Added in API level 26

AsynchronousSocketChannel

abstract class AsynchronousSocketChannel : AsynchronousByteChannel, NetworkChannel

kotlin.Any
↳	java.nio.channels.AsynchronousSocketChannel

An asynchronous channel for stream-oriented connecting sockets.

Asynchronous socket channels are created in one of two ways. A newly-created AsynchronousSocketChannel is created by invoking one of the #open methods defined by this class. A newly-created channel is open but not yet connected. A connected AsynchronousSocketChannel is created when a connection is made to the socket of an AsynchronousServerSocketChannel. It is not possible to create an asynchronous socket channel for an arbitrary, pre-existing socket.

A newly-created channel is connected by invoking its #connect method; once connected, a channel remains connected until it is closed. Whether or not a socket channel is connected may be determined by invoking its getRemoteAddress method. An attempt to invoke an I/O operation upon an unconnected channel will cause a NotYetConnectedException to be thrown.

Channels of this type are safe for use by multiple concurrent threads. They support concurrent reading and writing, though at most one read operation and one write operation can be outstanding at any time. If a thread initiates a read operation before a previous read operation has completed then a ReadPendingException will be thrown. Similarly, an attempt to initiate a write operation before a previous write has completed will throw a WritePendingException.

Socket options are configured using the setOption method. Asynchronous socket channels support the following options:

Socket options

Option Name	Description
SO_SNDBUF	The size of the socket send buffer
SO_RCVBUF	The size of the socket receive buffer
SO_KEEPALIVE	Keep connection alive
SO_REUSEADDR	Re-use address
TCP_NODELAY	Disable the Nagle algorithm

Additional (implementation specific) options may also be supported.

Timeouts

The read and write methods defined by this class allow a timeout to be specified when initiating a read or write operation. If the timeout elapses before an operation completes then the operation completes with the exception InterruptedByTimeoutException. A timeout may leave the channel, or the underlying connection, in an inconsistent state. Where the implementation cannot guarantee that bytes have not been read from the channel then it puts the channel into an implementation specific error state. A subsequent attempt to initiate a read operation causes an unspecified runtime exception to be thrown. Similarly if a write operation times out and the implementation cannot guarantee bytes have not been written to the channel then further attempts to write to the channel cause an unspecified runtime exception to be thrown. When a timeout elapses then the state of the ByteBuffer, or the sequence of buffers, for the I/O operation is not defined. Buffers should be discarded or at least care must be taken to ensure that the buffers are not accessed while the channel remains open. All methods that accept timeout parameters treat values less than or equal to zero to mean that the I/O operation does not timeout.

Summary

Protected constructors
AsynchronousSocketChannel(provider: AsynchronousChannelProvider!) Initializes a new instance of this class.

Public methods
abstract AsynchronousSocketChannel!	bind(local: SocketAddress!)
abstract Future<Void!>!	connect(remote: SocketAddress!) Connects this channel.
abstract Unit	connect(remote: SocketAddress!, attachment: A, handler: CompletionHandler<Void!, in A>!) Connects this channel.
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.
open static AsynchronousSocketChannel!	open() Opens an asynchronous socket channel.
open static AsynchronousSocketChannel!	open(group: AsynchronousChannelGroup!) Opens an asynchronous socket channel.
AsynchronousChannelProvider!	provider() Returns the provider that created this channel.
abstract Future<Int!>!	read(dst: ByteBuffer!)
Unit	read(dst: ByteBuffer!, attachment: A, handler: CompletionHandler<Int!, in A>!)
abstract Unit	read(dst: ByteBuffer!, timeout: Long, unit: TimeUnit!, attachment: A, handler: CompletionHandler<Int!, in A>!) Reads a sequence of bytes from this channel into the given buffer.
abstract Unit	read(dsts: Array<ByteBuffer!>!, offset: Int, length: Int, timeout: Long, unit: TimeUnit!, attachment: A, handler: CompletionHandler<Long!, in A>!) Reads a sequence of bytes from this channel into a subsequence of the given buffers.
abstract AsynchronousSocketChannel!	setOption(name: SocketOption<T>!, value: T)
abstract AsynchronousSocketChannel!	shutdownInput() Shutdown the connection for reading without closing the channel.
abstract AsynchronousSocketChannel!	shutdownOutput() Shutdown the connection for writing without closing the channel.
abstract Future<Int!>!	write(src: ByteBuffer!)
Unit	write(src: ByteBuffer!, attachment: A, handler: CompletionHandler<Int!, in A>!)
abstract Unit	write(src: ByteBuffer!, timeout: Long, unit: TimeUnit!, attachment: A, handler: CompletionHandler<Int!, in A>!) Writes a sequence of bytes to this channel from the given buffer.
abstract Unit	write(srcs: Array<ByteBuffer!>!, offset: Int, length: Int, timeout: Long, unit: TimeUnit!, attachment: A, handler: CompletionHandler<Long!, in A>!) Writes a sequence of bytes to this channel from a subsequence of the given buffers.

