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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package java.nio.channels;

import java.io.IOException;
import java.net.ProtocolFamily;
import java.net.DatagramSocket;
import java.net.SocketOption;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.spi.AbstractSelectableChannel;
import java.nio.channels.spi.SelectorProvider;

A selectable channel for datagram-oriented sockets.
 A datagram channel is created by invoking one of the open methods of this class. It is not possible to create a channel for an arbitrary, pre-existing datagram socket. A newly-created datagram channel is open but not connected. A datagram channel need not be connected in order for the 
send and receive methods to be used. A datagram channel may be connected, by invoking its connect method, in order to avoid the overhead of the security checks are otherwise performed as part of every send and receive operation. A datagram channel must be connected in order to use the read and write methods, since those methods do not accept or return socket addresses. 
 Once connected, a datagram channel remains connected until it is disconnected or closed. Whether or not a datagram channel is connected may be determined by invoking its isConnected method. 
 Socket options are configured using the 
setOption method. A datagram channel to an Internet Protocol socket supports the following options: 


Socket options

  

    
Option Name
    
Description
  


  

    
 SO_SNDBUF 
    
 The size of the socket send buffer 
  
  

    
 SO_RCVBUF 
    
 The size of the socket receive buffer 
  
  

    
 SO_REUSEADDR 
    
 Re-use address 
  
  

    
 SO_BROADCAST 
    
 Allow transmission of broadcast datagrams 
  
  

    
 IP_TOS 
    
 The Type of Service (ToS) octet in the Internet Protocol (IP) header 
  
  

    
 IP_MULTICAST_IF 
    
 The network interface for Internet Protocol (IP) multicast datagrams 
  
  

    
 
      IP_MULTICAST_TTL 
    
 The time-to-live for Internet Protocol (IP) multicast
      datagrams 
  
  

    
 
      IP_MULTICAST_LOOP 
    
 Loopback for Internet Protocol (IP) multicast datagrams 
  



Additional (implementation specific) options may also be supported.
 Datagram channels are safe for use by multiple concurrent threads.  They
support concurrent reading and writing, though at most one thread may be
reading and at most one thread may be writing at any given time.  
Author:
Mark Reinhold, JSR-51 Expert Group
Since:
1.4/**
 * A selectable channel for datagram-oriented sockets.
 *
 * <p> A datagram channel is created by invoking one of the {@link #open open} methods
 * of this class. It is not possible to create a channel for an arbitrary,
 * pre-existing datagram socket. A newly-created datagram channel is open but not
 * connected. A datagram channel need not be connected in order for the {@link #send
 * send} and {@link #receive receive} methods to be used.  A datagram channel may be
 * connected, by invoking its {@link #connect connect} method, in order to
 * avoid the overhead of the security checks are otherwise performed as part of
 * every send and receive operation.  A datagram channel must be connected in
 * order to use the {@link #read(java.nio.ByteBuffer) read} and {@link
 * #write(java.nio.ByteBuffer) write} methods, since those methods do not
 * accept or return socket addresses.
 *
 * <p> Once connected, a datagram channel remains connected until it is
 * disconnected or closed.  Whether or not a datagram channel is connected may
 * be determined by invoking its {@link #isConnected isConnected} method.
 *
 * <p> Socket options are configured using the {@link #setOption(SocketOption,Object)
 * setOption} method. A datagram channel to an Internet Protocol socket supports
 * the following options:
 * <blockquote>
 * <table class="striped">
 * <caption style="display:none">Socket options</caption>
 * <thead>
 *   <tr>
 *     <th scope="col">Option Name</th>
 *     <th scope="col">Description</th>
 *   </tr>
 * </thead>
 * <tbody>
 *   <tr>
 *     <th scope="row"> {@link java.net.StandardSocketOptions#SO_SNDBUF SO_SNDBUF} </th>
 *     <td> The size of the socket send buffer </td>
 *   </tr>
 *   <tr>
 *     <th scope="row"> {@link java.net.StandardSocketOptions#SO_RCVBUF SO_RCVBUF} </th>
 *     <td> The size of the socket receive buffer </td>
 *   </tr>
 *   <tr>
 *     <th scope="row"> {@link java.net.StandardSocketOptions#SO_REUSEADDR SO_REUSEADDR} </th>
 *     <td> Re-use address </td>
 *   </tr>
 *   <tr>
 *     <th scope="row"> {@link java.net.StandardSocketOptions#SO_BROADCAST SO_BROADCAST} </th>
 *     <td> Allow transmission of broadcast datagrams </td>
 *   </tr>
 *   <tr>
 *     <th scope="row"> {@link java.net.StandardSocketOptions#IP_TOS IP_TOS} </th>
 *     <td> The Type of Service (ToS) octet in the Internet Protocol (IP) header </td>
 *   </tr>
 *   <tr>
 *     <th scope="row"> {@link java.net.StandardSocketOptions#IP_MULTICAST_IF IP_MULTICAST_IF} </th>
 *     <td> The network interface for Internet Protocol (IP) multicast datagrams </td>
 *   </tr>
 *   <tr>
 *     <th scope="row"> {@link java.net.StandardSocketOptions#IP_MULTICAST_TTL
 *       IP_MULTICAST_TTL} </th>
 *     <td> The <em>time-to-live</em> for Internet Protocol (IP) multicast
 *       datagrams </td>
 *   </tr>
 *   <tr>
 *     <th scope="row"> {@link java.net.StandardSocketOptions#IP_MULTICAST_LOOP
 *       IP_MULTICAST_LOOP} </th>
 *     <td> Loopback for Internet Protocol (IP) multicast datagrams </td>
 *   </tr>
 * </tbody>
 * </table>
 * </blockquote>
 * Additional (implementation specific) options may also be supported.
 *
 * <p> Datagram channels are safe for use by multiple concurrent threads.  They
 * support concurrent reading and writing, though at most one thread may be
 * reading and at most one thread may be writing at any given time.  </p>
 *
 * @author Mark Reinhold
 * @author JSR-51 Expert Group
 * @since 1.4
 */

