java.lang.Object java.nio.channels.spi.AbstractInterruptibleChannel java.nio.channels.SelectableChannel java.nio.channels.spi.AbstractSelectableChannel java.nio.channels.DatagramChannel
A selectable channel for datagram-oriented sockets.
Datagram channels are not a complete abstraction of network datagram sockets. Binding and the manipulation of socket options must be done through an associated DatagramSocket object obtained by invoking the socket method. It is not possible to create a channel for an arbitrary, pre-existing datagram socket, nor is it possible to specify the DatagramSocketImpl object to be used by a datagram socket associated with a datagram channel.
A datagram channel is created by invoking the open method of this class. 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.
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.
Constructor Summary | |
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protected |
DatagramChannel
(
SelectorProvider
provider) Initializes a new instance of this class. |
Method Summary | |
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abstract DatagramChannel |
connect
(
SocketAddress
remote) Connects this channel's socket. |
abstract DatagramChannel |
disconnect
() Disconnects this channel's socket. |
abstract boolean |
isConnected
() Tells whether or not this channel's socket is connected. |
static DatagramChannel |
open
() Opens a datagram channel. |
abstract int |
read
(
ByteBuffer
dst) Reads a datagram from this channel. |
long |
read
(
ByteBuffer
[] dsts) Reads a datagram from this channel. |
abstract long |
read
(
ByteBuffer
[] dsts, int offset, int length) Reads a datagram from this channel. |
abstract SocketAddress |
receive
(
ByteBuffer
dst) Receives a datagram via this channel. |
abstract int |
send
(
ByteBuffer
src,
SocketAddress
target) Sends a datagram via this channel. |
abstract DatagramSocket |
socket
() Retrieves a datagram socket associated with this channel. |
int |
validOps
() Returns an operation set identifying this channel's supported operations. |
abstract int |
write
(
ByteBuffer
src) Writes a datagram to this channel. |
long |
write
(
ByteBuffer
[] srcs) Writes a datagram to this channel. |
abstract long |
write
(
ByteBuffer
[] srcs, int offset, int length) Writes a datagram to this channel. |
Methods inherited from class java.nio.channels.spi. AbstractSelectableChannel |
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blockingLock , configureBlocking , implCloseChannel , implCloseSelectableChannel , implConfigureBlocking , isBlocking , isRegistered , keyFor , provider , register |
Methods inherited from class java.nio.channels. SelectableChannel |
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register |
Methods inherited from class java.nio.channels.spi. AbstractInterruptibleChannel |
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begin , close , end , isOpen |
Methods inherited from class java.lang. Object |
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clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait |
Methods inherited from interface java.nio.channels. Channel |
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close , isOpen |
Methods inherited from interface java.nio.channels. Channel |
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close , isOpen |
Methods inherited from interface java.nio.channels. Channel |
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close , isOpen |
Methods inherited from interface java.nio.channels. Channel |
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close , isOpen |
Constructor Detail |
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protected DatagramChannel(SelectorProvider provider)
Method Detail |
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public static DatagramChannel open() throws IOException
The new channel is created by invoking the openDatagramChannel method of the system-wide default SelectorProvider object. The channel will not be connected.
public final int validOps()
Datagram channels support reading and writing, so this method returns ( SelectionKey.OP_READ | SelectionKey.OP_WRITE ) .
public abstract DatagramSocket socket()
The returned object will not declare any public methods that are not declared in the DatagramSocket class.
public abstract boolean isConnected()
public abstract DatagramChannel connect(SocketAddress remote) throws IOException
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.
public abstract DatagramChannel disconnect() throws IOException
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.
public abstract SocketAddress receive(ByteBuffer dst) throws IOException
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.
public abstract int send(ByteBuffer src, SocketAddress target) throws IOException
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.
public abstract int read(ByteBuffer dst) throws IOException
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.
public abstract long read(ByteBuffer[] dsts, int offset, int length) throws IOException
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.
public final long read(ByteBuffer[] dsts) throws IOException
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.
public abstract int write(ByteBuffer src) throws IOException
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.
public abstract long write(ByteBuffer[] srcs, int offset, int length) throws IOException
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.
public final long write(ByteBuffer[] srcs) throws IOException
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.