# Class SctpChannel

java.lang.Object
java.nio.channels.spi.AbstractInterruptibleChannel
java.nio.channels.SelectableChannel
java.nio.channels.spi.AbstractSelectableChannel
com.sun.nio.sctp.SctpChannel

All Implemented Interfaces:
  `Closeable, AutoCloseable, Channel, InterruptibleChannel`

public abstract class SctpChannel extends AbstractSelectableChannel
A selectable channel for message-oriented connected SCTP sockets.

An SCTP channel can only control one SCTP association. An `SCTPChannel` is created by invoking one of the `open` methods of this class. A newly-created channel is open but not yet connected, that is, there is no association setup with a remote peer. An attempt to invoke an I/O operation upon an unconnected channel will cause a `NotYetConnectedException` to be thrown. An association can be setup by connecting the channel using one of its `connect` methods. Once connected, the channel remains connected until it is closed. Whether or not a channel is connected may be determined by invoking `getRemoteAddresses`.

SCTP channels support non-blocking connection: A 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 options are configured using the `setOption` method. An SCTP channel support the following options:

> Socket options
> Option Name | Description
> --- | ---
> `SCTP_DISABLE_FRAGMENTS` | Enables or disables message fragmentation
> `SCTP_EXPLICIT_COMPLETE` | Enables or disables explicit message completion
> `SCTP_FRAGMENT_INTERLEAVE` | Controls how the presentation of messages occur for the message receiver
> `SCTP_INIT_MAXSTREAMS` | The maximum number of streams requested by the local endpoint during association initialization
> `SCTP_NODELAY` | Enables or disable a Nagle-like algorithm
> `SCTP_PRIMARY_ADDR` | Requests that the local SCTP stack use the given peer address as the association primary
> `SCTP_SET_PEER_PRIMARY_ADDR` | Requests that the peer mark the enclosed address as the association primary
> `SO_SNDBUF` | The size of the socket send buffer
> `SO_RCVBUF` | The size of the socket receive buffer
> `SO_LINGER` | Linger on close if data is present (when configured in blocking mode only)

Additional (implementation specific) options may also be supported. The list of options supported is obtained by invoking the `supportedOptions` method.

SCTP 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 send or receive operation while an invocation of one of these methods is in progress will block until that invocation is complete.

Since:
  1.7

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `SctpChannel(SelectorProvider provider)`
  Initializes a new instance of this class.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `abstract Association`
  `association()`
  Returns the association on this channel's socket.
  `abstract SctpChannel`
  `bind(SocketAddress local)`
  Binds the channel's socket to a local address.
  `abstract SctpChannel`
  `bindAddress(InetAddress address)`
  Adds the given address to the bound addresses for the channel's socket.
  `abstract boolean`
  `connect(SocketAddress remote)`
  Connects this channel's socket.
  `abstract boolean`
  `connect(SocketAddress remote, int maxOutStreams, int maxInStreams)`
  Connects this channel's socket.
  `abstract boolean`
  `finishConnect()`
  Finishes the process of connecting an SCTP channel.
  `abstract Set<SocketAddress>`
  `getAllLocalAddresses()`
  Returns all of the socket addresses to which this channel's socket is bound.
  `abstract <T> T`
  `getOption(SctpSocketOption<T> name)`
  Returns the value of a socket option.
  `abstract Set<SocketAddress>`
  `getRemoteAddresses()`
  Returns all of the remote addresses to which this channel's socket is connected.
  `abstract boolean`
  `isConnectionPending()`
  Tells whether or not a connection operation is in progress on this channel.
  `static SctpChannel`
  `open()`
  Opens an SCTP channel.
  `static SctpChannel`
  `open(SocketAddress remote, int maxOutStreams, int maxInStreams)`
  Opens an SCTP channel and connects it to a remote address.
  `abstract <T> MessageInfo`
  `receive(ByteBuffer dst, T attachment, NotificationHandler<T> handler)`
  Receives a message into the given buffer and/or handles a notification.
  `abstract int`
  `send(ByteBuffer src, MessageInfo messageInfo)`
  Sends a message via this channel.
  `abstract <T> SctpChannel`
  `setOption(SctpSocketOption<T> name, T value)`
  Sets the value of a socket option.
  `abstract SctpChannel`
  `shutdown()`
  Shutdown a connection without closing the channel.
  `abstract Set<SctpSocketOption<?>>`
  `supportedOptions()`
  Returns a set of the socket options supported by this channel.
  `abstract SctpChannel`
  `unbindAddress(InetAddress address)`
  Removes the given address from the bound addresses for the channel's socket.
  `final int`
  `validOps()`
  Returns an operation set identifying this channel's supported operations.