public abstract class DatagramChannel
    extends AbstractSelectableChannel
    implements ByteChannel, ScatteringByteChannel, GatheringByteChannel, MulticastChannel
{

    
Initializes a new instance of this class.
Params:
provider – 
        The provider that created this channel/**
     * Initializes a new instance of this class.
     *
     * @param  provider
     *         The provider that created this channel
     */
    protected DatagramChannel(SelectorProvider provider) {
        super(provider);
    }

    
Opens a datagram channel.
 The new channel is created by invoking the 
openDatagramChannel method of the system-wide default SelectorProvider object. The channel will not be connected. 
 The ProtocolFamily of the channel's socket is platform (and possibly configuration) dependent and therefore unspecified. The open allows the protocol family to be selected when opening a datagram channel, and should be used to open datagram channels that are intended for Internet Protocol multicasting. 
Throws:
IOException – 
         If an I/O error occurs
Returns:
 A new datagram channel/**
     * Opens a datagram channel.
     *
     * <p> The new channel is created by invoking the {@link
     * java.nio.channels.spi.SelectorProvider#openDatagramChannel()
     * openDatagramChannel} method of the system-wide default {@link
     * java.nio.channels.spi.SelectorProvider} object.  The channel will not be
     * connected.
     *
     * <p> The {@link ProtocolFamily ProtocolFamily} of the channel's socket
     * is platform (and possibly configuration) dependent and therefore unspecified.
     * The {@link #open(ProtocolFamily) open} allows the protocol family to be
     * selected when opening a datagram channel, and should be used to open
     * datagram channels that are intended for Internet Protocol multicasting.
     *
     * @return  A new datagram channel
     *
     * @throws  IOException
     *          If an I/O error occurs
     */
    public static DatagramChannel open() throws IOException {
        return SelectorProvider.provider().openDatagramChannel();
    }

