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java.nio.channels
Class AsynchronousDatagramChannel

java.lang.Object
  java.nio.channels.AsynchronousDatagramChannel

All Implemented Interfaces:

Closeable, AsynchronousByteChannel, AsynchronousChannel, Channel, MulticastChannel, NetworkChannel

public abstract class AsynchronousDatagramChannel
extends Object
implements AsynchronousByteChannel, MulticastChannel

An asynchronous channel for datagram-oriented sockets.

An asynchronous datagram channel is created by invoking one of the open methods defined by this class. It is not possible to create a channel for an arbitrary, pre-existing datagram socket. A newly-created asynchronous datagram channel is open but not connected. It 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 that are otherwise performed as part of every send and receive operation when a security manager is set. The 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, an asynchronous datagram channel remains connected until it is disconnected or closed.

Socket options are configured using the setOption method. An asynchronous datagram channel to an Internet Protocol (IP) socket supports the following 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.

Asynchronous datagram channels allow more than one read/receive and write/send to be oustanding at any given time.

Usage Example:

  final AsynchronousDatagramChannel dc = AsynchronousDatagramChannel.open()
      .bind(new InetSocketAddress(4000));

  // print the source address of all packets that we receive
  dc.receive(buffer, buffer, new CompletionHandler<SocketAddress,ByteBuffer>() {
      public void completed(SocketAddress sa, ByteBuffer buffer) {
          System.out.println(sa);
          buffer.clear();
          dc.receive(buffer, buffer, this);
      }
      public void failed(Throwable exc, ByteBuffer buffer) {
          ...
      }
  });
 

Since:

1.7

Constructor Summary

Modifier	Constructor and Description
protected	AsynchronousDatagramChannel(AsynchronousChannelProvider provider) Initializes a new instance of this class.

Method Summary

Modifier and Type	Method and Description
abstract AsynchronousDatagramChannel	bind(SocketAddress local) Binds the channel's socket to a local address.
abstract AsynchronousDatagramChannel	connect(SocketAddress remote) Connects this channel's socket.
abstract AsynchronousDatagramChannel	disconnect() Disconnects this channel's socket.
abstract SocketAddress	getRemoteAddress() Returns the remote address to which this channel is connected.
static AsynchronousDatagramChannel	open() Opens an asynchronous datagram channel.
static AsynchronousDatagramChannel	open(ProtocolFamily family, AsynchronousChannelGroup group) Opens an asynchronous datagram channel.
AsynchronousChannelProvider	provider() Returns the provider that created this channel.
abstract Future<Integer>	read(ByteBuffer dst) Reads a sequence of bytes from this channel into the given buffer.
<A> void	read(ByteBuffer dst, A attachment, CompletionHandler<Integer,? super A> handler) Reads a sequence of bytes from this channel into the given buffer.
abstract <A> void	read(ByteBuffer dst, long timeout, TimeUnit unit, A attachment, CompletionHandler<Integer,? super A> handler) Receives a datagram via this channel.
abstract Future<SocketAddress>	receive(ByteBuffer dst) Receives a datagram via this channel.
<A> void	receive(ByteBuffer dst, A attachment, CompletionHandler<SocketAddress,? super A> handler) Receives a datagram via this channel.
abstract <A> void	receive(ByteBuffer dst, long timeout, TimeUnit unit, A attachment, CompletionHandler<SocketAddress,? super A> handler) Receives a datagram via this channel.
abstract Future<Integer>	send(ByteBuffer src, SocketAddress target) Sends a datagram via this channel.
abstract <A> void	send(ByteBuffer src, SocketAddress target, A attachment, CompletionHandler<Integer,? super A> handler) Sends a datagram via this channel.
abstract <T> AsynchronousDatagramChannel	setOption(SocketOption<T> name, T value) Sets the value of a socket option.
abstract Future<Integer>	write(ByteBuffer src) Writes a sequence of bytes to this channel from the given buffer.
abstract <A> void	write(ByteBuffer src, A attachment, CompletionHandler<Integer,? super A> handler) Writes a sequence of bytes to this channel from the given buffer.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.nio.channels.AsynchronousChannel

close

Methods inherited from interface java.nio.channels.MulticastChannel

close, join, join

Methods inherited from interface java.nio.channels.NetworkChannel

getLocalAddress, getOption, supportedOptions

Methods inherited from interface java.nio.channels.Channel

isOpen

Constructor Detail

AsynchronousDatagramChannel

protected AsynchronousDatagramChannel(AsynchronousChannelProvider provider)

Initializes a new instance of this class.

Method Detail

provider

public final AsynchronousChannelProvider provider()

Returns the provider that created this channel.

open

public static AsynchronousDatagramChannel open(ProtocolFamily family,
                                               AsynchronousChannelGroup group)
                                        throws IOException

Opens an asynchronous datagram channel.