  ### Methods declared in class AbstractSelectableChannel

  `blockingLock, configureBlocking, implCloseChannel, implCloseSelectableChannel, implConfigureBlocking, isBlocking, isRegistered, keyFor, provider, register`

  ### Methods declared in class SelectableChannel

  `register`

  ### Methods declared in class AbstractInterruptibleChannel

  `begin, close, end, isOpen`

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

  ### Methods declared in interface Channel

  `isOpen`

- ## Constructor Details

  - ### SctpChannel

    protected SctpChannel(SelectorProvider provider)
    Initializes a new instance of this class.
    Parameters:
      `provider` - The selector provider for this channel

- ## Method Details

  - ### open

    public static SctpChannel open() throws IOException
    Opens an SCTP channel.

    The new channel is unbound and unconnected.

    Returns:
      A new SCTP channel
    Throws:
      `UnsupportedOperationException` - If the SCTP protocol is not supported
      `IOException` - If an I/O error occurs

  - ### open

    public static SctpChannel open(SocketAddress remote, int maxOutStreams, int maxInStreams) throws IOException
    Opens an SCTP channel and connects it to a remote address.

    This is a convenience method and is equivalent to evaluating the following expression:

    >     open().connect(remote, maxOutStreams, maxInStreams);

    Parameters:
      `remote` - The remote address to which the new channel is to be connected
      `maxOutStreams` - The number of streams that the application wishes to be able to send to. Must be non negative and no larger than `65536`. `0` to use the endpoints default value.
      `maxInStreams` - The maximum number of inbound streams the application is prepared to support. Must be non negative and no larger than `65536`. `0` to use the endpoints default value.
    Returns:
      A new SCTP channel connected to the given address
    Throws:
      `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
      `UnsupportedOperationException` - If the SCTP protocol is not supported
      `IOException` - If some other I/O error occurs

  - ### association

    public abstract Association association() throws IOException
    Returns the association on this channel's socket.
    Returns:
      the association, or `null` if the channel's socket is not connected.
    Throws:
      `ClosedChannelException` - If the channel is closed
      `IOException` - If some other I/O error occurs

  - ### bind

    public abstract SctpChannel bind(SocketAddress local) throws IOException
    Binds the channel's socket to a local address.

    This method is used to establish a relationship between the socket and the local addresses. Once a relationship is established then the socket remains bound until the channel is closed. This relationship may not necesssarily be with the address `local` as it may be removed by `unbindAddress`, but there will always be at least one local address bound to the channel's socket once an invocation of this method successfully completes.

    Once the channel's socket has been successfully bound to a specific address, that is not automatically assigned, more addresses may be bound to it using `bindAddress`, or removed using `unbindAddress`.

    Parameters:
      `local` - The local address to bind the socket, or `null` to bind the socket to an automatically assigned socket address
    Returns:
      This channel
    Throws:
      `AlreadyConnectedException` - If this channel is already connected
      `ClosedChannelException` - If this channel is closed
      `ConnectionPendingException` - If a non-blocking connection operation is already in progress on this channel
      `AlreadyBoundException` - If this channel is already bound
      `UnsupportedAddressTypeException` - If the type of the given address is not supported
      `IOException` - If some other I/O error occurs

  - ### bindAddress

    public abstract SctpChannel bindAddress(InetAddress address) throws IOException
    Adds the given address to the bound addresses for the channel's socket.

    The given address must not be the `wildcard` address. The channel must be first bound using `bind` before invoking this method, otherwise `NotYetBoundException` is thrown. The `bind` method takes a `SocketAddress` as its argument which typically contains a port number as well as an address. Addresses subquently bound using this method are simply addresses as the SCTP port number remains the same for the lifetime of the channel.

    Adding addresses to a connected association is optional functionality. If the endpoint supports dynamic address reconfiguration then it may send the appropriate message to the peer to change the peers address lists.

    Parameters:
      `address` - The address to add to the bound addresses for the socket
    Returns:
      This channel
    Throws:
      `ClosedChannelException` - If this channel is closed
      `ConnectionPendingException` - If a non-blocking connection operation is already in progress on this channel
      `NotYetBoundException` - If this channel is not yet bound
      `AlreadyBoundException` - If this channel is already bound to the given address
      `IllegalArgumentException` - If address is `null` or the `wildcard` address
      `IOException` - If some other I/O error occurs

  - ### unbindAddress

    public abstract SctpChannel unbindAddress(InetAddress address) throws IOException
    Removes the given address from the bound addresses for the channel's socket.

    The given address must not be the `wildcard` address. The channel must be first bound using `bind` before invoking this method, otherwise `NotYetBoundException` is thrown. If this method is invoked on a channel that does not have `address` as one of its bound addresses or that has only one local address bound to it, then this method throws `IllegalUnbindException`. The initial address that the channel's socket is bound to using `bind` may be removed from the bound addresses for the channel's socket.

