public abstract class DatagramChannel extends AbstractSelectableChannel implements ByteChannel, ScatteringByteChannel, GatheringByteChannel, MulticastChannel
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:
Additional (implementation specific) options may also be supported.
Option Name Description SO_SNDBUFThe size of the socket send buffer SO_RCVBUFThe size of the socket receive buffer SO_REUSEADDRRe-use address SO_BROADCASTAllow transmission of broadcast datagrams IP_TOSThe Type of Service (ToS) octet in the Internet Protocol (IP) header IP_MULTICAST_IFThe network interface for Internet Protocol (IP) multicast datagrams IP_MULTICAST_TTLThe time-to-live for Internet Protocol (IP) multicast datagrams IP_MULTICAST_LOOPLoopback for Internet Protocol (IP) multicast datagrams
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.
| Modifier | Constructor and Description |
|---|---|
protected |
DatagramChannel(SelectorProvider provider)
Initializes a new instance of this class.
|
| Modifier and Type | Method and Description |
|---|---|
abstract DatagramChannel |
bind(SocketAddress local)
Binds the channel's socket to a local address.
|
abstract DatagramChannel |
connect(SocketAddress remote)
Connects this channel's socket.
|
abstract DatagramChannel |
disconnect()
Disconnects this channel's socket.
|
abstract SocketAddress |
getLocalAddress()
Returns the socket address that this channel's socket is bound to.
|
abstract SocketAddress |
getRemoteAddress()
Returns the remote address to which this channel's socket is connected.
|
abstract boolean |
isConnected()
Tells whether or not this channel's socket is connected.
|
static DatagramChannel |
open()
Opens a datagram channel.
|
static DatagramChannel |
open(ProtocolFamily family)
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 <T> DatagramChannel |
setOption(SocketOption<T> name,
T value)
Sets the value of a socket option.
|
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.
|
blockingLock, configureBlocking, implCloseChannel, implCloseSelectableChannel, implConfigureBlocking, isBlocking, isRegistered, keyFor, provider, registerregisterbegin, close, end, isOpenclone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, waitclose, join, joingetOption, supportedOptionsprotected DatagramChannel(SelectorProvider provider)
provider - The provider that created this channelpublic 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.
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 occurspublic static DatagramChannel open(ProtocolFamily family) throws IOException
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 familyUnsupportedOperationException - 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 occurspublic final int validOps()
Datagram channels support reading and writing, so this method
returns (SelectionKey.OP_READ | SelectionKey.OP_WRITE).
validOps in class SelectableChannelpublic abstract DatagramChannel bind(SocketAddress local) throws IOException
NetworkChannel 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 NetworkChannellocal - The address to bind the socket, or null to bind the socket
to an automatically assigned socket addressAlreadyBoundException - If the socket is already boundUnsupportedAddressTypeException - If the type of the given address is not supportedClosedChannelException - If the channel is closedIOException - If some other I/O error occursSecurityException - If a security manager has been installed and its checkListen method denies the
operationNetworkChannel.getLocalAddress()public abstract <T> DatagramChannel setOption(SocketOption<T> name, T value) throws IOException
NetworkChannelsetOption in interface NetworkChannelT - The type of the socket option valuename - The socket optionvalue - 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 channelIllegalArgumentException - If the value is not a valid value for this socket optionClosedChannelException - If this channel is closedIOException - If an I/O error occursStandardSocketOptionspublic abstract DatagramSocket socket()
The returned object will not declare any public methods that are not
declared in the DatagramSocket class.
public abstract boolean isConnected()
true if, and only if, this channel's socket
is open and connectedpublic 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. 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 connectedClosedChannelException - If this channel is closedAsynchronousCloseException - If another thread closes this channel
while the connect operation is in progressClosedByInterruptException - 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 statusSecurityException - If a security manager has been installed
and it does not permit access to the given remote addressIOException - If some other I/O error occurspublic 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.
IOException - If some other I/O error occurspublic abstract SocketAddress getRemoteAddress() throws IOException
null if the channel's socket is not
connectedClosedChannelException - If the channel is closedIOException - If an I/O error occurspublic 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. 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 transferredClosedChannelException - If this channel is closedAsynchronousCloseException - If another thread closes this channel
while the read operation is in progressClosedByInterruptException - 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 statusSecurityException - If a security manager has been installed
and it does not permit datagrams to be accepted
from the datagram's senderIOException - If some other I/O error occurspublic 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. 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 senttarget - The address to which the datagram is to be sentClosedChannelException - If this channel is closedAsynchronousCloseException - If another thread closes this channel
while the read operation is in progressClosedByInterruptException - 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 statusSecurityException - If a security manager has been installed
and it does not permit datagrams to be sent
to the given addressIOException - If some other I/O error occurspublic 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.
read in interface ReadableByteChanneldst - The buffer into which bytes are to be transferredNotYetConnectedException - If this channel's socket is not connectedClosedChannelException - If this channel is closedAsynchronousCloseException - If another thread closes this channel
while the read operation is in progressClosedByInterruptException - 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 statusIOException - If some other I/O error occurspublic 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.
read in interface ScatteringByteChanneldsts - The buffers into which bytes are to be transferredoffset - 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.lengthlength - The maximum number of buffers to be accessed; must be
non-negative and no larger than
dsts.length - offsetNotYetConnectedException - If this channel's socket is not connectedClosedChannelException - If this channel is closedAsynchronousCloseException - If another thread closes this channel
while the read operation is in progressClosedByInterruptException - 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 statusIOException - If some other I/O error occurspublic 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.
read in interface ScatteringByteChanneldsts - The buffers into which bytes are to be transferredNotYetConnectedException - If this channel's socket is not connectedClosedChannelException - If this channel is closedAsynchronousCloseException - If another thread closes this channel
while the read operation is in progressClosedByInterruptException - 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 statusIOException - If some other I/O error occurspublic 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.
write in interface WritableByteChannelsrc - The buffer from which bytes are to be retrievedNotYetConnectedException - If this channel's socket is not connectedClosedChannelException - If this channel is closedAsynchronousCloseException - If another thread closes this channel
while the write operation is in progressClosedByInterruptException - 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 statusIOException - If some other I/O error occurspublic 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.
write in interface GatheringByteChannelsrcs - The buffers from which bytes are to be retrievedoffset - 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.lengthlength - The maximum number of buffers to be accessed; must be
non-negative and no larger than
srcs.length - offsetNotYetConnectedException - If this channel's socket is not connectedClosedChannelException - If this channel is closedAsynchronousCloseException - If another thread closes this channel
while the write operation is in progressClosedByInterruptException - 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 statusIOException - If some other I/O error occurspublic 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.
write in interface GatheringByteChannelsrcs - The buffers from which bytes are to be retrievedNotYetConnectedException - If this channel's socket is not connectedClosedChannelException - If this channel is closedAsynchronousCloseException - If another thread closes this channel
while the write operation is in progressClosedByInterruptException - 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 statusIOException - If some other I/O error occurspublic abstract SocketAddress getLocalAddress() throws IOException
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 NetworkChannelSocketAddress 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 boundClosedChannelException - If the channel is closedIOException - If an I/O error occurs Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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