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Wie konfiguriere ich Multicast?

Kann jemand bitte die Schritte erklären, die zum Konfigurieren eines Multicasts in Ubuntu erforderlich sind? Ich habe ein einfaches Programm aus dem Internet. Beim Ausführen des Client-Programms treten Fehler auf. Ich erhalte den Fehler als:

Opening datagram socket....OK.  
Setting SO_REUSEADDR...OK.  
Binding datagram socket...OK.  
Adding multicast group error: No such device: 

Wenn ich das Serverprogramm ausführe, erhalte ich den Fehler als:

Opening the datagram socket...OK.
Setting local interface error: Cannot assign requested address

Ich benutze Ubuntu, um das Programm auszuführen. Ich habe zwei verschiedene Laptops, die jedoch über dasselbe Netzwerk verbunden sind. Ich verwende ein drahtloses Netzwerk, um den obigen Vorgang auszuführen.

Client-Programm

#include <sys/types.h>  
#include <sys/socket.h>  
#include <arpa/inet.h>  
#include <netinet/in.h>  
#include <stdio.h>  
#include <stdlib.h>  


struct sockaddr_in localSock;
struct ip_mreq group;
int sd;
int datalen;
char databuf[1024];

int main(int argc, char *argv[])
{
/* Create a datagram socket on which to receive. */
sd = socket(AF_INET, SOCK_DGRAM, 0);
if(sd < 0)
{
perror("Opening datagram socket error");
exit(1);
}
else
printf("Opening datagram socket....OK.\n");

/* Enable SO_REUSEADDR to allow multiple instances of this */
/* application to receive copies of the multicast datagrams. */
{
int reuse = 1;
if(setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, (char *)&reuse, sizeof(reuse)) < 0)
{
perror("Setting SO_REUSEADDR error");
close(sd);
exit(1);
}
else
printf("Setting SO_REUSEADDR...OK.\n");
}

/* Bind to the proper port number with the IP address */
/* specified as INADDR_ANY. */
memset((char *) &localSock, 0, sizeof(localSock));
localSock.sin_family = AF_INET;
localSock.sin_port = htons(4321);
localSock.sin_addr.s_addr = INADDR_ANY;
if(bind(sd, (struct sockaddr*)&localSock, sizeof(localSock)))
{
perror("Binding datagram socket error");
close(sd);
exit(1);
}
else
printf("Binding datagram socket...OK.\n");

/* Join the multicast group 226.1.1.1 on the local 203.106.93.94 */
/* interface. Note that this IP_ADD_MEMBERSHIP option must be */
/* called for each local interface over which the multicast */
/* datagrams are to be received. */
group.imr_multiaddr.s_addr = inet_addr("224.0.0.0");
group.imr_interface.s_addr = inet_addr("233.106.93.94");
if(setsockopt(sd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *)&group, sizeof(group)) < 0)
{
perror("Adding multicast group error");
close(sd);
exit(1);
}
else
printf("Adding multicast group...OK.\n");

/* Read from the socket. */
datalen = sizeof(databuf);
if(read(sd, databuf, datalen) < 0)
{
perror("Reading datagram message error");
close(sd);
exit(1);
}
else
{
printf("Reading datagram message...OK.\n");
printf("The message from multicast server is: \"%s\"\n", databuf);
}
return 0;
}

Server-Programm

#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
struct in_addr localInterface;
struct sockaddr_in groupSock;
int sd;
char databuf[1024] = "Multicast test message lol!";
int datalen = sizeof(databuf);

int main (int argc, char *argv[ ])
{
/* Create a datagram socket on which to send. */
sd = socket(AF_INET, SOCK_DGRAM, 0);
if(sd < 0)
{
  perror("Opening datagram socket error");
  exit(1);
}
else
  printf("Opening the datagram socket...OK.\n");

/* Initialize the group sockaddr structure with a */
/* group address of 225.1.1.1 and port 5555. */
memset((char *) &groupSock, 0, sizeof(groupSock));
groupSock.sin_family = AF_INET;
groupSock.sin_addr.s_addr = inet_addr("224.0.0.0");
groupSock.sin_port = htons(4321);

/* Disable loopback so you do not receive your own datagrams.
{
char loopch = 0;
if(setsockopt(sd, IPPROTO_IP, IP_MULTICAST_LOOP, (char *)&loopch, sizeof(loopch)) < 0)
{
perror("Setting IP_MULTICAST_LOOP error");
close(sd);
exit(1);
}
else
printf("Disabling the loopback...OK.\n");
}
*/

/* Set local interface for outbound multicast datagrams. */
/* The IP address specified must be associated with a local, */
/* multicast capable interface. */
localInterface.s_addr = inet_addr("233.106.93.94");
if(setsockopt(sd, IPPROTO_IP, IP_MULTICAST_IF, (char *)&localInterface, sizeof(localInterface)) < 0)
{
  perror("Setting local interface error");
  exit(1);
}
else
  printf("Setting the local interface...OK\n");
/* Send a message to the multicast group specified by the*/
/* groupSock sockaddr structure. */
/*int datalen = 1024;*/
if(sendto(sd, databuf, datalen, 0, (struct sockaddr*)&groupSock, sizeof(groupSock)) < 0)
{perror("Sending datagram message error");}
else
  printf("Sending datagram message...OK\n");

/* Try the re-read from the socket if the loopback is not disable
if(read(sd, databuf, datalen) < 0)
{
perror("Reading datagram message error\n");
close(sd);
exit(1);
}
else
{
printf("Reading datagram message from client...OK\n");
printf("The message is: %s\n", databuf);
}
*/
return 0;
}
3
iwant2learn

Auf den ersten Blick scheint group.imr_interface.s_addr = inet_addr("233.106.93.94"); eine falsche IP-Adresse zu haben, da die IP-Adresse hinzugefügt werden sollte, die sich auf der Schnittstelle selbst befindet.

Die im Beispiel verwendete IP-Adresse war 203.106.93.94, du solltest das wahrscheinlich durch die IP-Adresse ersetzen, die du auf eth0 oder ähnlichem hast.

2
ajmitch