    Removing addresses from a connected association is optional functionality. If the endpoint supports dynamic address reconfiguration then it may send the appropriate message to the peer to change the peers address lists.

    Parameters:
      `address` - The address to remove from the bound addresses for the socket
    Returns:
      This channel
    Throws:
      `ClosedChannelException` - If this channel is closed
      `ConnectionPendingException` - If a non-blocking connection operation is already in progress on this channel
      `NotYetBoundException` - If this channel is not yet bound
      `IllegalArgumentException` - If address is `null` or the `wildcard` address
      `IllegalUnbindException` - If `address` is not bound to the channel's socket. or the channel has only one address bound to it
      `IOException` - If some other I/O error occurs

  - ### connect

    public abstract boolean connect(SocketAddress remote) throws IOException
    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 may be invoked at any time. If a `send` or `receive` 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` - The remote peer to which this channel is to be connected
    Returns:
      `true` if a connection was established, `false` if this channel is in non-blocking mode and the connection operation is in progress
    Throws:
      `AlreadyConnectedException` - If this channel is already connected
      `ConnectionPendingException` - If a non-blocking connection operation is already in progress on this channel
      `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
      `IOException` - If some other I/O error occurs

  - ### connect

    public abstract boolean connect(SocketAddress remote, int maxOutStreams, int maxInStreams) throws IOException
    Connects this channel's socket.

    This is a convience method and is equivalent to evaluating the following expression:

    >     setOption(SctpStandardSocketOptions.SCTP_INIT_MAXSTREAMS, SctpStandardSocketOption.InitMaxStreams.create(maxInStreams, maxOutStreams))
    >      .connect(remote);

    The `maxOutStreams` and `maxInStreams` parameters represent the maximum number of streams that the application wishes to be able to send to and receive from. They are negotiated with the remote peer and may be limited by the operating system.

    Parameters:
      `remote` - The remote peer to which this channel is to be connected
      `maxOutStreams` - Must be non negative and no larger than `65536`. `0` to use the endpoints default value.
      `maxInStreams` - Must be non negative and no larger than `65536`. `0` to use the endpoints default value.
    Returns:
      `true` if a connection was established, `false` if this channel is in non-blocking mode and the connection operation is in progress
    Throws:
      `AlreadyConnectedException` - If this channel is already connected
      `ConnectionPendingException` - If a non-blocking connection operation is already in progress on this channel
      `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
      `IOException` - If some other I/O error occurs

  - ### isConnectionPending

    public abstract boolean isConnectionPending()
    Tells whether or not a connection operation is in progress on this channel.
    Returns:
      `true` if, and only if, a connection operation has been initiated on this channel but not yet completed by invoking the `finishConnect()` method

  - ### finishConnect

    public abstract boolean finishConnect() throws IOException
    Finishes the process of connecting an SCTP channel.

    A non-blocking connection operation is initiated by placing a socket channel in non-blocking mode and then invoking one of its `connect` methods. Once the connection is established, or the attempt has failed, the 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 `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 `send` or `receive` 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.

    Returns:
      `true` if, and only if, this channel's socket is now connected
    Throws:
      `NoConnectionPendingException` - If this channel is not connected and a connection operation has not been initiated
      `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
      `IOException` - If some other I/O error occurs

  - ### getAllLocalAddresses

    public abstract Set<SocketAddress> getAllLocalAddresses() throws IOException
    Returns all of the socket addresses to which this channel's socket is bound.
    Returns:
      All the socket addresses that this channel's socket is bound to, or an empty `Set` if the channel's socket is not bound
    Throws:
      `ClosedChannelException` - If the channel is closed
      `IOException` - If an I/O error occurs

  - ### getRemoteAddresses

    public abstract Set<SocketAddress> getRemoteAddresses() throws IOException
    Returns all of the remote addresses to which this channel's socket is connected.

    If the channel is connected to a remote peer that is bound to multiple addresses then it is these addresses that the channel's socket is connected.

    Returns:
      All of the remote addresses to which this channel's socket is connected, or an empty `Set` if the channel's socket is not connected
    Throws:
      `ClosedChannelException` - If the channel is closed
      `IOException` - If an I/O error occurs

  - ### shutdown

    public abstract SctpChannel shutdown() throws IOException
    Shutdown a connection without closing the channel.

    Sends a shutdown command to the remote peer, effectively preventing any new data from being written to the socket by either peer. Further sends will throw `ClosedChannelException`. The channel remains open to allow the for any data (and notifications) to be received that may have been sent by the peer before it received the shutdown command. If the channel is already shutdown then invoking this method has no effect.

