datagramchannel.java

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     * 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. </p>
     *
     * @param  dst
     *         The buffer into which the datagram is to be transferred
     *
     * @return  The datagram's source address,
     *          or <tt>null</tt> 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.
     *
     * <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. </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  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 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.
     *
     * <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.
     *
     * <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.
     *
     * <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.
     *
     * <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.
     *
     * <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.
     *
     * <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);
    }

}