+ * A multicast group is specified by a class D IP address
+ * and by a standard UDP port number. Class D IP addresses
+ * are in the range 224.0.0.0 to 239.255.255.255,
+ * inclusive. The address 224.0.0.0 is reserved and should not be used.
+ *
+ * One would join a multicast group by first creating a MulticastSocket
+ * with the desired port, then invoking the
+ * joinGroup(InetAddress groupAddr)
+ * method:
+ *
+ * // join a Multicast group and send the group salutations
+ * ...
+ * String msg = "Hello";
+ * InetAddress group = InetAddress.getByName("228.5.6.7");
+ * MulticastSocket s = new MulticastSocket(6789);
+ * s.joinGroup(group);
+ * DatagramPacket hi = new DatagramPacket(msg.getBytes(), msg.length(),
+ * group, 6789);
+ * s.send(hi);
+ * // get their responses!
+ * byte[] buf = new byte[1000];
+ * DatagramPacket recv = new DatagramPacket(buf, buf.length);
+ * s.receive(recv);
+ * ...
+ * // OK, I'm done talking - leave the group...
+ * s.leaveGroup(group);
+ *
+ *
+ * When one sends a message to a multicast group, all subscribing
+ * recipients to that host and port receive the message (within the
+ * time-to-live range of the packet, see below). The socket needn't
+ * be a member of the multicast group to send messages to it.
+ * + * When a socket subscribes to a multicast group/port, it receives + * datagrams sent by other hosts to the group/port, as do all other + * members of the group and port. A socket relinquishes membership + * in a group by the leaveGroup(InetAddress addr) method. + * Multiple MulticastSocket's may subscribe to a multicast group + * and port concurrently, and they will all receive group datagrams. + *
+ * Currently applets are not allowed to use multicast sockets. + * + * @author Pavani Diwanji + * @since JDK1.1 + */ +public +class MulticastSocket extends DatagramSocket { + /** + * Create a multicast socket. + * + *
If there is a security manager,
+ * its checkListen method is first called
+ * with 0 as its argument to ensure the operation is allowed.
+ * This could result in a SecurityException.
+ *
+ * When the socket is created the
+ * {@link DatagramSocket#setReuseAddress(boolean)} method is
+ * called to enable the SO_REUSEADDR socket option.
+ *
+ * @exception IOException if an I/O exception occurs
+ * while creating the MulticastSocket
+ * @exception SecurityException if a security manager exists and its
+ * checkListen method doesn't allow the operation.
+ * @see SecurityManager#checkListen
+ * @see java.net.DatagramSocket#setReuseAddress(boolean)
+ */
+ public MulticastSocket() throws IOException {
+ this(new InetSocketAddress(0));
+ }
+
+ /**
+ * Create a multicast socket and bind it to a specific port.
+ *
+ *
If there is a security manager,
+ * its checkListen method is first called
+ * with the port argument
+ * as its argument to ensure the operation is allowed.
+ * This could result in a SecurityException.
+ *
+ * When the socket is created the
+ * {@link DatagramSocket#setReuseAddress(boolean)} method is
+ * called to enable the SO_REUSEADDR socket option.
+ *
+ * @param port port to use
+ * @exception IOException if an I/O exception occurs
+ * while creating the MulticastSocket
+ * @exception SecurityException if a security manager exists and its
+ * checkListen method doesn't allow the operation.
+ * @see SecurityManager#checkListen
+ * @see java.net.DatagramSocket#setReuseAddress(boolean)
+ */
+ public MulticastSocket(int port) throws IOException {
+ this(new InetSocketAddress(port));
+ }
+
+ /**
+ * Create a MulticastSocket bound to the specified socket address.
+ *
+ * Or, if the address is null, create an unbound socket.
+ *
+ *
If there is a security manager,
+ * its checkListen method is first called
+ * with the SocketAddress port as its argument to ensure the operation is allowed.
+ * This could result in a SecurityException.
+ *
+ * When the socket is created the
+ * {@link DatagramSocket#setReuseAddress(boolean)} method is
+ * called to enable the SO_REUSEADDR socket option.
+ *
+ * @param bindaddr Socket address to bind to, or null for
+ * an unbound socket.
+ * @exception IOException if an I/O exception occurs
+ * while creating the MulticastSocket
+ * @exception SecurityException if a security manager exists and its
+ * checkListen method doesn't allow the operation.
