Closeable
, AutoCloseable
, ByteChannel
, Channel
, GatheringByteChannel
, InterruptibleChannel
, MulticastChannel
, NetworkChannel
, ReadableByteChannel
, ScatteringByteChannel
, WritableByteChannel
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_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
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 | Description |
---|---|---|
protected |
Initializes a new instance of this class. |
Modifier and Type | Method | Description |
---|---|---|
abstract DatagramChannel |
bind |
Binds the channel's socket to a local address. |
abstract DatagramChannel |
connect |
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 |
Opens a datagram channel. |
abstract int |
read |
Reads a datagram from this channel. |
final long |
read |
Reads a datagram from this channel. |
abstract long |
read |
Reads a datagram from this channel. |
abstract SocketAddress |
receive |
Receives a datagram via this channel. |
abstract int |
send |
Sends a datagram via this channel. |
abstract <T> DatagramChannel |
setOption |
Sets the value of a socket option. |
abstract DatagramSocket |
socket() |
Retrieves a datagram socket associated with this channel. |
final int |
validOps() |
Returns an operation set identifying this channel's supported operations. |
abstract int |
write |
Writes a datagram to this channel. |
final long |
write |
Writes a datagram to this channel. |
abstract long |
write |
Writes a datagram to this channel. |
blockingLock, configureBlocking, implCloseChannel, implCloseSelectableChannel, implConfigureBlocking, isBlocking, isRegistered, keyFor, provider, register
register
begin, close, end, isOpen
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
close, join, join
getOption, supportedOptions
protected 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 SelectableChannel
public 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 NetworkChannel
local
- 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 operationpublic abstract <T> DatagramChannel setOption(SocketOption<T> name, T value) throws IOException
NetworkChannel
setOption
in interface NetworkChannel
T
- 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 occurspublic abstract DatagramSocket socket()
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. 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 connectedAlreadyConnectedException
- If this channel is already 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 statusUnresolvedAddressException
- If the given remote address is not fully resolvedUnsupportedAddressTypeException
- If the type of the given remote address is not supportedSecurityException
- 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 operationIOException
- 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. 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 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. 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 transferrednull
if this channel is in non-blocking mode and no datagram was immediately availableIllegalArgumentException
- If the buffer is read-onlyClosedChannelException
- 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 unbound, and a security manager has been installed and its checkListen
method denies the operationIOException
- 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 sentAlreadyConnectedException
- If this channel is connected to a different address from that specified by target
ClosedChannelException
- 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 statusUnresolvedAddressException
- If the given remote address is not fully resolvedUnsupportedAddressTypeException
- If the type of the given remote address is not supportedSecurityException
- 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 operationIOException
- 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 ReadableByteChannel
dst
- The buffer into which bytes are to be transferred-1
if the channel has reached end-of-streamNotYetConnectedException
- 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 ScatteringByteChannel
dsts
- 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.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-streamNotYetConnectedException
- 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 ScatteringByteChannel
dsts
- The buffers into which bytes are to be transferred-1
if the channel has reached end-of-streamNotYetConnectedException
- 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 WritableByteChannel
src
- 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 GatheringByteChannel
srcs
- 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.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 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 GatheringByteChannel
srcs
- 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 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 boundClosedChannelException
- If the channel is closedIOException
- If an I/O error occurs
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Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/nio/channels/DatagramChannel.html