Added in API level 1

SocketChannel

abstract class SocketChannel : AbstractSelectableChannel, ByteChannel, ScatteringByteChannel, GatheringByteChannel, NetworkChannel
kotlin.Any
   ↳ java.nio.channels.spi.AbstractInterruptibleChannel
   ↳ java.nio.channels.SelectableChannel
   ↳ java.nio.channels.spi.AbstractSelectableChannel
   ↳ java.nio.channels.SocketChannel

A selectable channel for stream-oriented connecting sockets.

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

Socket channels support non-blocking connection: A socket channel may be created and the process of establishing the link to the remote socket may be initiated via the connect method for later completion by the finishConnect method. Whether or not a connection operation is in progress may be determined by invoking the isConnectionPending method.

Socket channels support asynchronous shutdown, which is similar to the asynchronous close operation specified in the Channel class. If the input side of a socket is shut down by one thread while another thread is blocked in a read operation on the socket's channel, then the read operation in the blocked thread will complete without reading any bytes and will return -1. If the output side of a socket is shut down by one thread while another thread is blocked in a write operation on the socket's channel, then the blocked thread will receive an AsynchronousCloseException.

Socket options are configured using the setOption method. 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
SO_LINGER Linger on close if data is present (when configured in blocking mode only)
TCP_NODELAY Disable the Nagle algorithm
Additional (implementation specific) options may also be supported.

Socket 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. The connect and finishConnect methods are mutually synchronized against each other, and an attempt to initiate a read or write operation while an invocation of one of these methods is in progress will block until that invocation is complete.

Summary

Protected constructors

Initializes a new instance of this class.

Public methods
abstract SocketChannel!

abstract Boolean

Connects this channel's socket.

abstract Boolean

Finishes the process of connecting a socket channel.

abstract SocketAddress!

Returns the socket address that this channel's socket is bound to.

abstract SocketAddress!

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

abstract Boolean

Tells whether or not this channel's network socket is connected.

abstract Boolean

Tells whether or not a connection operation is in progress on this channel.

open static SocketChannel!

Opens a socket channel.

open static SocketChannel!
open(remote: SocketAddress!)

Opens a socket channel and connects it to a remote address.

abstract Int

abstract Long
read(dsts: Array<ByteBuffer!>!, offset: Int, length: Int)

Long
read(dsts: Array<ByteBuffer!>!)

abstract SocketChannel!
setOption(name: SocketOption<T>!, value: T)

abstract SocketChannel!

Shutdown the connection for reading without closing the channel.

abstract SocketChannel!

Shutdown the connection for writing without closing the channel.

abstract Socket!

Retrieves a socket associated with this channel.

Int

Returns an operation set identifying this channel's supported operations.

abstract Int

abstract Long
write(srcs: Array<ByteBuffer!>!, offset: Int, length: Int)

Long

Inherited functions

Protected constructors

SocketChannel

Added in API level 1
protected SocketChannel(provider: SelectorProvider!)

Initializes a new instance of this class.

Parameters
provider SelectorProvider!: The provider that created this channel

Public methods

bind

Added in API level 24
abstract fun bind(local: SocketAddress!): SocketChannel!
Parameters
local SocketAddress!: The address to bind the socket, or null to bind the socket to an automatically assigned socket address
Return
SocketChannel! 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 non-blocking connect operation is already in progress on this channel

connect

Added in API level 1
abstract fun connect(remote: SocketAddress!): Boolean

Connects this channel's socket.

If this channel is in non-blocking mode then an invocation of this method initiates a non-blocking connection operation. If the connection is established immediately, as can happen with a local connection, then this method returns true. Otherwise this method returns false and the connection operation must later be completed by invoking the finishConnect method.

If this channel is in blocking mode then an invocation of this method will block until the connection is established or an I/O error occurs.

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.

This method may be invoked at any time. If a read or write operation upon this channel is invoked while an invocation of this method is in progress then that operation will first block until this invocation is complete. If a connection attempt is initiated but fails, that is, if an invocation of this method throws a checked exception, then the channel will be closed.