+ * @see SecurityManager#checkListen
+ * @see java.net.DatagramSocket#setReuseAddress(boolean)
+ *
+ * @since 1.4
+ */
+ public MulticastSocket(SocketAddress bindaddr) throws IOException {
+ super((SocketAddress) null);
+
+ // Enable SO_REUSEADDR before binding
+ setReuseAddress(true);
+
+ if (bindaddr != null) {
+ bind(bindaddr);
+ }
+ }
+
+ /**
+ * The lock on the socket's TTL. This is for set/getTTL and
+ * send(packet,ttl).
+ */
+ private Object ttlLock = new Object();
+
+ /**
+ * The lock on the socket's interface - used by setInterface
+ * and getInterface
+ */
+ private Object infLock = new Object();
+
+ /**
+ * The "last" interface set by setInterface on this MulticastSocket
+ */
+ private InetAddress infAddress = null;
+
+
+ /**
+ * Set the default time-to-live for multicast packets sent out
+ * on this MulticastSocket in order to control the
+ * scope of the multicasts.
+ *
+ *
The ttl is an unsigned 8-bit quantity, and so must be
+ * in the range 0 <= ttl <= 0xFF .
+ *
+ * @param ttl the time-to-live
+ * @exception IOException if an I/O exception occurs
+ * while setting the default time-to-live value
+ * @deprecated use the setTimeToLive method instead, which uses
+ * int instead of byte as the type for ttl.
+ * @see #getTTL()
+ */
+ @Deprecated
+ public void setTTL(byte ttl) throws IOException {
+ if (isClosed())
+ throw new SocketException("Socket is closed");
+ getImpl().setTTL(ttl);
+ }
+
+ /**
+ * Set the default time-to-live for multicast packets sent out
+ * on this {@code MulticastSocket} in order to control the
+ * scope of the multicasts.
+ *
+ *
The ttl must be in the range {@code 0 <= ttl <=
+ * 255} or an {@code IllegalArgumentException} will be thrown.
+ * Multicast packets sent with a TTL of {@code 0} are not transmitted
+ * on the network but may be delivered locally.
+ *
+ * @param ttl
+ * the time-to-live
+ *
+ * @throws IOException
+ * if an I/O exception occurs while setting the
+ * default time-to-live value
+ *
+ * @see #getTimeToLive()
+ */
+ public void setTimeToLive(int ttl) throws IOException {
+ if (ttl < 0 || ttl > 255) {
+ throw new IllegalArgumentException("ttl out of range");
+ }
+ if (isClosed())
+ throw new SocketException("Socket is closed");
+ getImpl().setTimeToLive(ttl);
+ }
+
+ /**
+ * Get the default time-to-live for multicast packets sent out on
+ * the socket.
+ *
+ * @exception IOException if an I/O exception occurs
+ * while getting the default time-to-live value
+ * @return the default time-to-live value
+ * @deprecated use the getTimeToLive method instead, which returns
+ * an int instead of a byte.
+ * @see #setTTL(byte)
+ */
+ @Deprecated
+ public byte getTTL() throws IOException {
+ if (isClosed())
+ throw new SocketException("Socket is closed");
+ return getImpl().getTTL();
+ }
+
+ /**
+ * Get the default time-to-live for multicast packets sent out on
+ * the socket.
+ * @exception IOException if an I/O exception occurs while
+ * getting the default time-to-live value
+ * @return the default time-to-live value
+ * @see #setTimeToLive(int)
+ */
+ public int getTimeToLive() throws IOException {
+ if (isClosed())
+ throw new SocketException("Socket is closed");
+ return getImpl().getTimeToLive();
+ }
+
+ /**
+ * Joins a multicast group. Its behavior may be affected by
+ * setInterface or setNetworkInterface.
+ *
+ *
If there is a security manager, this method first
+ * calls its checkMulticast method
+ * with the mcastaddr argument
+ * as its argument.
+ *
+ * @param mcastaddr is the multicast address to join
+ *
+ * @exception IOException if there is an error joining
+ * or when the address is not a multicast address.
+ * @exception SecurityException if a security manager exists and its
+ * checkMulticast method doesn't allow the join.
+ *
+ * @see SecurityManager#checkMulticast(InetAddress)
+ */
+ public void joinGroup(InetAddress mcastaddr) throws IOException {
+ if (isClosed()) {
+ throw new SocketException("Socket is closed");
+ }
+
+ SecurityManager security = System.getSecurityManager();
+ if (security != null) {
+ security.checkMulticast(mcastaddr);
+ }
+
+ if (!mcastaddr.isMulticastAddress()) {
+ throw new SocketException("Not a multicast address");
+ }
+
+ getImpl().join(mcastaddr);
+ }
+
+ /**
+ * Leave a multicast group. Its behavior may be affected by
+ * setInterface or setNetworkInterface.