The new channel is created by invoking the openAsynchronousDatagramChannel method on the AsynchronousChannelProvider object that created the given group (or the default provider where group is null).

The family parameter is used to specify the ProtocolFamily. If the datagram channel is to be used for Internet Protocol multicasting then this parameter should correspond to the address type of the multicast groups that this channel will join.

Parameters:

family - The protocol family, or null to use the default protocol family

group - The group to which the newly constructed channel should be bound, or null for the default group

Returns:

A new asynchronous datagram channel

Throws:

UnsupportedOperationException - If the specified protocol family is not supported. For example, suppose the parameter is specified as INET6 but IPv6 is not enabled on the platform.

ShutdownChannelGroupException - The specified group is shutdown

IOException - If an I/O error occurs

open

public static AsynchronousDatagramChannel open()
                                        throws IOException

Opens an asynchronous datagram channel.

This method returns an asynchronous datagram channel that is bound to the default group. This method is equivalent to evaluating the expression:

 open((ProtocolFamily)null, (AsynchronousChannelGroup)null);
 

Returns:

A new asynchronous datagram channel

Throws:

IOException - If an I/O error occurs

bind

public abstract AsynchronousDatagramChannel bind(SocketAddress local)
                                          throws IOException

Description copied from interface: NetworkChannel

Binds the channel's socket to a local address.

This method is used to establish an association between the socket and a local address. Once an association is established then the socket remains bound until the channel is closed. If the local parameter has the value null then the socket will be bound to an address that is assigned automatically.

Specified by:

bind in interface NetworkChannel

Parameters:

local - The address to bind the socket, or null to bind the socket to an automatically assigned socket address

Returns:

This channel

Throws:

AlreadyBoundException - If the socket is already bound

UnsupportedAddressTypeException - If the type of the given address is not supported

ClosedChannelException - If the channel is closed

IOException - If some other I/O error occurs

SecurityException - If a security manager has been installed and its checkListen method denies the operation

See Also:

NetworkChannel.getLocalAddress()

setOption

public abstract <T> AsynchronousDatagramChannel setOption(SocketOption<T> name,
                                                          T value)
                                               throws IOException

Description copied from interface: NetworkChannel

Sets the value of a socket option.

Specified by:

setOption in interface NetworkChannel

Parameters:

name - The socket option

value - The value of the socket option. A value of null may be a valid value for some socket options.

Returns:

This channel

Throws:

IllegalArgumentException - If the value is not a valid value for this socket option

ClosedChannelException - If this channel is closed

IOException - If an I/O error occurs

See Also:

StandardSocketOption

getRemoteAddress

public abstract SocketAddress getRemoteAddress()
                                        throws IOException

Returns the remote address to which this channel is connected.

Where the channel is connected to an Internet Protocol socket address then the return value from this method is of type InetSocketAddress.

Returns:

The remote address; null if the channel's socket is not connected

Throws:

ClosedChannelException - If the channel is closed

IOException - If an I/O error occurs

connect

public abstract AsynchronousDatagramChannel connect(SocketAddress remote)
                                             throws IOException

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. Whether it has any effect on outstanding read or write operations is implementation specific and therefore not specified.

Parameters:

remote - The remote address to which this channel is to be connected

Returns:

This datagram channel

Throws:

ClosedChannelException - If this channel is closed

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

disconnect

public abstract AsynchronousDatagramChannel disconnect()
                                                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. Whether it has any effect on outstanding read or write operations is implementation specific and therefore not specified.

Returns:

This datagram channel

Throws:

IOException - If some other I/O error occurs

receive

public abstract <A> void receive(ByteBuffer dst,
                                 long timeout,
                                 TimeUnit unit,
                                 A attachment,
                                 CompletionHandler<SocketAddress,? super A> handler)

Receives a datagram via this channel.

This method initiates the receiving of a datagram into the given buffer. The handler parameter is a completion handler that is invoked when the receive operation completes (or fails). The result passed to the completion handler is the datagram's source address.

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.

If a timeout is specified and the timeout elapses before the operation completes then the operation completes with the exception InterruptedByTimeoutException. When a timeout elapses then the state of the ByteBuffer is not defined. The buffers should be discarded or at least care must be taken to ensure that the buffer is not accessed while the channel remains open.

When a security manager has been installed and the channel is not connected, then it verifies that the source's address and port number are permitted by the security manager's checkAccept method. The permission check is performed with privileges that are restricted by the calling context of this method. If the permission check fails then the operation completes with a SecurityException. The overhead of this security check can be avoided by first connecting the socket via the connect method.