Inherited functions
From class Channel Unit close() Closes this channel. After a channel is closed, any further attempt to invoke I/O operations upon it will cause a ClosedChannelException to be thrown. If this channel is already closed then invoking this method has no effect. This method may be invoked at any time. If some other thread has already invoked it, however, then another invocation will block until the first invocation is complete, after which it will return without effect. Boolean isOpen() Tells whether or not this channel is open.
From class NetworkChannel T getOption(name: SocketOption<T>!) Returns the value of a socket option. MutableSet<SocketOption<*>!>! supportedOptions() Returns a set of the socket options supported by this channel. This method will continue to return the set of options even after the channel has been closed.

Protected constructors

AsynchronousSocketChannel

Added in API level 26

protected AsynchronousSocketChannel(provider: AsynchronousChannelProvider!)

Initializes a new instance of this class.

Parameters
provider	AsynchronousChannelProvider!: The provider that created this channel

Public methods

bind

Added in API level 26

abstract fun bind(local: SocketAddress!): AsynchronousSocketChannel!

Parameters
local	SocketAddress!: The address to bind the socket, or null to bind the socket to an automatically assigned socket address

Return
AsynchronousSocketChannel!	This channel

Exceptions
java.nio.channels.AlreadyBoundException	If the socket is already bound
java.nio.channels.UnsupportedAddressTypeException	If the type of the given address is not supported
java.nio.channels.ClosedChannelException	If the channel is closed
java.io.IOException	If some other I/O error occurs
java.lang.SecurityException	If a security manager has been installed and its checkListen method denies the operation
java.nio.channels.ConnectionPendingException	If a connection operation is already in progress on this channel

connect

Added in API level 26

abstract fun connect(remote: SocketAddress!): Future<Void!>!

Connects this channel.

This method initiates an operation to connect this channel. This method behaves in exactly the same manner as the connect(java.net.SocketAddress,java.lang.Object,java.nio.channels.CompletionHandler) method except that instead of specifying a completion handler, this method returns a Future representing the pending result. The Future's get method returns null on successful completion.

Parameters
remote	SocketAddress!: The remote address to which this channel is to be connected

Return
Future<Void!>!	A Future object representing the pending result

Exceptions
java.nio.channels.UnresolvedAddressException	If the given remote address is not fully resolved
java.nio.channels.UnsupportedAddressTypeException	If the type of the given remote address is not supported
java.nio.channels.AlreadyConnectedException	If this channel is already connected
java.nio.channels.ConnectionPendingException	If a connection operation is already in progress on this channel
java.lang.SecurityException	If a security manager has been installed and it does not permit access to the given remote endpoint

connect

Added in API level 26

abstract fun <A : Any!> connect(
    remote: SocketAddress!, 
    attachment: A, 
    handler: CompletionHandler<Void!, in A>!
): Unit

Connects this channel.

This method initiates an operation to connect this channel. The handler parameter is a completion handler that is invoked when the connection is successfully established or connection cannot be established. If the connection cannot be established then the channel is closed.

This method performs exactly the same security checks as the class. That is, if a security manager has been installed then this method verifies that its java.lang.SecurityManager#checkConnect method permits connecting to the address and port number of the given remote endpoint.