    
Opens a datagram channel.
 The family parameter is used to specify the ProtocolFamily. If the datagram channel is to be used for IP multicasting then this should correspond to the address type of the multicast groups that this channel will join. 
 The new channel is created by invoking the 
openDatagramChannel method of the system-wide default SelectorProvider object. The channel will not be connected. 
Params:
family – 
         The protocol family
Throws:
UnsupportedOperationException –  If the specified protocol family is not supported. For example, suppose the parameter is specified as StandardProtocolFamily.INET6 but IPv6 is not enabled on the platform.
IOException – 
         If an I/O error occurs
Returns:
 A new datagram channel
Since:
  1.7/**
     * Opens a datagram channel.
     *
     * <p> The {@code family} parameter is used to specify the {@link
     * ProtocolFamily}. If the datagram channel is to be used for IP multicasting
     * then this should correspond to the address type of the multicast groups
     * that this channel will join.
     *
     * <p> The new channel is created by invoking the {@link
     * java.nio.channels.spi.SelectorProvider#openDatagramChannel(ProtocolFamily)
     * openDatagramChannel} method of the system-wide default {@link
     * java.nio.channels.spi.SelectorProvider} object.  The channel will not be
     * connected.
     *
     * @param   family
     *          The protocol family
     *
     * @return  A new datagram channel
     *
     * @throws  UnsupportedOperationException
     *          If the specified protocol family is not supported. For example,
     *          suppose the parameter is specified as {@link
     *          java.net.StandardProtocolFamily#INET6 StandardProtocolFamily.INET6}
     *          but IPv6 is not enabled on the platform.
     * @throws  IOException
     *          If an I/O error occurs
     *
     * @since   1.7
     */
    public static DatagramChannel open(ProtocolFamily family) throws IOException {
        return SelectorProvider.provider().openDatagramChannel(family);
    }

    
Returns an operation set identifying this channel's supported
operations.
 Datagram channels support reading and writing, so this method returns (SelectionKey.OP_READ | SelectionKey.OP_WRITE). 
Returns:
 The valid-operation set/**
     * Returns an operation set identifying this channel's supported
     * operations.
     *
     * <p> Datagram channels support reading and writing, so this method
     * returns {@code (}{@link SelectionKey#OP_READ} {@code |}&nbsp;{@link
     * SelectionKey#OP_WRITE}{@code )}.
     *
     * @return  The valid-operation set
     */
    public final int validOps() {
        return (SelectionKey.OP_READ
                | SelectionKey.OP_WRITE);
    }


    // -- Socket-specific operations --

    
Throws:
AlreadyBoundException –               {@inheritDoc}
UnsupportedAddressTypeException –     {@inheritDoc}
ClosedChannelException –              {@inheritDoc}
IOException –                         {@inheritDoc}
SecurityException –  If a security manager has been installed and its checkListen method denies the operation
Since:
1.7/**
     * @throws  AlreadyBoundException               {@inheritDoc}
     * @throws  UnsupportedAddressTypeException     {@inheritDoc}
     * @throws  ClosedChannelException              {@inheritDoc}
     * @throws  IOException                         {@inheritDoc}
     * @throws  SecurityException
     *          If a security manager has been installed and its {@link
     *          SecurityManager#checkListen checkListen} method denies the
     *          operation
     *
     * @since 1.7
     */
    public abstract DatagramChannel bind(SocketAddress local)
        throws IOException;

    
Throws:
UnsupportedOperationException –           {@inheritDoc}
IllegalArgumentException –                {@inheritDoc}
ClosedChannelException –                  {@inheritDoc}
IOException –                             {@inheritDoc}
Since:
1.7/**
     * @throws  UnsupportedOperationException           {@inheritDoc}
     * @throws  IllegalArgumentException                {@inheritDoc}
     * @throws  ClosedChannelException                  {@inheritDoc}
     * @throws  IOException                             {@inheritDoc}
     *
     * @since 1.7
     */
    public abstract <T> DatagramChannel setOption(SocketOption<T> name, T value)
        throws IOException;

    
Retrieves a datagram socket associated with this channel.
 The returned object will not declare any public methods that are not declared in the DatagramSocket class. 
Returns:
 A datagram socket associated with this channel/**
     * Retrieves a datagram socket associated with this channel.
     *
     * <p> The returned object will not declare any public methods that are not
     * declared in the {@link java.net.DatagramSocket} class.  </p>
     *
     * @return  A datagram socket associated with this channel
     */
    public abstract DatagramSocket socket();

    
Tells whether or not this channel's socket is connected.
Returns:
 true if, and only if, this channel's socket is open and connected/**
     * Tells whether or not this channel's socket is connected.
     *
     * @return  {@code true} if, and only if, this channel's socket
     *          is {@link #isOpen open} and connected
     */
    public abstract boolean isConnected();

