrom (SOCKFD, buf, N,0, NULL, NULL); theprintf"recv:%s\n", buf); -     } $  the Close (SOCKFD); the     return 0; the}

Multicast (multicast) implemented under Linux