Parameters
remote SocketAddress!: The remote address to which this channel is to be connected
Return
Boolean true if a connection was established, false if this channel is in non-blocking mode and the connection operation is in progress
Exceptions
java.nio.channels.AlreadyConnectedException If this channel is already connected
java.nio.channels.ConnectionPendingException If a non-blocking connection operation is already in progress on this channel
java.nio.channels.ClosedChannelException If this channel is closed
java.nio.channels.AsynchronousCloseException If another thread closes this channel while the connect operation is in progress
java.nio.channels.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
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.lang.SecurityException If a security manager has been installed and it does not permit access to the given remote endpoint
java.io.IOException If some other I/O error occurs

finishConnect

Added in API level 1
abstract fun finishConnect(): Boolean

Finishes the process of connecting a socket channel.

A non-blocking connection operation is initiated by placing a socket channel in non-blocking mode and then invoking its connect method. Once the connection is established, or the attempt has failed, the socket channel will become connectable and this method may be invoked to complete the connection sequence. If the connection operation failed then invoking this method will cause an appropriate java.io.IOException to be thrown.

If this channel is already connected then this method will not block and will immediately return true. If this channel is in non-blocking mode then this method will return false if the connection process is not yet complete. If this channel is in blocking mode then this method will block until the connection either completes or fails, and will always either return true or throw a checked exception describing the failure.

This method may be invoked at any time. If a read or write operation upon this channel is invoked while an invocation of this method is in progress then that operation will first block until this invocation is complete. If a connection attempt fails, that is, if an invocation of this method throws a checked exception, then the channel will be closed.

Return
Boolean true if, and only if, this channel's socket is now connected
Exceptions
java.nio.channels.NoConnectionPendingException If this channel is not connected and a connection operation has not been initiated
java.nio.channels.ClosedChannelException If this channel is closed
java.nio.channels.AsynchronousCloseException If another thread closes this channel while the connect operation is in progress
java.nio.channels.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
java.io.IOException If some other I/O error occurs

getLocalAddress

Added in API level 24
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 24
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

isConnected

Added in API level 1
abstract fun isConnected(): Boolean

Tells whether or not this channel's network socket is connected.

Return
Boolean true if, and only if, this channel's network socket is open and connected

isConnectionPending

Added in API level 1
abstract fun isConnectionPending(): Boolean

Tells whether or not a connection operation is in progress on this channel.

Return
Boolean true if, and only if, a connection operation has been initiated on this channel but not yet completed by invoking the finishConnect method

open

Added in API level 1
open static fun open(): SocketChannel!

Opens a socket channel.

The new channel is created by invoking the openSocketChannel method of the system-wide default object.

Return
SocketChannel! A new socket channel
Exceptions
java.io.IOException If an I/O error occurs

open

Added in API level 1
open static fun open(remote: SocketAddress!): SocketChannel!

Opens a socket channel and connects it to a remote address.

This convenience method works as if by invoking the open() method, invoking the connect method upon the resulting socket channel, passing it remote, and then returning that channel.

Parameters
remote SocketAddress!: The remote address to which the new channel is to be connected
Return
SocketChannel! A new, and connected, socket channel
Exceptions
java.nio.channels.AsynchronousCloseException If another thread closes this channel while the connect operation is in progress
java.nio.channels.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
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.lang.SecurityException If a security manager has been installed and it does not permit access to the given remote endpoint
java.io.IOException If some other I/O error occurs

read

Added in API level 1
abstract fun read(dst: ByteBuffer!): Int
Parameters
dst ByteBuffer!: The buffer into which bytes are to be transferred
Return
Int The number of bytes read, possibly zero, or -1 if the channel has reached end-of-stream
Exceptions
java.nio.channels.NonReadableChannelException If this channel was not opened for reading
java.nio.channels.ClosedChannelException If this channel is closed
java.nio.channels.AsynchronousCloseException If another thread closes this channel while the read operation is in progress
java.nio.channels.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
java.io.IOException If some other I/O error occurs
java.nio.channels.NotYetConnectedException If this channel is not yet connected