    
Connects this channel's socket.
 The channel's socket is configured so that it only receives
datagrams from, and sends datagrams to, the given remote peer
address.  Once connected, datagrams may not be received from or sent to
any other address.  A datagram socket remains connected until it is
explicitly disconnected or until it is closed.
 This method performs exactly the same security checks as the connect method of the DatagramSocket class. That is, if a security manager has been installed then this method verifies that its checkAccept and checkConnect methods permit datagrams to be received from and sent to, respectively, the given remote address. 
 This method may be invoked at any time. It will not have any effect on read or write operations that are already in progress at the moment that it is invoked. If this channel's socket is not bound then this method will first cause the socket to be bound to an address that is assigned automatically, as if invoking the bind method with a parameter of null. 
Params:
remote – 
        The remote address to which this channel is to be connected
Throws:
AlreadyConnectedException – 
         If this channel is already connected
ClosedChannelException – 
         If this channel is closed
AsynchronousCloseException – 
         If another thread closes this channel
         while the connect operation is in progress
ClosedByInterruptException – 
         If another thread interrupts the current thread
         while the connect operation is in progress, thereby
         closing the channel and setting the current thread's
         interrupt status
UnresolvedAddressException – 
         If the given remote address is not fully resolved
UnsupportedAddressTypeException – 
         If the type of the given remote address is not supported
SecurityException – 
         If a security manager has been installed
         and it does not permit access to the given remote address
IOException – 
         If some other I/O error occurs
Returns:
 This datagram channel/**
     * Connects this channel's socket.
     *
     * <p> The channel's socket is configured so that it only receives
     * datagrams from, and sends datagrams to, the given remote <i>peer</i>
     * address.  Once connected, datagrams may not be received from or sent to
     * any other address.  A datagram socket remains connected until it is
     * explicitly disconnected or until it is closed.
     *
     * <p> This method performs exactly the same security checks as the {@link
     * java.net.DatagramSocket#connect connect} method of the {@link
     * java.net.DatagramSocket} class.  That is, if a security manager has been
     * installed then this method verifies that its {@link
     * java.lang.SecurityManager#checkAccept checkAccept} and {@link
     * java.lang.SecurityManager#checkConnect checkConnect} methods permit
     * datagrams to be received from and sent to, respectively, the given
     * remote address.
     *
     * <p> This method may be invoked at any time.  It will not have any effect
     * on read or write operations that are already in progress at the moment
     * that it is invoked. If this channel's socket is not bound then this method
     * will first cause the socket to be bound to an address that is assigned
     * automatically, as if invoking the {@link #bind bind} method with a
     * parameter of {@code null}. </p>
     *
     * @param  remote
     *         The remote address to which this channel is to be connected
     *
     * @return  This datagram channel
     *
     * @throws  AlreadyConnectedException
     *          If this channel is already connected
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  AsynchronousCloseException
     *          If another thread closes this channel
     *          while the connect operation is in progress
     *
     * @throws  ClosedByInterruptException
     *          If another thread interrupts the current thread
     *          while the connect operation is in progress, thereby
     *          closing the channel and setting the current thread's
     *          interrupt status
     *
     * @throws  UnresolvedAddressException
     *          If the given remote address is not fully resolved
     *
     * @throws  UnsupportedAddressTypeException
     *          If the type of the given remote address is not supported
     *
     * @throws  SecurityException
     *          If a security manager has been installed
     *          and it does not permit access to the given remote address
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract DatagramChannel connect(SocketAddress remote)
        throws IOException;

    
Disconnects this channel's socket.
 The channel's socket is configured so that it can receive datagrams
from, and sends datagrams to, any remote address so long as the security
manager, if installed, permits it.
 This method may be invoked at any time.  It will not have any effect
on read or write operations that are already in progress at the moment
that it is invoked.
 If this channel's socket is not connected, or if the channel is
closed, then invoking this method has no effect.  
Throws:
IOException – 
         If some other I/O error occurs
Returns:
 This datagram channel/**
     * Disconnects this channel's socket.
     *
     * <p> The channel's socket is configured so that it can receive datagrams
     * from, and sends datagrams to, any remote address so long as the security
     * manager, if installed, permits it.
     *
     * <p> This method may be invoked at any time.  It will not have any effect
     * on read or write operations that are already in progress at the moment
     * that it is invoked.
     *
     * <p> If this channel's socket is not connected, or if the channel is
     * closed, then invoking this method has no effect.  </p>
     *
     * @return  This datagram channel
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract DatagramChannel disconnect() throws IOException;