+ *
+ *
If there is a security manager, this method first
+ * calls its checkMulticast method
+ * with the mcastaddr argument
+ * as its argument.
+ *
+ * @param mcastaddr is the multicast address to leave
+ * @exception IOException if there is an error leaving
+ * or when the address is not a multicast address.
+ * @exception SecurityException if a security manager exists and its
+ * checkMulticast method doesn't allow the operation.
+ *
+ * @see SecurityManager#checkMulticast(InetAddress)
+ */
+ public void leaveGroup(InetAddress mcastaddr) throws IOException {
+ if (isClosed()) {
+ throw new SocketException("Socket is closed");
+ }
+
+ SecurityManager security = System.getSecurityManager();
+ if (security != null) {
+ security.checkMulticast(mcastaddr);
+ }
+
+ if (!mcastaddr.isMulticastAddress()) {
+ throw new SocketException("Not a multicast address");
+ }
+
+ getImpl().leave(mcastaddr);
+ }
+
+ /**
+ * Joins the specified multicast group at the specified interface.
+ *
+ *
If there is a security manager, this method first
+ * calls its checkMulticast method
+ * with the mcastaddr argument
+ * as its argument.
+ *
+ * @param mcastaddr is the multicast address to join
+ * @param netIf specifies the local interface to receive multicast
+ * datagram packets, or null to defer to the interface set by
+ * {@link MulticastSocket#setInterface(InetAddress)} or
+ * {@link MulticastSocket#setNetworkInterface(NetworkInterface)}
+ *
+ * @exception IOException if there is an error joining
+ * or when the address is not a multicast address.
+ * @exception SecurityException if a security manager exists and its
+ * checkMulticast method doesn't allow the join.
+ * @throws IllegalArgumentException if mcastaddr is null or is a
+ * SocketAddress subclass not supported by this socket
+ *
+ * @see SecurityManager#checkMulticast(InetAddress)
+ * @since 1.4
+ */
+ public void joinGroup(SocketAddress mcastaddr, NetworkInterface netIf)
+ throws IOException {
+ if (isClosed())
+ throw new SocketException("Socket is closed");
+
+ if (mcastaddr == null || !(mcastaddr instanceof InetSocketAddress))
+ throw new IllegalArgumentException("Unsupported address type");
+
+ if (oldImpl)
+ throw new UnsupportedOperationException();
+
+ SecurityManager security = System.getSecurityManager();
+ if (security != null) {
+ security.checkMulticast(((InetSocketAddress)mcastaddr).getAddress());
+ }
+
+ if (!((InetSocketAddress)mcastaddr).getAddress().isMulticastAddress()) {
+ throw new SocketException("Not a multicast address");
+ }
+
+ getImpl().joinGroup(mcastaddr, netIf);
+ }
+
+ /**
+ * Leave a multicast group on a specified local interface.
+ *
+ *
If there is a security manager, this method first
+ * calls its checkMulticast method
+ * with the mcastaddr argument
+ * as its argument.
+ *
+ * @param mcastaddr is the multicast address to leave
+ * @param netIf specifies the local interface or null to defer
+ * to the interface set by
+ * {@link MulticastSocket#setInterface(InetAddress)} or
+ * {@link MulticastSocket#setNetworkInterface(NetworkInterface)}
+ * @exception IOException if there is an error leaving
+ * or when the address is not a multicast address.
+ * @exception SecurityException if a security manager exists and its
+ * checkMulticast method doesn't allow the operation.
+ * @throws IllegalArgumentException if mcastaddr is null or is a
+ * SocketAddress subclass not supported by this socket
+ *
+ * @see SecurityManager#checkMulticast(InetAddress)
+ * @since 1.4
+ */
+ public void leaveGroup(SocketAddress mcastaddr, NetworkInterface netIf)
+ throws IOException {
+ if (isClosed())
+ throw new SocketException("Socket is closed");
+
+ if (mcastaddr == null || !(mcastaddr instanceof InetSocketAddress))
+ throw new IllegalArgumentException("Unsupported address type");
+
+ if (oldImpl)
+ throw new UnsupportedOperationException();
+
+ SecurityManager security = System.getSecurityManager();
+ if (security != null) {
+ security.checkMulticast(((InetSocketAddress)mcastaddr).getAddress());
+ }
+
+ if (!((InetSocketAddress)mcastaddr).getAddress().isMulticastAddress()) {
+ throw new SocketException("Not a multicast address");
+ }
+
+ getImpl().leaveGroup(mcastaddr, netIf);
+ }
+
+ /**
+ * Set the multicast network interface used by methods
+ * whose behavior would be affected by the value of the
+ * network interface. Useful for multihomed hosts.