Parameters
<A>	The type of the attachment
remote	SocketAddress!: The remote address to which this channel is to be connected
attachment	A: The object to attach to the I/O operation; can be null
handler	CompletionHandler<Void!, in A>!: The handler for consuming the result

Exceptions
java.nio.channels.UnresolvedAddressException	If the given remote address is not fully resolved
java.nio.channels.UnsupportedAddressTypeException	If the type of the given remote address is not supported
java.nio.channels.AlreadyConnectedException	If this channel is already connected
java.nio.channels.ConnectionPendingException	If a connection operation is already in progress on this channel
java.nio.channels.ShutdownChannelGroupException	If the channel group has terminated
java.lang.SecurityException	If a security manager has been installed and it does not permit access to the given remote endpoint

See Also

• #getRemoteAddress

getLocalAddress

Added in API level 26

abstract fun getLocalAddress(): SocketAddress!

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 .

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.

Return
SocketAddress!	The 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

Exceptions
java.nio.channels.ClosedChannelException	If the channel is closed
java.io.IOException	If an I/O error occurs

getRemoteAddress

Added in API level 26

abstract fun getRemoteAddress(): SocketAddress!

Returns the remote address to which this channel's socket is connected.

Where the channel is bound and connected to an Internet Protocol socket address then the return value from this method is of type .

Return
SocketAddress!	The remote address; null if the channel's socket is not connected

Exceptions
java.nio.channels.ClosedChannelException	If the channel is closed
java.io.IOException	If an I/O error occurs

open

Added in API level 26

open static fun open(): AsynchronousSocketChannel!

Opens an asynchronous socket channel.

This method returns an asynchronous socket channel that is bound to the default group.This method is equivalent to evaluating the expression:

open((AsynchronousChannelGroup)null);
  

Return
AsynchronousSocketChannel!	A new asynchronous socket channel

Exceptions
java.io.IOException	If an I/O error occurs

open

Added in API level 26

open static fun open(group: AsynchronousChannelGroup!): AsynchronousSocketChannel!

Opens an asynchronous socket channel.

The new channel is created by invoking the openAsynchronousSocketChannel method on the AsynchronousChannelProvider that created the group. If the group parameter is null then the resulting channel is created by the system-wide default provider, and bound to the default group.

Parameters
group	AsynchronousChannelGroup!: The group to which the newly constructed channel should be bound, or null for the default group

Return
AsynchronousSocketChannel!	A new asynchronous socket channel

Exceptions
java.nio.channels.ShutdownChannelGroupException	If the channel group is shutdown
java.io.IOException	If an I/O error occurs

provider

Added in API level 26

fun provider(): AsynchronousChannelProvider!

Returns the provider that created this channel.

Return
AsynchronousChannelProvider!	The provider that created this channel

read

Added in API level 26

abstract fun read(dst: ByteBuffer!): Future<Int!>!

Parameters
dst	ByteBuffer!: The buffer into which bytes are to be transferred

Return
Future<Int!>!	A Future representing the result of the operation

Exceptions
java.lang.IllegalArgumentException	If the buffer is read-only
java.nio.channels.ReadPendingException	If the channel does not allow more than one read to be outstanding and a previous read has not completed
java.nio.channels.NotYetConnectedException	If this channel is not yet connected

read

Added in API level 26

fun <A : Any!> read(
    dst: ByteBuffer!, 
    attachment: A, 
    handler: CompletionHandler<Int!, in A>!
): Unit

Parameters
<A>	The type of the attachment
dst	ByteBuffer!: The buffer into which bytes are to be transferred
attachment	A: The object to attach to the I/O operation; can be null
handler	CompletionHandler<Int!, in A>!: The completion handler

Exceptions
java.lang.IllegalArgumentException	If the buffer is read-only
java.nio.channels.ReadPendingException	If the channel does not allow more than one read to be outstanding and a previous read has not completed
java.nio.channels.ShutdownChannelGroupException	If the channel group has terminated
java.nio.channels.NotYetConnectedException	If this channel is not yet connected

read

Added in API level 26

abstract fun <A : Any!> read(
    dst: ByteBuffer!, 
    timeout: Long, 
    unit: TimeUnit!, 
    attachment: A, 
    handler: CompletionHandler<Int!, in A>!
): Unit

Reads a sequence of bytes from this channel into the given buffer.