    
Returns the remote address to which this channel's socket is connected.
Throws:
ClosedChannelException – 
         If the channel is closed
IOException – 
         If an I/O error occurs
Returns:
 The remote address; null if the channel's socket is not connected
Since:
1.7/**
     * Returns the remote address to which this channel's socket is connected.
     *
     * @return  The remote address; {@code null} if the channel's socket is not
     *          connected
     *
     * @throws  ClosedChannelException
     *          If the channel is closed
     * @throws  IOException
     *          If an I/O error occurs
     *
     * @since 1.7
     */
    public abstract SocketAddress getRemoteAddress() throws IOException;

    
Receives a datagram via this channel.
 If a datagram is immediately available, or if this channel is in blocking mode and one eventually becomes available, then the datagram is copied into the given byte buffer and its source address is returned. If this channel is in non-blocking mode and a datagram is not immediately available then this method immediately returns null. 
 The datagram is transferred into the given byte buffer starting at its current position, as if by a regular read operation. If there are fewer bytes remaining in the buffer than are required to hold the datagram then the remainder of the datagram is silently discarded. 
 This method performs exactly the same security checks as the receive method of the DatagramSocket class. That is, if the socket is not connected to a specific remote address and a security manager has been installed then for each datagram received this method verifies that the source's address and port number are permitted by the security manager's checkAccept method. The overhead of this security check can be avoided by first connecting the socket via the connect method. 
 This method may be invoked at any time. If another thread has already initiated a read operation upon this channel, however, then an invocation of this method will block until the first operation is complete. If this channel's socket is not bound then this method will first cause the socket to be bound to an address that is assigned automatically, as if invoking the bind method with a parameter of null. 
Params:
dst – 
        The buffer into which the datagram is to be transferred
Throws:
ClosedChannelException – 
         If this channel is closed
AsynchronousCloseException – 
         If another thread closes this channel
         while the read operation is in progress
ClosedByInterruptException – 
         If another thread interrupts the current thread
         while the read operation is in progress, thereby
         closing the channel and setting the current thread's
         interrupt status
SecurityException – 
         If a security manager has been installed
         and it does not permit datagrams to be accepted
         from the datagram's sender
IOException – 
         If some other I/O error occurs
Returns:
 The datagram's source address, or null if this channel is in non-blocking mode and no datagram was immediately available/**
     * Receives a datagram via this channel.
     *
     * <p> If a datagram is immediately available, or if this channel is in
     * blocking mode and one eventually becomes available, then the datagram is
     * copied into the given byte buffer and its source address is returned.
     * If this channel is in non-blocking mode and a datagram is not
     * immediately available then this method immediately returns
     * {@code null}.
     *
     * <p> The datagram is transferred into the given byte buffer starting at
     * its current position, as if by a regular {@link
     * ReadableByteChannel#read(java.nio.ByteBuffer) read} operation.  If there
     * are fewer bytes remaining in the buffer than are required to hold the
     * datagram then the remainder of the datagram is silently discarded.
     *
     * <p> This method performs exactly the same security checks as the {@link
     * java.net.DatagramSocket#receive receive} method of the {@link
     * java.net.DatagramSocket} class.  That is, if the socket is not connected
     * to a specific remote address and a security manager has been installed
     * then for each datagram received this method verifies that the source's
     * address and port number are permitted by the security manager's {@link
     * java.lang.SecurityManager#checkAccept checkAccept} method.  The overhead
     * of this security check can be avoided by first connecting the socket via
     * the {@link #connect connect} method.
     *
     * <p> This method may be invoked at any time.  If another thread has
     * already initiated a read operation upon this channel, however, then an
     * invocation of this method will block until the first operation is
     * complete. If this channel's socket is not bound then this method will
     * first cause the socket to be bound to an address that is assigned
     * automatically, as if invoking the {@link #bind bind} method with a
     * parameter of {@code null}. </p>
     *
     * @param  dst
     *         The buffer into which the datagram is to be transferred
     *
     * @return  The datagram's source address,
     *          or {@code null} if this channel is in non-blocking mode
     *          and no datagram was immediately available
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  AsynchronousCloseException
     *          If another thread closes this channel
     *          while the read operation is in progress
     *
     * @throws  ClosedByInterruptException
     *          If another thread interrupts the current thread
     *          while the read operation is in progress, thereby
     *          closing the channel and setting the current thread's
     *          interrupt status
     *
     * @throws  SecurityException
     *          If a security manager has been installed
     *          and it does not permit datagrams to be accepted
     *          from the datagram's sender
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract SocketAddress receive(ByteBuffer dst) throws IOException;