Parameters:

dst - The buffer into which the datagram is to be transferred

timeout - The timeout, or 0L for no timeout

unit - The time unit of the timeout argument

attachment - The object to attach to the I/O operation; can be null

handler - The handler for consuming the result

Throws:

IllegalArgumentException - If the timeout is negative or the buffer is read-only

ShutdownChannelGroupException - If the channel group has terminated

receive

public final <A> void receive(ByteBuffer dst,
                              A attachment,
                              CompletionHandler<SocketAddress,? super A> handler)

Receives a datagram via this channel.

This method initiates the receiving of a datagram into the given buffer. The handler parameter is a completion handler that is invoked when the receive operation completes (or fails). The result passed to the completion handler is the datagram's source address.

This method is equivalent to invoking receive(ByteBuffer,long,TimeUnit,Object,CompletionHandler) with a timeout of 0L.

Parameters:

dst - The buffer into which the datagram is to be transferred

attachment - The object to attach to the I/O operation; can be null

handler - The handler for consuming the result

Throws:

IllegalArgumentException - If the buffer is read-only

ShutdownChannelGroupException - If the channel group has terminated

receive

public abstract Future<SocketAddress> receive(ByteBuffer dst)

Receives a datagram via this channel.

This method initiates the receiving of a datagram into the given buffer. The method behaves in exactly the same manner as the receive(ByteBuffer,Object,CompletionHandler) method except that instead of specifying a completion handler, this method returns a Future representing the pending result. The Future's get method returns the datagram's source address.

Parameters:

dst - The buffer into which the datagram is to be transferred

Returns:

a Future object representing the pending result

Throws:

IllegalArgumentException - If the buffer is read-only

send

public abstract <A> void send(ByteBuffer src,
                              SocketAddress target,
                              A attachment,
                              CompletionHandler<Integer,? super A> handler)

Sends a datagram via this channel.

This method initiates sending of a datagram from the given buffer to the given address. The handler parameter is a completion handler that is invoked when the send completes (or fails). The result passed to the completion handler is the number of bytes sent.

Otherwise this method works in the same manner as the AsynchronousByteChannel.write(ByteBuffer,Object,CompletionHandler) method.

Parameters:

src - The buffer containing the datagram to be sent

target - The address to which the datagram is to be sent

attachment - The object to attach to the I/O operation; can be null

handler - The handler for consuming the result

Throws:

UnresolvedAddressException - If the given remote address is not fully resolved

UnsupportedAddressTypeException - If the type of the given remote address is not supported

IllegalArgumentException - If the channel's socket is connected and is connected to an address that is not equal to target

SecurityException - If a security manager has been installed and it does not permit datagrams to be sent to the given address

ShutdownChannelGroupException - If the channel group has terminated

send

public abstract Future<Integer> send(ByteBuffer src,
                                     SocketAddress target)

Sends a datagram via this channel.

This method initiates sending of a datagram from the given buffer to the given address. The method behaves in exactly the same manner as the send(ByteBuffer,SocketAddress,Object,CompletionHandler) method except that instead of specifying a completion handler, this method returns a Future representing the pending result. The Future's get method returns the number of bytes sent.

Parameters:

src - The buffer containing the datagram to be sent

target - The address to which the datagram is to be sent

Returns:

a Future object representing the pending result

Throws:

UnresolvedAddressException - If the given remote address is not fully resolved

UnsupportedAddressTypeException - If the type of the given remote address is not supported

IllegalArgumentException - If the channel's socket is connected and is connected to an address that is not equal to target

SecurityException - If a security manager has been installed and it does not permit datagrams to be sent to the given address

read

public abstract <A> void read(ByteBuffer dst,
                              long timeout,
                              TimeUnit unit,
                              A attachment,
                              CompletionHandler<Integer,? super A> handler)

Receives a datagram via this channel.

This method initiates the receiving of a datagram into the given buffer. The handler parameter is a completion handler that is invoked when the receive operation completes (or fails). The result passed to the completion handler is number of bytes read.

This method may only be invoked if this channel is connected, and it only accepts datagrams from the peer that the channel is connected too. The datagram is transferred into the given byte buffer starting at its current position and exactly as specified in the AsynchronousByteChannel interface. 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.

If a timeout is specified and the timeout elapses before the operation completes then the operation completes with the exception InterruptedByTimeoutException. When a timeout elapses then the state of the ByteBuffer is not defined. The buffers should be discarded or at least care must be taken to ensure that the buffer is not accessed while the channel remains open.

Parameters:

dst - The buffer into which the datagram is to be transferred

timeout - The timeout, or 0L for no timeout

unit - The time unit of the timeout argument

attachment - The object to attach to the I/O operation; can be null

handler - The handler for consuming the result

Throws:

IllegalArgumentException - If the timeout is negative or buffer is read-only

NotYetConnectedException - If this channel is not connected

ShutdownChannelGroupException - If the channel group has terminated

read

public final <A> void read(ByteBuffer dst,
                           A attachment,
                           CompletionHandler<Integer,? super A> handler)

Description copied from interface: AsynchronousByteChannel

Reads a sequence of bytes from this channel into the given buffer.