    Returns:
      This channel
    Throws:
      `NotYetConnectedException` - If this channel is not yet connected
      `ClosedChannelException` - If this channel is closed
      `IOException` - If some other I/O error occurs

  - ### getOption

    public abstract <T> T getOption(SctpSocketOption<T> name) throws IOException
    Returns the value of a socket option.
    Type Parameters:
      `T` - The type of the socket option value
    Parameters:
      `name` - The socket option
    Returns:
      The value of the socket option. A value of `null` may be a valid value for some socket options.
    Throws:
      `UnsupportedOperationException` - If the socket option is not supported by this channel
      `ClosedChannelException` - If this channel is closed
      `IOException` - If an I/O error occurs
    See Also:
      - `SctpStandardSocketOptions`

  - ### setOption

    public abstract <T> SctpChannel setOption(SctpSocketOption<T> name, T value) throws IOException
    Sets the value of a socket option.
    Type Parameters:
      `T` - The type of the socket option value
    Parameters:
      `name` - The socket option
      `value` - The value of the socket option. A value of `null` 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
    See Also:
      - `SctpStandardSocketOptions`

  - ### supportedOptions

    public abstract Set<SctpSocketOption<?>> 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.

    Returns:
      A set of the socket options supported by this channel

  - ### validOps

    public final int validOps()
    Returns an operation set identifying this channel's supported operations.

    SCTP channels support connecting, reading, and writing, so this method returns `(``SelectionKey.OP_CONNECT` `|` `SelectionKey.OP_READ` `|` `SelectionKey.OP_WRITE``)`.

    Specified by:
      `validOps` in class `SelectableChannel`
    Returns:
      The valid-operation set

  - ### receive

    public abstract <T> MessageInfo receive(ByteBuffer dst, T attachment, NotificationHandler<T> handler) throws IOException
    Receives a message into the given buffer and/or handles a notification.

    If a message or notification is immediately available, or if this channel is in blocking mode and one eventually becomes available, then the message or notification is returned or handled, respectively. If this channel is in non-blocking mode and a message or notification is not immediately available then this method immediately returns `null`.

    If this method receives a message it is copied into the given byte buffer. The message is transferred into the given byte buffer starting at its current position and the buffers position is incremented by the number of bytes read. If there are fewer bytes remaining in the buffer than are required to hold the message, or the underlying input buffer does not contain the complete message, then an invocation of `isComplete` on the returned `MessageInfo` will return `false`, and more invocations of this method will be necessary to completely consume the messgae. Only one message at a time will be partially delivered in any stream. The socket option `SCTP_FRAGMENT_INTERLEAVE` controls various aspects of what interlacing of messages occurs.

    If this method receives a notification then the appropriate method of the given handler, if there is one, is invoked. If the handler returns `CONTINUE` then this method will try to receive another message/notification, otherwise, if `RETURN` is returned this method will return `null`. If an uncaught exception is thrown by the handler it will be propagated up the stack through this method.

    This method may be invoked at any time. If another thread has already initiated a receive operation upon this channel, then an invocation of this method will block until the first operation is complete. The given handler is invoked without holding any locks used to enforce the above synchronization policy, that way handlers will not stall other threads from receiving. A handler should not invoke the `receive` method of this channel, if it does an `IllegalReceiveException` will be thrown.

    Type Parameters:
      `T` - The type of the attachment
    Parameters:
      `dst` - The buffer into which message bytes are to be transferred
      `attachment` - The object to attach to the receive operation; can be `null`
      `handler` - A handler to handle notifications from the SCTP stack, or `null` to ignore any notifications.
    Returns:
      The `MessageInfo`, `null` if this channel is in non-blocking mode and no messages are immediately available or the notification handler returns `RETURN` after handling a notification
    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
      `NotYetConnectedException` - If this channel is not yet connected
      `IllegalReceiveException` - If the given handler invokes the `receive` method of this channel
      `IOException` - If some other I/O error occurs

  - ### send

    public abstract int send(ByteBuffer src, MessageInfo messageInfo) throws IOException
    Sends a message 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 byte buffer are transmitted as a single message. Sending a message is atomic unless explicit message completion `SCTP_EXPLICIT_COMPLETE` socket option is enabled on this channel's socket.

    The message is transferred from the byte buffer as if by a regular `write` operation.

    The bytes will be written to the stream number that is specified by `streamNumber` in the given `messageInfo`.

    This method may be invoked at any time. If another thread has already initiated a send operation upon this channel, then an invocation of this method will block until the first operation is complete.

    Parameters:
      `src` - The buffer containing the message to be sent
      `messageInfo` - Ancillary data about the message to be sent
    Returns:
      The number of bytes sent, which will be either the number of bytes that were remaining in the messages buffer when this method was invoked or, if this channel is non-blocking, may be zero if there was insufficient room for the message in the underlying output buffer
    Throws:
      `InvalidStreamException` - If `streamNumner` is negative or greater than or equal to the maximum number of outgoing streams
      `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
      `NotYetConnectedException` - If this channel is not yet connected
      `IOException` - If some other I/O error occurs