    
Sends a datagram via this channel.
 If this channel is in non-blocking mode and there is sufficient room
in the underlying output buffer, or if this channel is in blocking mode
and sufficient room becomes available, then the remaining bytes in the
given buffer are transmitted as a single datagram to the given target
address.
 The datagram is transferred from the byte buffer as if by a regular write operation. 
 This method performs exactly the same security checks as the send method of the DatagramSocket class. That is, if the socket is not connected to a specific remote address and a security manager has been installed then for each datagram sent this method verifies that the target address and port number are permitted by the security manager's checkConnect method. The overhead of this security check can be avoided by first connecting the socket via the connect method. 
 This method may be invoked at any time. If another thread has already initiated a write operation upon this channel, however, then an invocation of this method will block until the first operation is complete. If this channel's socket is not bound then this method will first cause the socket to be bound to an address that is assigned automatically, as if by invoking the bind method with a parameter of null. 
Params:
src – 
        The buffer containing the datagram to be sent
target – 
        The address to which the datagram is to be sent
Throws:
AlreadyConnectedException –  If this channel is connected to a different address from that specified by target
ClosedChannelException – 
         If this channel is closed
AsynchronousCloseException – 
         If another thread closes this channel
         while the read operation is in progress
ClosedByInterruptException – 
         If another thread interrupts the current thread
         while the read operation is in progress, thereby
         closing the channel and setting the current thread's
         interrupt status
UnresolvedAddressException – 
         If the given remote address is not fully resolved
UnsupportedAddressTypeException – 
         If the type of the given remote address is not supported
SecurityException – 
         If a security manager has been installed
         and it does not permit datagrams to be sent
         to the given address
IOException – 
         If some other I/O error occurs
Returns:
  The number of bytes sent, which will be either the number
          of bytes that were remaining in the source buffer when this
          method was invoked or, if this channel is non-blocking, may be
          zero if there was insufficient room for the datagram in the
          underlying output buffer/**
     * Sends a datagram via this channel.
     *
     * <p> If this channel is in non-blocking mode and there is sufficient room
     * in the underlying output buffer, or if this channel is in blocking mode
     * and sufficient room becomes available, then the remaining bytes in the
     * given buffer are transmitted as a single datagram to the given target
     * address.
     *
     * <p> The datagram is transferred from the byte buffer as if by a regular
     * {@link WritableByteChannel#write(java.nio.ByteBuffer) write} operation.
     *
     * <p> This method performs exactly the same security checks as the {@link
     * java.net.DatagramSocket#send send} method of the {@link
     * java.net.DatagramSocket} class.  That is, if the socket is not connected
     * to a specific remote address and a security manager has been installed
     * then for each datagram sent this method verifies that the target address
     * and port number are permitted by the security manager's {@link
     * java.lang.SecurityManager#checkConnect checkConnect} method.  The
     * overhead of this security check can be avoided by first connecting the
     * socket via the {@link #connect connect} method.
     *
     * <p> This method may be invoked at any time.  If another thread has
     * already initiated a write operation upon this channel, however, then an
     * invocation of this method will block until the first operation is
     * complete. If this channel's socket is not bound then this method will
     * first cause the socket to be bound to an address that is assigned
     * automatically, as if by invoking the {@link #bind bind} method with a
     * parameter of {@code null}. </p>
     *
     * @param  src
     *         The buffer containing the datagram to be sent
     *
     * @param  target
     *         The address to which the datagram is to be sent
     *
     * @return   The number of bytes sent, which will be either the number
     *           of bytes that were remaining in the source buffer when this
     *           method was invoked or, if this channel is non-blocking, may be
     *           zero if there was insufficient room for the datagram in the
     *           underlying output buffer
     *
     * @throws  AlreadyConnectedException
     *          If this channel is connected to a different address
     *          from that specified by {@code target}
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  AsynchronousCloseException
     *          If another thread closes this channel
     *          while the read operation is in progress
     *
     * @throws  ClosedByInterruptException
     *          If another thread interrupts the current thread
     *          while the read operation is in progress, thereby
     *          closing the channel and setting the current thread's
     *          interrupt status
     *
     * @throws  UnresolvedAddressException
     *          If the given remote address is not fully resolved
     *
     * @throws  UnsupportedAddressTypeException
     *          If the type of the given remote address is not supported
     *
     * @throws  SecurityException
     *          If a security manager has been installed
     *          and it does not permit datagrams to be sent
     *          to the given address
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract int send(ByteBuffer src, SocketAddress target)
        throws IOException;


