Getting `Can't assign requested address` java.net.SocketException using Ehcache multicast

Question

Getting java.net.SocketException when trying to start a multicast provider:

2013-09-11 11:45:44,204 [main] ERROR net.sf.ehcache.distribution.Mul         


        

Answer 1

You need to add certain configurations to Java VM before you can join a Multicast socket in any machine.

First add this line before attempting any connection to make sure you will get only IPv4 addresses:

System.setProperty("java.net.preferIPv4Stack", "true");

In most of the cases your computer has more than one network interface, so you need to choose the correct one:

Enumeration networkInterfaces = NetworkInterface.getNetworkInterfaces();
while (networkInterfaces.hasMoreElements()) {
    NetworkInterface networkInterface = networkInterfaces.nextElement();
    Enumeration addressesFromNetworkInterface = networkInterface.getInetAddresses();
    while (addressesFromNetworkInterface.hasMoreElements()) {
        InetAddress inetAddress = addressesFromNetworkInterface.nextElement();
        if (inetAddress.isSiteLocalAddress()
                && !inetAddress.isAnyLocalAddress()
                && !inetAddress.isLinkLocalAddress()
                && !inetAddress.isLoopbackAddress()
                && !inetAddress.isMulticastAddress()) {
            socket.setNetworkInterface(NetworkInterface.getByName(networkInterface.getName()));
        }
    }
}