MulticastAddress.java

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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */


import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.UnknownHostException;
import java.net.SocketException;

/**
 * Parses and represents a multicast address.
 */

class MulticastAddress {
    private final InetAddress group;
    private final int port;
    private final NetworkInterface interf;

    private MulticastAddress(InetAddress group, int port, NetworkInterface interf) {
        this.group = group;
        this.port = port;
        this.interf = interf;
    }

    InetAddress group() {
        return group;
    }

    int port() {
        return port;
    }

    /**
     * @return  The network interface, may be {@code null}
     */
    NetworkInterface interf() {
        return interf;
    }

    /**
     * Parses a string of the form "group:port[@interface]", returning
     * a MulticastAddress representing the address
     */
    static MulticastAddress parse(String s) {
        String[] components = s.split("@");
        if (components.length > 2)
            throw new IllegalArgumentException("At most one '@' expected");

        // get group and port
        String target = components[0];
        int len = components[0].length();
        int colon = components[0].lastIndexOf(':');
        if ((colon < 1) || (colon > (len-2)))
            throw new IllegalArgumentException("group:port expected");
        String groupString = target.substring(0, colon);
        int port = -1;
        try {
            port = Integer.parseInt(target.substring(colon+1, len));
        } catch (NumberFormatException x) {
             throw new IllegalArgumentException(x);
        }

        // handle IPv6 literal address
        if (groupString.charAt(0) == '[') {
            len = groupString.length();
            if (groupString.charAt(len-1) != ']')
                throw new IllegalArgumentException("missing ']'");
            groupString = groupString.substring(1,len-1);
            if (groupString.length() == 0)
                throw new IllegalArgumentException("missing IPv6 address");
        }

        // get group address
        InetAddress group = null;
        try {
            group = InetAddress.getByName(groupString);
        } catch (UnknownHostException x) {
            throw new IllegalArgumentException(x);
        }
        if (!group.isMulticastAddress()) {
            throw new IllegalArgumentException("'" + group.getHostAddress() +
                "' is not multicast address");
        }

        // optional interface
        NetworkInterface interf = null;
        if (components.length == 2) {
            try {
                interf = NetworkInterface.getByName(components[1]);
            } catch (SocketException x) {
                throw new IllegalArgumentException(x);
            }
            if (interf == null) {
                throw new IllegalArgumentException("'" + components[1] +
                   "' is not valid interface");
            }
        }
        return new MulticastAddress(group, port, interf);
    }
}