+ * @param inf the InetAddress
+ * @exception SocketException if there is an error in
+ * the underlying protocol, such as a TCP error.
+ * @see #getInterface()
+ */
+ public void setInterface(InetAddress inf) throws SocketException {
+ if (isClosed()) {
+ throw new SocketException("Socket is closed");
+ }
+ synchronized (infLock) {
+ getImpl().setOption(SocketOptions.IP_MULTICAST_IF, inf);
+ infAddress = inf;
+ }
+ }
+
+ /**
+ * Retrieve the address of the network interface used for
+ * multicast packets.
+ *
+ * @return An InetAddress representing
+ * the address of the network interface used for
+ * multicast packets.
+ *
+ * @exception SocketException if there is an error in
+ * the underlying protocol, such as a TCP error.
+ *
+ * @see #setInterface(java.net.InetAddress)
+ */
+ public InetAddress getInterface() throws SocketException {
+ if (isClosed()) {
+ throw new SocketException("Socket is closed");
+ }
+ synchronized (infLock) {
+ InetAddress ia =
+ (InetAddress)getImpl().getOption(SocketOptions.IP_MULTICAST_IF);
+
+ /**
+ * No previous setInterface or interface can be
+ * set using setNetworkInterface
+ */
+ if (infAddress == null) {
+ return ia;
+ }
+
+ /**
+ * Same interface set with setInterface?
+ */
+ if (ia.equals(infAddress)) {
+ return ia;
+ }
+
+ /**
+ * Different InetAddress from what we set with setInterface
+ * so enumerate the current interface to see if the
+ * address set by setInterface is bound to this interface.
+ */
+ try {
+ NetworkInterface ni = NetworkInterface.getByInetAddress(ia);
+ Enumeration addrs = ni.getInetAddresses();
+ while (addrs.hasMoreElements()) {
+ InetAddress addr = (InetAddress)(addrs.nextElement());
+ if (addr.equals(infAddress)) {
+ return infAddress;
+ }
+ }
+
+ /**
+ * No match so reset infAddress to indicate that the
+ * interface has changed via means
+ */
+ infAddress = null;
+ return ia;
+ } catch (Exception e) {
+ return ia;
+ }
+ }
+ }
+
+ /**
+ * Specify the network interface for outgoing multicast datagrams
+ * sent on this socket.
+ *
+ * @param netIf the interface
+ * @exception SocketException if there is an error in
+ * the underlying protocol, such as a TCP error.
+ * @see #getNetworkInterface()
+ * @since 1.4
+ */
+ public void setNetworkInterface(NetworkInterface netIf)
+ throws SocketException {
+
+ synchronized (infLock) {
+ getImpl().setOption(SocketOptions.IP_MULTICAST_IF2, netIf);
+ infAddress = null;
+ }
+ }
+
+ /**
+ * Get the multicast network interface set.
+ *
+ * @exception SocketException if there is an error in
+ * the underlying protocol, such as a TCP error.
+ * @return the multicast NetworkInterface currently set
+ * @see #setNetworkInterface(NetworkInterface)
+ * @since 1.4
+ */
+ public NetworkInterface getNetworkInterface() throws SocketException {
+ NetworkInterface ni
+ = (NetworkInterface)getImpl().getOption(SocketOptions.IP_MULTICAST_IF2);
+ if (ni.getIndex() == 0) {
+ InetAddress[] addrs = new InetAddress[1];
+ addrs[0] = InetAddress.anyLocalAddress();
+ return new NetworkInterface(addrs[0].getHostName(), 0, addrs);
+ } else {
+ return ni;
+ }
+ }
+
+ /**
+ * Disable/Enable local loopback of multicast datagrams
+ * The option is used by the platform's networking code as a hint
+ * for setting whether multicast data will be looped back to
+ * the local socket.
