Class DatagramChannel
- java.lang.Object
-
- java.nio.channels.spi.AbstractInterruptibleChannel
-
- java.nio.channels.SelectableChannel
-
- java.nio.channels.spi.AbstractSelectableChannel
-
- java.nio.channels.DatagramChannel
- All Implemented Interfaces:
-
Closeable
,AutoCloseable
,ByteChannel
,Channel
,GatheringByteChannel
,InterruptibleChannel
,MulticastChannel
,NetworkChannel
,ReadableByteChannel
,ScatteringByteChannel
,WritableByteChannel
public abstract class DatagramChannel extends AbstractSelectableChannel implements ByteChannel, ScatteringByteChannel, GatheringByteChannel, MulticastChannel
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:
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.
- Since:
- 1.4
Constructor Summary
Modifier | Constructor | Description |
---|---|---|
protected | DatagramChannel(SelectorProvider provider) | Initializes a new instance of this class. |
Method Summary
Modifier and Type | Method | 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. |
Methods declared in class java.nio.channels.spi.AbstractSelectableChannel
configureBlocking, implCloseChannel, implCloseSelectableChannel, implConfigureBlocking, provider, register
Methods declared in class java.nio.channels.SelectableChannel
blockingLock, isBlocking, isRegistered, keyFor, register
Methods declared in class java.nio.channels.spi.AbstractInterruptibleChannel
begin, close, end
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods declared in interface java.nio.channels.Channel
isOpen
Methods declared in interface java.nio.channels.MulticastChannel
close, join, join
Methods declared in interface java.nio.channels.NetworkChannel
getOption, supportedOptions
Constructor Detail
DatagramChannel
protected DatagramChannel(SelectorProvider provider)
Initializes a new instance of this class.
- Parameters:
-
provider
- The provider that created this channel
Method Detail
open
public static DatagramChannel open() throws IOException
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.
- Returns:
- A new datagram channel
- Throws:
-
IOException
- If an I/O error occurs
open
public static DatagramChannel open(ProtocolFamily family) throws IOException
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.
- Parameters:
-
family
- The protocol family - Returns:
- A new datagram channel
- Throws:
-
UnsupportedOperationException
- If the specified protocol family is not supported. For example, suppose the parameter is specified asStandardProtocolFamily.INET6
but IPv6 is not enabled on the platform. -
IOException
- If an I/O error occurs - Since:
- 1.7
validOps
public final int validOps()
Returns an operation set identifying this channel's supported operations.
Datagram channels support reading and writing, so this method returns (
SelectionKey.OP_READ
|
SelectionKey.OP_WRITE
)
.
- Specified by:
-
validOps
in classSelectableChannel
- Returns:
- The valid-operation set
bind
public abstract DatagramChannel 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 interfaceNetworkChannel
- Parameters:
-
local
- The address to bind the socket, ornull
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 itscheckListen
method denies the operation - Since:
- 1.7
- See Also:
NetworkChannel.getLocalAddress()
setOption
public abstract <T> DatagramChannel setOption(SocketOption<T> name, T value) throws IOException
Description copied from interface: NetworkChannel
Sets the value of a socket option.
- Specified by:
-
setOption
in interfaceNetworkChannel
- Type Parameters:
-
T
- The type of the socket option value - Parameters:
-
name
- The socket option -
value
- The value of the socket option. A value ofnull
may be a valid value for some socket options. - Returns:
- This channel
- Throws:
-
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 - Since:
- 1.7
- See Also:
StandardSocketOptions
socket
public abstract DatagramSocket socket()
Retrieves a datagram socket associated with this channel.
The returned object will not declare any public methods that are not declared in the DatagramSocket
class.
- Returns:
- A datagram socket associated with this channel
isConnected
public abstract boolean isConnected()
Tells whether or not this channel's socket is connected.
- Returns:
-
true
if, and only if, this channel's socket isopen
and connected
connect
public abstract DatagramChannel 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. 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
.
- Parameters:
-
remote
- The remote address to which this channel is to be connected - Returns:
- This datagram channel
- Throws:
-
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 -
IOException
- If some other I/O error occurs
disconnect
public abstract DatagramChannel 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. 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.