    // -- ByteChannel operations --

    
Reads a datagram from this channel.
 This method may only be invoked if this channel's socket is connected, and it only accepts datagrams from the socket's peer. If there are more bytes in the datagram than remain in the given buffer then the remainder of the datagram is silently discarded. Otherwise this method behaves exactly as specified in the ReadableByteChannel interface. 
Throws:
NotYetConnectedException – 
         If this channel's socket is not connected/**
     * Reads a datagram from this channel.
     *
     * <p> This method may only be invoked if this channel's socket is
     * connected, and it only accepts datagrams from the socket's peer.  If
     * there are more bytes in the datagram than remain in the given buffer
     * then the remainder of the datagram is silently discarded.  Otherwise
     * this method behaves exactly as specified in the {@link
     * ReadableByteChannel} interface.  </p>
     *
     * @throws  NotYetConnectedException
     *          If this channel's socket is not connected
     */
    public abstract int read(ByteBuffer dst) throws IOException;

    
Reads a datagram from this channel.
 This method may only be invoked if this channel's socket is connected, and it only accepts datagrams from the socket's peer. If there are more bytes in the datagram than remain in the given buffers then the remainder of the datagram is silently discarded. Otherwise this method behaves exactly as specified in the ScatteringByteChannel interface. 
Throws:
NotYetConnectedException – 
         If this channel's socket is not connected/**
     * Reads a datagram from this channel.
     *
     * <p> This method may only be invoked if this channel's socket is
     * connected, and it only accepts datagrams from the socket's peer.  If
     * there are more bytes in the datagram than remain in the given buffers
     * then the remainder of the datagram is silently discarded.  Otherwise
     * this method behaves exactly as specified in the {@link
     * ScatteringByteChannel} interface.  </p>
     *
     * @throws  NotYetConnectedException
     *          If this channel's socket is not connected
     */
    public abstract long read(ByteBuffer[] dsts, int offset, int length)
        throws IOException;

    
Reads a datagram from this channel.
 This method may only be invoked if this channel's socket is connected, and it only accepts datagrams from the socket's peer. If there are more bytes in the datagram than remain in the given buffers then the remainder of the datagram is silently discarded. Otherwise this method behaves exactly as specified in the ScatteringByteChannel interface. 
Throws:
NotYetConnectedException – 
         If this channel's socket is not connected/**
     * Reads a datagram from this channel.
     *
     * <p> This method may only be invoked if this channel's socket is
     * connected, and it only accepts datagrams from the socket's peer.  If
     * there are more bytes in the datagram than remain in the given buffers
     * then the remainder of the datagram is silently discarded.  Otherwise
     * this method behaves exactly as specified in the {@link
     * ScatteringByteChannel} interface.  </p>
     *
     * @throws  NotYetConnectedException
     *          If this channel's socket is not connected
     */
    public final long read(ByteBuffer[] dsts) throws IOException {
        return read(dsts, 0, dsts.length);
    }