This method initiates an asynchronous read operation to read a sequence of bytes from this channel into the given buffer. The handler parameter is a completion handler that is invoked when the read operation completes (or fails). The result passed to the completion handler is the number of bytes read or -1 if no bytes could be read because the channel has reached end-of-stream.

The read operation may read up to r bytes from the channel, where r is the number of bytes remaining in the buffer, that is, dst.remaining() at the time that the read is attempted. Where r is 0, the read operation completes immediately with a result of 0 without initiating an I/O operation.

Suppose that a byte sequence of length n is read, where 0 < n <= r. This byte sequence will be transferred into the buffer so that the first byte in the sequence is at index p and the last byte is at index p + n - 1, where p is the buffer's position at the moment the read is performed. Upon completion the buffer's position will be equal to p + n; its limit will not have changed.

Buffers are not safe for use by multiple concurrent threads so care should be taken to not access the buffer until the operation has completed.

This method may be invoked at any time. Some channel types may not allow more than one read to be outstanding at any given time. If a thread initiates a read operation before a previous read operation has completed then a ReadPendingException will be thrown.

Specified by:

read in interface AsynchronousByteChannel

Parameters:

dst - The buffer into which bytes are to be transferred

attachment - The object to attach to the I/O operation; can be null

handler - The completion handler

Throws:

NotYetConnectedException - If this channel is not connected

ShutdownChannelGroupException - If the channel group has terminated

read

public abstract Future<Integer> read(ByteBuffer dst)

Description copied from interface: AsynchronousByteChannel

Reads a sequence of bytes from this channel into the given buffer.

This method initiates an asynchronous read operation to read a sequence of bytes from this channel into the given buffer. The method behaves in exactly the same manner as the read(ByteBuffer,Object,CompletionHandler) method except that instead of specifying a completion handler, this method returns a Future representing the pending result. The Future's get method returns the number of bytes read or -1 if no bytes could be read because the channel has reached end-of-stream.

Specified by:

read in interface AsynchronousByteChannel

Parameters:

dst - The buffer into which bytes are to be transferred

Returns:

A Future representing the result of the operation

Throws:

NotYetConnectedException - If this channel is not connected

ShutdownChannelGroupException - If the channel group has terminated

write

public abstract <A> void write(ByteBuffer src,
                               A attachment,
                               CompletionHandler<Integer,? super A> handler)

Description copied from interface: AsynchronousByteChannel

Writes a sequence of bytes to this channel from the given buffer.

This method initiates an asynchronous write operation to write a sequence of bytes to this channel from the given buffer. The handler parameter is a completion handler that is invoked when the write operation completes (or fails). The result passed to the completion handler is the number of bytes written.

The write operation may write up to r bytes to the channel, where r is the number of bytes remaining in the buffer, that is, src.remaining() at the time that the write is attempted. Where r is 0, the write operation completes immediately with a result of 0 without initiating an I/O operation.

Suppose that a byte sequence of length n is written, where 0 < n <= r. This byte sequence will be transferred from the buffer starting at index p, where p is the buffer's position at the moment the write is performed; the index of the last byte written will be p + n - 1. Upon completion the buffer's position will be equal to p + n; its limit will not have changed.

Buffers are not safe for use by multiple concurrent threads so care should be taken to not access the buffer until the operation has completed.

This method may be invoked at any time. Some channel types may not allow more than one write to be outstanding at any given time. If a thread initiates a write operation before a previous write operation has completed then a WritePendingException will be thrown.

Specified by:

write in interface AsynchronousByteChannel

Parameters:

src - The buffer from which bytes are to be retrieved

attachment - The object to attach to the I/O operation; can be null

handler - The completion handler object

Throws:

NotYetConnectedException - If this channel is not connected

ShutdownChannelGroupException - If the channel group has terminated

write

public abstract Future<Integer> write(ByteBuffer src)

Description copied from interface: AsynchronousByteChannel

Writes a sequence of bytes to this channel from the given buffer.

This method initiates an asynchronous write operation to write a sequence of bytes to this channel from the given buffer. The method behaves in exactly the same manner as the write(ByteBuffer,Object,CompletionHandler) method except that instead of specifying a completion handler, this method returns a Future representing the pending result. The Future's get method returns the number of bytes written.

Specified by:

write in interface AsynchronousByteChannel

Parameters:

src - The buffer from which bytes are to be retrieved

Returns:

A Future representing the result of the operation

Throws:

NotYetConnectedException - If this channel is not connected

ShutdownChannelGroupException - If the channel group has terminated