Default to IPv4 if IPv6 not supported

src/main.cpp

@@ -939,6 +939,11 @@ int main(int argc, char *argv[])
                 audio_host = requested_receiver;
         }
 
+        if (!is_ipv6_supported()) {
+                log_msg(LOG_LEVEL_WARNING, "IPv6 support missing, setting IPv4-only mode.\n");
+                force_ip_version = 4;
+        }
+
         if (!set_output_buffering()) {
                 log_msg(LOG_LEVEL_WARNING, "Cannot set console output buffering!\n");
         }

src/utils/net.c

@@ -297,3 +297,13 @@ bool get_local_addresses(struct sockaddr_storage *addrs, size_t *len, int ip_ver
 #endif
 }
 
+bool is_ipv6_supported(void)
+{
+        int fd = socket(AF_INET6, SOCK_DGRAM, 0);
+        if (fd == INVALID_SOCKET && errno == EAFNOSUPPORT) {
+                return false;
+        }
+        CLOSESOCKET(fd);
+        return true;
+}
+

src/utils/net.h

@@ -48,6 +48,7 @@ bool is_addr_loopback(struct sockaddr *sa);
 bool is_host_loopback(const char *hostname);
 uint16_t socket_get_recv_port(int fd);
 bool get_local_addresses(struct sockaddr_storage *addrs, size_t *len, int ip_version);
+bool is_ipv6_supported(void);
 
 #ifdef WIN32
 #define CLOSESOCKET closesocket