This method initiates an asynchronous read operation to read a sequence of bytes from this channel into the given buffer. The handler parameter is a completion handler that is invoked when the read operation completes (or fails). The result passed to the completion handler is the number of bytes read or -1 if no bytes could be read because the channel has reached end-of-stream.

If a timeout is specified and the timeout elapses before the operation completes then the operation completes with the exception InterruptedByTimeoutException. Where a timeout occurs, and the implementation cannot guarantee that bytes have not been read, or will not be read from the channel into the given buffer, then further attempts to read from the channel will cause an unspecific runtime exception to be thrown.

Otherwise this method works in the same manner as the java.nio.channels.AsynchronousByteChannel#read(java.nio.ByteBuffer,java.lang.Object,java.nio.channels.CompletionHandler) method.

Parameters
<A>	The type of the attachment
dst	ByteBuffer!: The buffer into which bytes are to be transferred
timeout	Long: The maximum time for the I/O operation to complete
unit	TimeUnit!: The time unit of the timeout argument
attachment	A: The object to attach to the I/O operation; can be null
handler	CompletionHandler<Int!, in A>!: The handler for consuming the result

Exceptions
java.lang.IllegalArgumentException	If the buffer is read-only
java.nio.channels.ReadPendingException	If a read operation is already in progress on this channel
java.nio.channels.NotYetConnectedException	If this channel is not yet connected
java.nio.channels.ShutdownChannelGroupException	If the channel group has terminated

read

Added in API level 26

abstract fun <A : Any!> read(
    dsts: Array<ByteBuffer!>!, 
    offset: Int, 
    length: Int, 
    timeout: Long, 
    unit: TimeUnit!, 
    attachment: A, 
    handler: CompletionHandler<Long!, in A>!
): Unit

Reads a sequence of bytes from this channel into a subsequence of the given buffers. This operation, sometimes called a scattering read, is often useful when implementing network protocols that group data into segments consisting of one or more fixed-length headers followed by a variable-length body. The handler parameter is a completion handler that is invoked when the read operation completes (or fails). The result passed to the completion handler is the number of bytes read or -1 if no bytes could be read because the channel has reached end-of-stream.

This method initiates a read of up to r bytes from this channel, where r is the total number of bytes remaining in the specified subsequence of the given buffer array, that is,

dsts[offset].remaining()
      + dsts[offset+1].remaining()
      + ... + dsts[offset+length-1].remaining()

at the moment that the read is attempted.

Suppose that a byte sequence of length n is read, where 0 < n <= r. Up to the first dsts[offset].remaining() bytes of this sequence are transferred into buffer dsts[offset], up to the next dsts[offset+1].remaining() bytes are transferred into buffer dsts[offset+1], and so forth, until the entire byte sequence is transferred into the given buffers. As many bytes as possible are transferred into each buffer, hence the final position of each updated buffer, except the last updated buffer, is guaranteed to be equal to that buffer's limit. The underlying operating system may impose a limit on the number of buffers that may be used in an I/O operation. Where the number of buffers (with bytes remaining), exceeds this limit, then the I/O operation is performed with the maximum number of buffers allowed by the operating system.

If a timeout is specified and the timeout elapses before the operation completes then it completes with the exception InterruptedByTimeoutException. Where a timeout occurs, and the implementation cannot guarantee that bytes have not been read, or will not be read from the channel into the given buffers, then further attempts to read from the channel will cause an unspecific runtime exception to be thrown.

