first version

src/network/multicastsocket.c

@@ -0,0 +1,83 @@
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+
+#include "multicastsocket.h"
+
+// based on: http://openbook.rheinwerk-verlag.de/linux_unix_programmierung/Kap11-018.htm
+
+static struct ip_mreq command;
+
+int setup_multicast_socket(const char *_multicast_ip, unsigned short _multicast_port, struct sockaddr_in *addr) {
+    int loop = 1;
+    int sock;
+
+    memset(addr, 0, sizeof(*addr));
+    addr->sin_family = AF_INET;
+    addr->sin_addr.s_addr = inet_addr(_multicast_ip);
+    addr->sin_port = htons (_multicast_port);
+
+    if ((sock = socket(PF_INET, SOCK_DGRAM, 0)) == -1) {
+        perror("socket()");
+        exit(EXIT_FAILURE);
+    }
+
+    // allow multiple processes to use the same port
+    loop = 1;
+    if (setsockopt(sock,
+                   SOL_SOCKET,
+                   SO_REUSEADDR,
+                   &loop, sizeof(loop)) < 0) {
+        perror("setsockopt:SO_REUSEADDR");
+        exit(EXIT_FAILURE);
+    }
+    if (bind(sock,
+             (struct sockaddr *) addr,
+             sizeof(*addr)) < 0) {
+        perror("bind");
+        exit(EXIT_FAILURE);
+    }
+
+    // allow broadcast
+    loop = 1;
+    if (setsockopt(sock,
+                   IPPROTO_IP,
+                   IP_MULTICAST_LOOP,
+                   &loop, sizeof(loop)) < 0) {
+        perror("setsockopt:IP_MULTICAST_LOOP");
+        exit(EXIT_FAILURE);
+    }
+
+    // join broadcast group
+    command.imr_multiaddr.s_addr = inet_addr(_multicast_ip);
+    command.imr_interface.s_addr = htonl (INADDR_ANY);
+    if (command.imr_multiaddr.s_addr == -1) {
+        perror("Wrong multicast address!\n");
+        exit(EXIT_FAILURE);
+    }
+    if (setsockopt(sock,
+                   IPPROTO_IP,
+                   IP_ADD_MEMBERSHIP,
+                   &command, sizeof(command)) < 0) {
+        perror("setsockopt:IP_ADD_MEMBERSHIP");
+    }
+    return sock;
+}
+
+int remove_multicast_socket(int socket) {
+    if (setsockopt(socket,
+                   IPPROTO_IP,
+                   IP_DROP_MEMBERSHIP,
+                   &command, sizeof(command)) < 0) {
+        perror("setsockopt:IP_DROP_MEMBERSHIP");
+        return -1;
+    }
+    return 0;
+}