    
Writes a datagram to this channel.
 This method may only be invoked if this channel's socket is connected, in which case it sends datagrams directly to the socket's peer. Otherwise it behaves exactly as specified in the WritableByteChannel interface. 
Throws:
NotYetConnectedException – 
         If this channel's socket is not connected/**
     * Writes a datagram to this channel.
     *
     * <p> This method may only be invoked if this channel's socket is
     * connected, in which case it sends datagrams directly to the socket's
     * peer.  Otherwise it behaves exactly as specified in the {@link
     * WritableByteChannel} interface.  </p>
     *
     * @throws  NotYetConnectedException
     *          If this channel's socket is not connected
     */
    public abstract int write(ByteBuffer src) throws IOException;

    
Writes a datagram to this channel.
 This method may only be invoked if this channel's socket is connected, in which case it sends datagrams directly to the socket's peer. Otherwise it behaves exactly as specified in the GatheringByteChannel interface. 
Throws:
NotYetConnectedException – 
         If this channel's socket is not connected
Returns:
  The number of bytes sent, which will be either the number
          of bytes that were remaining in the source buffer when this
          method was invoked or, if this channel is non-blocking, may be
          zero if there was insufficient room for the datagram in the
          underlying output buffer/**
     * Writes a datagram to this channel.
     *
     * <p> This method may only be invoked if this channel's socket is
     * connected, in which case it sends datagrams directly to the socket's
     * peer.  Otherwise it behaves exactly as specified in the {@link
     * GatheringByteChannel} interface.  </p>
     *
     * @return   The number of bytes sent, which will be either the number
     *           of bytes that were remaining in the source buffer when this
     *           method was invoked or, if this channel is non-blocking, may be
     *           zero if there was insufficient room for the datagram in the
     *           underlying output buffer
     *
     * @throws  NotYetConnectedException
     *          If this channel's socket is not connected
     */
    public abstract long write(ByteBuffer[] srcs, int offset, int length)
        throws IOException;

    
Writes a datagram to this channel.
 This method may only be invoked if this channel's socket is connected, in which case it sends datagrams directly to the socket's peer. Otherwise it behaves exactly as specified in the GatheringByteChannel interface. 
Throws:
NotYetConnectedException – 
         If this channel's socket is not connected
Returns:
  The number of bytes sent, which will be either the number
          of bytes that were remaining in the source buffer when this
          method was invoked or, if this channel is non-blocking, may be
          zero if there was insufficient room for the datagram in the
          underlying output buffer/**
     * Writes a datagram to this channel.
     *
     * <p> This method may only be invoked if this channel's socket is
     * connected, in which case it sends datagrams directly to the socket's
     * peer.  Otherwise it behaves exactly as specified in the {@link
     * GatheringByteChannel} interface.  </p>
     *
     * @return   The number of bytes sent, which will be either the number
     *           of bytes that were remaining in the source buffer when this
     *           method was invoked or, if this channel is non-blocking, may be
     *           zero if there was insufficient room for the datagram in the
     *           underlying output buffer
     *
     * @throws  NotYetConnectedException
     *          If this channel's socket is not connected
     */
    public final long write(ByteBuffer[] srcs) throws IOException {
        return write(srcs, 0, srcs.length);
    }

    
{@inheritDoc}
 If there is a security manager set, its checkConnect method is called with the local address and -1 as its arguments to see if the operation is allowed. If the operation is not allowed, a SocketAddress representing the loopback address and the local port of the channel's socket is returned. 
Throws:
ClosedChannelException –     {@inheritDoc}
IOException –                {@inheritDoc}
Returns:
 The SocketAddress that the socket is bound to, or the SocketAddress representing the loopback address if denied by the security manager, or null if the channel's socket is not bound/**
     * {@inheritDoc}
     * <p>
     * If there is a security manager set, its {@code checkConnect} method is
     * called with the local address and {@code -1} as its arguments to see
     * if the operation is allowed. If the operation is not allowed,
     * a {@code SocketAddress} representing the
     * {@link java.net.InetAddress#getLoopbackAddress loopback} address and the
     * local port of the channel's socket is returned.
     *
     * @return  The {@code SocketAddress} that the socket is bound to, or the
     *          {@code SocketAddress} representing the loopback address if
     *          denied by the security manager, or {@code null} if the
     *          channel's socket is not bound
     *
     * @throws  ClosedChannelException     {@inheritDoc}
     * @throws  IOException                {@inheritDoc}
     */
    @Override
    public abstract SocketAddress getLocalAddress() throws IOException;

}