Closeable, AutoCloseable, ByteChannel, Channel, GatheringByteChannel, InterruptibleChannel, MulticastChannel, NetworkChannel, ReadableByteChannel, ScatteringByteChannel, WritableByteChannel
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 DescriptionSO_SNDBUFThe size of the socket send bufferSO_RCVBUFThe size of the socket receive bufferSO_REUSEADDRRe-use addressSO_BROADCASTAllow transmission of broadcast datagramsIP_TOSThe Type of Service (ToS) octet in the Internet Protocol (IP) headerIP_MULTICAST_IFThe network interface for Internet Protocol (IP) multicast datagramsIP_MULTICAST_TTLThe time-to-live for Internet Protocol (IP) multicast datagramsIP_MULTICAST_LOOPLoopback 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.
Constructors
protected
Initializes a new instance of this class.
Binds the channel's socket to a local address.
Connects this channel's socket.
Disconnects this channel's socket.
Returns the socket address that this channel's socket is bound to.
Returns the remote address to which this channel's socket is connected.
abstract boolean
Tells whether or not this channel's socket is connected.
Opens a datagram channel.
Opens a datagram channel.
abstract int
Reads a datagram from this channel.
long
Reads a datagram from this channel.
abstract long
Reads a datagram from this channel.
Receives a datagram via this channel.
abstract int
Sends a datagram via this channel.
Sets the value of a socket option.
Retrieves a datagram socket associated with this channel.
int
Returns an operation set identifying this channel's supported operations.
abstract int
Writes a datagram to this channel.
long
Writes a datagram to this channel.
abstract long
Writes a datagram to this channel.
Methods declared in class java.lang.Objectclone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, waitInitializes a new instance of this class.
provider - The provider that created this channel
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.
IOException - If an I/O error occurs
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.
family - The protocol family
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
public final int validOps()
Datagram channels support reading and writing, so this method returns (SelectionKey.OP_READ | SelectionKey.OP_WRITE).
validOps in class SelectableChannel
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.
bind in interface NetworkChannel
local - The address to bind the socket, or null to bind the socket to an automatically assigned socket address
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
NetworkChannel.getLocalAddress()
Sets the value of a socket option.
setOption in interface NetworkChannel
T - The type of the socket option value
name - The socket option
value - The value of the socket option. A value of null may be a valid value for some socket options.
UnsupportedOperationException - If the socket option is not supported by this channel
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
StandardSocketOptions
Retrieves a datagram socket associated with this channel.
public abstract boolean isConnected()
Tells whether or not this channel's socket is connected.
true if, and only if, this channel's socket is open and connected
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. Datagrams in the channel's socket receive buffer, which have not been received before invoking this method, may be discarded. The channel's 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. Once connected, no further security checks are performed for datagrams received from, or sent to, the given remote address. Care should be taken to ensure that a connected datagram channel is not shared with untrusted code.
This method may be invoked at any time. If another thread has already initiated a read or write operation upon this channel, then an invocation of this method will block until any such 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.
remote - The remote address to which this channel is to be connected
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, or if unbound, the security manager checkListen method denies the operation
IOException - If some other I/O error occurs
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. If another thread has already initiated a read or write operation upon this channel, then an invocation of this method will block until any such operation is complete.
If this channel's socket is not connected, or if the channel is closed, then invoking this method has no effect.
IOException - If some other I/O error occurs
Returns the remote address to which this channel's socket is connected.
null if the channel's socket is not connected
ClosedChannelException - If the channel is closed
IOException - If an I/O error occurs
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. Datagrams that are not permitted by the security manager are silently discarded. 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.
dst - The buffer into which the datagram is to be transferred
null if this channel is in non-blocking mode and no datagram was immediately available
IllegalArgumentException - If the buffer is read-only
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 unbound, and a security manager has been installed and its checkListen method denies the operation
IOException - If some other I/O error occurs
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.
src - The buffer containing the datagram to be sent
target - The address to which the datagram is to be sent
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, or if unbound, and the security manager's checkListen method denies the operation
IOException - If some other I/O error occurs
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.
read in interface ReadableByteChannel
dst - The buffer into which bytes are to be transferred
-1 if the channel has reached end-of-stream
NotYetConnectedException - If this channel's socket is not connected
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
IOException - If some other I/O error occurs
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.
read in interface ScatteringByteChannel
dsts - The buffers into which bytes are to be transferred
offset - The offset within the buffer array of the first buffer into which bytes are to be transferred; must be non-negative and no larger than dsts.length
length - The maximum number of buffers to be accessed; must be non-negative and no larger than dsts.length - offset
-1 if the channel has reached end-of-stream
NotYetConnectedException - If this channel's socket is not connected
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
IOException - If some other I/O error occurs
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.
read in interface ScatteringByteChannel
dsts - The buffers into which bytes are to be transferred
-1 if the channel has reached end-of-stream
NotYetConnectedException - If this channel's socket is not connected
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
IOException - If some other I/O error occurs
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.
write in interface WritableByteChannel
src - The buffer from which bytes are to be retrieved
NotYetConnectedException - If this channel's socket is not connected
ClosedChannelException - If this channel is closed
AsynchronousCloseException - If another thread closes this channel while the write operation is in progress
ClosedByInterruptException - If another thread interrupts the current thread while the write operation is in progress, thereby closing the channel and setting the current thread's interrupt status
IOException - If some other I/O error occurs
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.
write in interface GatheringByteChannel
srcs - The buffers from which bytes are to be retrieved
offset - The offset within the buffer array of the first buffer from which bytes are to be retrieved; must be non-negative and no larger than srcs.length
length - The maximum number of buffers to be accessed; must be non-negative and no larger than srcs.length - offset
NotYetConnectedException - If this channel's socket is not connected
ClosedChannelException - If this channel is closed
AsynchronousCloseException - If another thread closes this channel while the write operation is in progress
ClosedByInterruptException - If another thread interrupts the current thread while the write operation is in progress, thereby closing the channel and setting the current thread's interrupt status
IOException - If some other I/O error occurs
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.
write in interface GatheringByteChannel
srcs - The buffers from which bytes are to be retrieved
NotYetConnectedException - If this channel's socket is not connected
ClosedChannelException - If this channel is closed
AsynchronousCloseException - If another thread closes this channel while the write operation is in progress
ClosedByInterruptException - If another thread interrupts the current thread while the write operation is in progress, thereby closing the channel and setting the current thread's interrupt status
IOException - If some other I/O error occurs
Returns the socket address that this channel's socket is bound to.
Where the channel is bound to an Internet Protocol socket address then the return value from this method is of type InetSocketAddress.
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.
getLocalAddress in interface NetworkChannel
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
ClosedChannelException - If the channel is closed
IOException - If an I/O error occurs
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