read

Added in API level 1
abstract fun read(
    dsts: Array<ByteBuffer!>!,
    offset: Int,
    length: Int
): Long
Parameters
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
Return
Long The number of bytes read, possibly zero, or -1 if the channel has reached end-of-stream
Exceptions
java.lang.IndexOutOfBoundsException If the preconditions on the offset and length parameters do not hold
java.nio.channels.NonReadableChannelException If this channel was not opened for reading
java.nio.channels.ClosedChannelException If this channel is closed
java.nio.channels.AsynchronousCloseException If another thread closes this channel while the read operation is in progress
java.nio.channels.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
java.io.IOException If some other I/O error occurs
java.nio.channels.NotYetConnectedException If this channel is not yet connected

read

Added in API level 1
fun read(dsts: Array<ByteBuffer!>!): Long
Parameters
dsts Array<ByteBuffer!>!: The buffers into which bytes are to be transferred
Return
Long The number of bytes read, possibly zero, or -1 if the channel has reached end-of-stream
Exceptions
java.nio.channels.NonReadableChannelException If this channel was not opened for reading
java.nio.channels.ClosedChannelException If this channel is closed
java.nio.channels.AsynchronousCloseException If another thread closes this channel while the read operation is in progress
java.nio.channels.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
java.io.IOException If some other I/O error occurs
java.nio.channels.NotYetConnectedException If this channel is not yet connected

setOption

Added in API level 24
abstract fun <T : Any!> setOption(
    name: SocketOption<T>!,
    value: T
): SocketChannel!
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
SocketChannel! 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 24
abstract fun shutdownInput(): SocketChannel!

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.

Return
SocketChannel! 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 24
abstract fun shutdownOutput(): SocketChannel!

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.

Return
SocketChannel! 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

socket

Added in API level 1
abstract fun socket(): Socket!

Retrieves a socket associated with this channel.

The returned object will not declare any public methods that are not declared in the java.net.Socket class.

Return
Socket! A socket associated with this channel

validOps

Added in API level 1
fun validOps(): Int

Returns an operation set identifying this channel's supported operations.

Socket channels support connecting, reading, and writing, so this method returns (SelectionKey#OP_CONNECT | SelectionKey#OP_READ | java.nio.channels.SelectionKey#OP_WRITE).

Return
Int The valid-operation set

write

Added in API level 1
abstract fun write(src: ByteBuffer!): Int
Parameters
src ByteBuffer!: The buffer from which bytes are to be retrieved
Return
Int The number of bytes written, possibly zero
Exceptions
java.nio.channels.NonWritableChannelException If this channel was not opened for writing
java.nio.channels.ClosedChannelException If this channel is closed
java.nio.channels.AsynchronousCloseException If another thread closes this channel while the write operation is in progress
java.nio.channels.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
java.io.IOException If some other I/O error occurs
java.nio.channels.NotYetConnectedException If this channel is not yet connected

write

Added in API level 1
abstract fun write(
    srcs: Array<ByteBuffer!>!,
    offset: Int,
    length: Int
): Long
Parameters
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
Return
Long The number of bytes written, possibly zero
Exceptions
java.lang.IndexOutOfBoundsException If the preconditions on the offset and length parameters do not hold
java.nio.channels.NonWritableChannelException If this channel was not opened for writing
java.nio.channels.ClosedChannelException If this channel is closed
java.nio.channels.AsynchronousCloseException If another thread closes this channel while the write operation is in progress
java.nio.channels.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
java.io.IOException If some other I/O error occurs
java.nio.channels.NotYetConnectedException If this channel is not yet connected

write

Added in API level 1
fun write(srcs: Array<ByteBuffer!>!): Long
Parameters
srcs Array<ByteBuffer!>!: The buffers from which bytes are to be retrieved
Return
Long The number of bytes written, possibly zero
Exceptions
java.nio.channels.NonWritableChannelException If this channel was not opened for writing
java.nio.channels.ClosedChannelException If this channel is closed
java.nio.channels.AsynchronousCloseException If another thread closes this channel while the write operation is in progress
java.nio.channels.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
java.io.IOException If some other I/O error occurs
java.nio.channels.NotYetConnectedException If this channel is not yet connected