Parameters
<A>	The type of the attachment
dsts	Array<ByteBuffer!>!: The buffers into which bytes are to be transferred
offset	Int: 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	Int: The maximum number of buffers to be accessed; must be non-negative and no larger than dsts.length - offset
timeout	Long: The maximum time for the I/O operation to complete
unit	TimeUnit!: The time unit of the timeout argument
attachment	A: The object to attach to the I/O operation; can be null
handler	CompletionHandler<Long!, in A>!: The handler for consuming the result

Exceptions
java.lang.IndexOutOfBoundsException	If the pre-conditions for the offset and length parameter aren't met
java.lang.IllegalArgumentException	If the buffer is read-only
java.nio.channels.ReadPendingException	If a read operation is already in progress on this channel
java.nio.channels.NotYetConnectedException	If this channel is not yet connected
java.nio.channels.ShutdownChannelGroupException	If the channel group has terminated

setOption

Added in API level 26

abstract fun <T : Any!> setOption(
    name: SocketOption<T>!, 
    value: T
): AsynchronousSocketChannel!

Parameters
<T>	The type of the socket option value
name	SocketOption<T>!: The socket option
value	T: The value of the socket option. A value of null may be a valid value for some socket options.

Return
AsynchronousSocketChannel!	This channel

Exceptions
java.lang.UnsupportedOperationException	If the socket option is not supported by this channel
java.lang.IllegalArgumentException	If the value is not a valid value for this socket option
java.nio.channels.ClosedChannelException	If this channel is closed
java.io.IOException	If an I/O error occurs

shutdownInput

Added in API level 26

abstract fun shutdownInput(): AsynchronousSocketChannel!

Shutdown the connection for reading without closing the channel.

Once shutdown for reading then further reads on the channel will return -1, the end-of-stream indication. If the input side of the connection is already shutdown then invoking this method has no effect. The effect on an outstanding read operation is system dependent and therefore not specified. The effect, if any, when there is data in the socket receive buffer that has not been read, or data arrives subsequently, is also system dependent.

Return
AsynchronousSocketChannel!	The channel

Exceptions
java.nio.channels.NotYetConnectedException	If this channel is not yet connected
java.nio.channels.ClosedChannelException	If this channel is closed
java.io.IOException	If some other I/O error occurs

shutdownOutput

Added in API level 26

abstract fun shutdownOutput(): AsynchronousSocketChannel!

Shutdown the connection for writing without closing the channel.

Once shutdown for writing then further attempts to write to the channel will throw ClosedChannelException. If the output side of the connection is already shutdown then invoking this method has no effect. The effect on an outstanding write operation is system dependent and therefore not specified.

Return
AsynchronousSocketChannel!	The channel

Exceptions
java.nio.channels.NotYetConnectedException	If this channel is not yet connected
java.nio.channels.ClosedChannelException	If this channel is closed
java.io.IOException	If some other I/O error occurs

write

Added in API level 26

abstract fun write(src: ByteBuffer!): Future<Int!>!

Parameters
src	ByteBuffer!: The buffer from which bytes are to be retrieved

Return
Future<Int!>!	A Future representing the result of the operation

Exceptions
java.nio.channels.WritePendingException	If the channel does not allow more than one write to be outstanding and a previous write has not completed
java.nio.channels.NotYetConnectedException	If this channel is not yet connected

write

Added in API level 26

fun <A : Any!> write(
    src: ByteBuffer!, 
    attachment: A, 
    handler: CompletionHandler<Int!, in A>!
): Unit

Parameters
<A>	The type of the attachment
src	ByteBuffer!: The buffer from which bytes are to be retrieved
attachment	A: The object to attach to the I/O operation; can be null
handler	CompletionHandler<Int!, in A>!: The completion handler object

Exceptions
java.nio.channels.WritePendingException	If the channel does not allow more than one write to be outstanding and a previous write has not completed
java.nio.channels.ShutdownChannelGroupException	If the channel group has terminated
java.nio.channels.NotYetConnectedException	If this channel is not yet connected

write

Added in API level 26

abstract fun <A : Any!> write(
    src: ByteBuffer!, 
    timeout: Long, 
    unit: TimeUnit!, 
    attachment: A, 
    handler: CompletionHandler<Int!, in A>!
): Unit

Writes a sequence of bytes to this channel from the given buffer.

