* 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 1.1 */ public class MulticastSocket extends DatagramSocket { /** * Used on some platforms to record if an outgoing interface * has been set for this socket. */ private boolean interfaceSet; /** * Create a multicast socket. * *
If there is a security manager, * its {@code 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. When * {@link StandardSocketOptions#SO_REUSEPORT SO_REUSEPORT} is * supported then * {@link DatagramSocketImpl#setOption(SocketOption, Object)} * is called to enable the socket option. * * @exception IOException if an I/O exception occurs * while creating the MulticastSocket * @exception SecurityException if a security manager exists and its * {@code checkListen} method doesn't allow the operation. * @see SecurityManager#checkListen * @see java.net.DatagramSocket#setReuseAddress(boolean) * @see java.net.DatagramSocketImpl#setOption(SocketOption, Object) */ 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 {@code checkListen} method is first called * with the {@code 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 * {@code 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 {@code null}, create an unbound socket. * *
If there is a security manager, * its {@code 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 {@code 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 * {@code 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); // Enable SO_REUSEPORT if supported before binding if (supportedOptions().contains(StandardSocketOptions.SO_REUSEPORT)) { this.setOption(StandardSocketOptions.SO_REUSEPORT, true); } if (bindaddr != null) { try { bind(bindaddr); } finally { if (!isBound()) close(); } } } /** * 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 {@code 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 {@code 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 * {@code setInterface} or {@code setNetworkInterface}. * *
If there is a security manager, this method first * calls its {@code checkMulticast} method * with the {@code 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, or the platform does not support * multicasting * @exception SecurityException if a security manager exists and its * {@code 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"); } checkAddress(mcastaddr, "joinGroup"); SecurityManager security = System.getSecurityManager(); if (security != null) { security.checkMulticast(mcastaddr); } if (!mcastaddr.isMulticastAddress()) { throw new SocketException("Not a multicast address"); } /** * required for some platforms where it's not possible to join * a group without setting the interface first. */ NetworkInterface defaultInterface = NetworkInterface.getDefault(); if (!interfaceSet && defaultInterface != null) { setNetworkInterface(defaultInterface); } getImpl().join(mcastaddr); } /** * Leave a multicast group. Its behavior may be affected by * {@code setInterface} or {@code setNetworkInterface}. * *
If there is a security manager, this method first * calls its {@code checkMulticast} method * with the {@code 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 * {@code 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"); } checkAddress(mcastaddr, "leaveGroup"); 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 {@code checkMulticast} method * with the {@code 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, or the platform does not support * multicasting * @exception SecurityException if a security manager exists and its * {@code 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(); checkAddress(((InetSocketAddress)mcastaddr).getAddress(), "joinGroup"); 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 {@code checkMulticast} method
* with the {@code 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
* {@code 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();
checkAddress(((InetSocketAddress)mcastaddr).getAddress(), "leaveGroup");
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");
}
checkAddress(inf, "setInterface");
synchronized (infLock) {
getImpl().setOption(SocketOptions.IP_MULTICAST_IF, inf);
infAddress = inf;
interfaceSet = true;
}
}
/**
* Retrieve the address of the network interface used for
* multicast packets.
*
* @return An {@code 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 Because this option is a hint, applications that want to
* verify what loopback mode is set to should call
* {@link #getLoopbackMode()}
* @param disable {@code 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 {@code setInterface}.
*
* If there is a security manager, this method first performs some
* security checks. First, if {@code p.getAddress().isMulticastAddress()}
* is true, this method calls the
* security manager's {@code checkMulticast} method
* with {@code p.getAddress()} and {@code ttl} as its arguments.
* If the evaluation of that expression is false,
* this method instead calls the security manager's
* {@code checkConnect} method with arguments
* {@code p.getAddress().getHostAddress()} and
* {@code 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
* {@code checkMulticast} or {@code 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");
checkAddress(p.getAddress(), "send");
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
private static Set