hi,
there're some os wher this is not required for receiving multicast packet.
man 7 ip
IP_ADD_MEMBERSHIP
Join a multicast group. Argument is a struct ip_mreqn structure.
struct ip_mreqn
{
struct in_addr imr_multiaddr; /* IP multicast group address */
struct in_addr imr_address; /* IP address of local interface */
int imr_ifindex; /* interface index */
};
imr_multiaddr contains the address of the multicast group the application
wants to join or leave. It must be a valid multicast
address. imr_address is the address of the local interface with which the
system should join the multicast group; if it is equal
to INADDR_ANY an appropriate interface is chosen by the system. imr_ifindex
is the interface index of the interface that
should join/leave the imr_multiaddr group, or 0 to indicate any interface.
For compatibility, the old ip_mreq structure is still supported. It differs
from ip_mreqn only by not including the
imr_ifindex field. Only valid as a setsockopt(2).
Calvin Austin wrote:
>
> I don't know if anyone else can verify this, but the bug listed below
> seems to be BSD socket related (ie OS related)
>
> I hacked some code together from an online example and included what
> Java does on the server side , compile cc -o serv serv.c and
> test with the Broadcaster client from the bug report.
>
> If the ip address field is not used then the server gets the broadcast
> packets
> (it works) If the address is used then it doesn't. I'm thinking that
> this
> may be trapped elsewhere and not in Java
>
> regards
> calvin
>
> Jason Gilbert wrote:
> >
>
> > 3) Bug 4191980
> > (http://developer.java.sun.com/developer/bugParade/bugs/4191980.html).
> > It's amazing that this has been around since 1.1.6 (probably
> > earlier). Sadly, if
> > the jdk was in fact Free Software this would have easily been
> > fixed. Don't mention
> > the Sun open source license (I don't remember what it's called
> > today). That's more
> > of a lock-in than Microsoft. At least they just lock you into
> > using there software
> > by not being compatible with other software. Sun wants people
> > to effectively lock
> > themselves into using only the Sun implementation. There
> > attempt at blocking
> > 'forking' basically would appear to block creating or working
> > on another implementation.
> > Kaffe for instance. Or blocking real innovation by allowing
> > someone to say, "hey,
> > these people are completely off base with their impl, I could
> > make the JVM 100x faster
> > by doing X" and then release it under the GPL. they're
> > already tainted. I think the
> > shortcoming is basically that Sun is trying to create this
> > "community" which seems to
> > be on only a product by product basis when the real community
> > already exists which is
> > the software developer community. small pond, largest pond.
> >
>
> > jason
> >
> > --
> > Jason Gilbert | http://home.hiwaay.net/~gilbertj/
> > ------------------------------------------------------
> > I wish I could make the garbage collector thread in my
> > brain less aggressive.
> >
> > ----------------------------------------------------------------------
> > To UNSUBSCRIBE, email to [EMAIL PROTECTED]
> > with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
>
> --------------------------------------------------------------------------------
> #include <stdio.h>
> #include <string.h>
> #include <errno.h>
> #include <sys/socket.h>
>
> #include <netinet/in.h>
> #include <arpa/inet.h>
>
> typedef int SIZE_T;
> #define PACKET_SIZE 1024
>
>
> main(int argc, char **argv)
> {
> int rr;
> int rc;
> int sockfd;
> SIZE_T client_addr_len;
> char *cmd_name;
> char send_data[PACKET_SIZE];
> char recv_data[PACKET_SIZE];
> struct sockaddr_in servaddr;
> struct sockaddr client_addr;
>
> cmd_name = argv[0];
>
> /*
> * Create a socket.
> */
> sockfd = socket(AF_INET, SOCK_DGRAM, 0);
> if (sockfd < 0) {
> printf("%s: socket errno = %d\n", cmd_name, errno);
>exit(-1);
> }
>
> /*
> * Initialize the address the socket will bind to.
> */
> bzero(&servaddr, sizeof(servaddr));
> servaddr.sin_family = AF_INET;
> servaddr.sin_port = htons(3000);
> /*
> * NOTE: assigning INADDR_ANY works
> but listening to the machines own address does not receive broadcast
> udp for that subnet */
> servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
> /*servaddr.sin_addr.s_addr = htonl(0x81907D7C);*/
> /*servaddr.sin_addr.s_addr = htonl(0x81907D6F);*/
>
> /*
> * Bind the socket to the address.
> */
> rc = bind(sockfd, (struct sockaddr *) &servaddr,
> sizeof(servaddr));
> if (rc < 0) {
> printf("%s: bind errno = %d\n", cmd_name, errno);
>exit(-1);
> }
>
> /*
> * In each loop iteration, we wait for a packet from the * client.
>When a packet arrives, we echo its contents
> * and send a response back to the client of the form
> * "response #rr".
> */
> for (rr = 1; ; rr++) {
> client_addr_len = sizeof(client_addr);
> printf("%s: about to receive packet\n", cmd_name);
>fflush(stdout);
> /*
> * Wait for a packet from the client.
> */
> rc = recvfrom(sockfd, recv_data, PACKET_SIZE, 0,
> &client_addr, &client_addr_len); if (rc
> < 0) {
> printf("%s: recvfrom failed: errno = %d\n",
> cmd_name, errno);
> } else {
> printf("%s: recvfrom received packet #%d: %s\n",
> cmd_name, rr, recv_data);
> }
> }
> }
--
-- Levente
"The only thing worse than not knowing the truth is
ruining the bliss of ignorance."
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