This method initiates an asynchronous write operation to write a sequence of bytes to this channel from the given buffer. The handler parameter is a completion handler that is invoked when the write operation completes (or fails). The result passed to the completion handler is the number of bytes written.

If a timeout is specified and the timeout elapses before the operation completes then it completes with the exception InterruptedByTimeoutException. Where a timeout occurs, and the implementation cannot guarantee that bytes have not been written, or will not be written to the channel from the given buffer, then further attempts to write to the channel will cause an unspecific runtime exception to be thrown.

Otherwise this method works in the same manner as the java.nio.channels.AsynchronousByteChannel#write(java.nio.ByteBuffer,java.lang.Object,java.nio.channels.CompletionHandler) method.

Parameters
<A>	The type of the attachment
src	ByteBuffer!: The buffer from which bytes are to be retrieved
timeout	Long: The maximum time for the I/O operation to complete
unit	TimeUnit!: The time unit of the timeout argument
attachment	A: The object to attach to the I/O operation; can be null
handler	CompletionHandler<Int!, in A>!: The handler for consuming the result

Exceptions
java.nio.channels.WritePendingException	If a write operation is already in progress on this channel
java.nio.channels.NotYetConnectedException	If this channel is not yet connected
java.nio.channels.ShutdownChannelGroupException	If the channel group has terminated

write

Added in API level 26

abstract fun <A : Any!> write(
    srcs: Array<ByteBuffer!>!, 
    offset: Int, 
    length: Int, 
    timeout: Long, 
    unit: TimeUnit!, 
    attachment: A, 
    handler: CompletionHandler<Long!, in A>!
): Unit

Writes a sequence of bytes to this channel from a subsequence of the given buffers. This operation, sometimes called a gathering write, is often useful when implementing network protocols that group data into segments consisting of one or more fixed-length headers followed by a variable-length body. The handler parameter is a completion handler that is invoked when the write operation completes (or fails). The result passed to the completion handler is the number of bytes written.

This method initiates a write of up to r bytes to this channel, where r is the total number of bytes remaining in the specified subsequence of the given buffer array, that is,

srcs[offset].remaining()
      + srcs[offset+1].remaining()
      + ... + srcs[offset+length-1].remaining()

at the moment that the write is attempted.

Suppose that a byte sequence of length n is written, where 0 < n <= r. Up to the first srcs[offset].remaining() bytes of this sequence are written from buffer srcs[offset], up to the next srcs[offset+1].remaining() bytes are written from buffer srcs[offset+1], and so forth, until the entire byte sequence is written. As many bytes as possible are written from each buffer, hence the final position of each updated buffer, except the last updated buffer, is guaranteed to be equal to that buffer's limit. The underlying operating system may impose a limit on the number of buffers that may be used in an I/O operation. Where the number of buffers (with bytes remaining), exceeds this limit, then the I/O operation is performed with the maximum number of buffers allowed by the operating system.

If a timeout is specified and the timeout elapses before the operation completes then it completes with the exception InterruptedByTimeoutException. Where a timeout occurs, and the implementation cannot guarantee that bytes have not been written, or will not be written to the channel from the given buffers, then further attempts to write to the channel will cause an unspecific runtime exception to be thrown.

Parameters
<A>	The type of the attachment
srcs	Array<ByteBuffer!>!: The buffers from which bytes are to be retrieved
offset	Int: 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	Int: The maximum number of buffers to be accessed; must be non-negative and no larger than srcs.length - offset
timeout	Long: The maximum time for the I/O operation to complete
unit	TimeUnit!: The time unit of the timeout argument
attachment	A: The object to attach to the I/O operation; can be null
handler	CompletionHandler<Long!, in A>!: The handler for consuming the result

Exceptions
java.lang.IndexOutOfBoundsException	If the pre-conditions for the offset and length parameter aren't met
java.nio.channels.WritePendingException	If a write operation is already in progress on this channel
java.nio.channels.NotYetConnectedException	If this channel is not yet connected
java.nio.channels.ShutdownChannelGroupException	If the channel group has terminated