- Returns:
- This datagram channel
- Throws:
-
IOException
- If some other I/O error occurs
getRemoteAddress
public abstract SocketAddress getRemoteAddress() throws IOException
Returns the remote address to which this channel's socket is connected.
- 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 - Since:
- 1.7
receive
public abstract SocketAddress receive(ByteBuffer dst) throws IOException
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. 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
.
- Parameters:
-
dst
- The buffer into which the datagram is to be transferred - Returns:
- The datagram's source address, or
null
if this channel is in non-blocking mode and no datagram was immediately available - Throws:
-
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 a security manager has been installed and it does not permit datagrams to be accepted from the datagram's sender -
IOException
- If some other I/O error occurs
send
public abstract int send(ByteBuffer src, SocketAddress target) throws IOException
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
.
- Parameters:
-
src
- The buffer containing the datagram to be sent -
target
- The address to which the datagram is to be sent - Returns:
- The number of bytes sent, which will be either the number of bytes that were remaining in the source buffer when this method was invoked or, if this channel is non-blocking, may be zero if there was insufficient room for the datagram in the underlying output buffer
- Throws:
-
AlreadyConnectedException
- If this channel is connected to a different address from that specified bytarget
-
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 -
IOException
- If some other I/O error occurs
read
public abstract int read(ByteBuffer dst) throws IOException
Reads a datagram from this channel.
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.
- Specified by:
-
read
in interfaceReadableByteChannel
- Parameters:
-
dst
- The buffer into which bytes are to be transferred - Returns:
- The number of bytes read, possibly zero, or
-1
if the channel has reached end-of-stream - Throws:
-
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
read
public abstract long read(ByteBuffer[] dsts, int offset, int length) throws IOException
Reads a datagram from this channel.
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.
- Specified by:
-
read
in interfaceScatteringByteChannel
- Parameters:
-
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 thandsts.length
-
length
- The maximum number of buffers to be accessed; must be non-negative and no larger thandsts.length
-offset
- Returns:
- The number of bytes read, possibly zero, or
-1
if the channel has reached end-of-stream - Throws:
-
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
read
public final long read(ByteBuffer[] dsts) throws IOException
Reads a datagram from this channel.
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.
- Specified by:
-
read
in interfaceScatteringByteChannel
- Parameters:
-
dsts
- The buffers into which bytes are to be transferred - Returns:
- The number of bytes read, possibly zero, or
-1
if the channel has reached end-of-stream - Throws:
-
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
write
public abstract int write(ByteBuffer src) throws IOException
Writes a datagram to this channel.
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.
- Specified by:
-
write
in interfaceWritableByteChannel
- Parameters:
-
src
- The buffer from which bytes are to be retrieved - Returns:
- The number of bytes written, possibly zero
- Throws:
-
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
write
public abstract long write(ByteBuffer[] srcs, int offset, int length) throws IOException
Writes a datagram to this channel.
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.
- Specified by:
-
write
in interfaceGatheringByteChannel
- Parameters:
-
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 thansrcs.length
-
length
- The maximum number of buffers to be accessed; must be non-negative and no larger thansrcs.length
-offset
- Returns:
- The number of bytes sent, which will be either the number of bytes that were remaining in the source buffer when this method was invoked or, if this channel is non-blocking, may be zero if there was insufficient room for the datagram in the underlying output buffer
- Throws:
-
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
write
public final long write(ByteBuffer[] srcs) throws IOException
Writes a datagram to this channel.
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.
- Specified by:
-
write
in interfaceGatheringByteChannel
- Parameters:
-
srcs
- The buffers from which bytes are to be retrieved - Returns:
- The number of bytes sent, which will be either the number of bytes that were remaining in the source buffer when this method was invoked or, if this channel is non-blocking, may be zero if there was insufficient room for the datagram in the underlying output buffer
- Throws:
-
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
getLocalAddress
public abstract SocketAddress getLocalAddress() throws IOException
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.
- Specified by:
-
getLocalAddress
in interfaceNetworkChannel
- Returns:
- The
SocketAddress
that the socket is bound to, or theSocketAddress
representing the loopback address if denied by the security manager, ornull
if the channel's socket is not bound - Throws:
-
ClosedChannelException
- If the channel is closed -
IOException
- If an I/O error occurs