+ *
+ *
Because this option is a hint, applications that want to
+ * verify what loopback mode is set to should call
+ * {@link #getLoopbackMode()}
+ * @param disable true to disable the LoopbackMode
+ * @throws SocketException if an error occurs while setting the value
+ * @since 1.4
+ * @see #getLoopbackMode
+ */
+ public void setLoopbackMode(boolean disable) throws SocketException {
+ getImpl().setOption(SocketOptions.IP_MULTICAST_LOOP, Boolean.valueOf(disable));
+ }
+
+ /**
+ * Get the setting for local loopback of multicast datagrams.
+ *
+ * @throws SocketException if an error occurs while getting the value
+ * @return true if the LoopbackMode has been disabled
+ * @since 1.4
+ * @see #setLoopbackMode
+ */
+ public boolean getLoopbackMode() throws SocketException {
+ return ((Boolean)getImpl().getOption(SocketOptions.IP_MULTICAST_LOOP)).booleanValue();
+ }
+
+ /**
+ * Sends a datagram packet to the destination, with a TTL (time-
+ * to-live) other than the default for the socket. This method
+ * need only be used in instances where a particular TTL is desired;
+ * otherwise it is preferable to set a TTL once on the socket, and
+ * use that default TTL for all packets. This method does not
+ * alter the default TTL for the socket. Its behavior may be
+ * affected by setInterface.
+ *
+ *
If there is a security manager, this method first performs some
+ * security checks. First, if p.getAddress().isMulticastAddress()
+ * is true, this method calls the
+ * security manager's checkMulticast method
+ * with p.getAddress() and ttl as its arguments.
+ * If the evaluation of that expression is false,
+ * this method instead calls the security manager's
+ * checkConnect method with arguments
+ * p.getAddress().getHostAddress() and
+ * p.getPort(). Each call to a security manager method
+ * could result in a SecurityException if the operation is not allowed.
+ *
+ * @param p is the packet to be sent. The packet should contain
+ * the destination multicast ip address and the data to be sent.
+ * One does not need to be the member of the group to send
+ * packets to a destination multicast address.
+ * @param ttl optional time to live for multicast packet.
+ * default ttl is 1.
+ *
+ * @exception IOException is raised if an error occurs i.e
+ * error while setting ttl.
+ * @exception SecurityException if a security manager exists and its
+ * checkMulticast or checkConnect
+ * method doesn't allow the send.
+ *
+ * @deprecated Use the following code or its equivalent instead:
+ * ......
+ * int ttl = mcastSocket.getTimeToLive();
+ * mcastSocket.setTimeToLive(newttl);
+ * mcastSocket.send(p);
+ * mcastSocket.setTimeToLive(ttl);
+ * ......
+ *
+ * @see DatagramSocket#send
+ * @see DatagramSocket#receive
+ * @see SecurityManager#checkMulticast(java.net.InetAddress, byte)
+ * @see SecurityManager#checkConnect
+ */
+ @Deprecated
+ public void send(DatagramPacket p, byte ttl)
+ throws IOException {
+ if (isClosed())
+ throw new SocketException("Socket is closed");
+ synchronized(ttlLock) {
+ synchronized(p) {
+ if (connectState == ST_NOT_CONNECTED) {
+ // Security manager makes sure that the multicast address
+ // is allowed one and that the ttl used is less
+ // than the allowed maxttl.
+ SecurityManager security = System.getSecurityManager();
+ if (security != null) {
+ if (p.getAddress().isMulticastAddress()) {
+ security.checkMulticast(p.getAddress(), ttl);
+ } else {
+ security.checkConnect(p.getAddress().getHostAddress(),
+ p.getPort());
+ }
+ }
+ } else {
+ // we're connected
+ InetAddress packetAddress = null;
+ packetAddress = p.getAddress();
+ if (packetAddress == null) {
+ p.setAddress(connectedAddress);
+ p.setPort(connectedPort);
+ } else if ((!packetAddress.equals(connectedAddress)) ||
+ p.getPort() != connectedPort) {
+ throw new SecurityException("connected address and packet address" +
+ " differ");
+ }
+ }
+ byte dttl = getTTL();
+ try {
+ if (ttl != dttl) {
+ // set the ttl
+ getImpl().setTTL(ttl);
+ }
+ // call the datagram method to send
+ getImpl().send(p);
+ } finally {
+ // set it back to default
+ if (ttl != dttl) {
+ getImpl().setTTL(dttl);
+ }
+ }
+ } // synch p
+ } //synch ttl
+ } //method
+}