Module java.base

Package java.nio.channels

Class ServerSocketChannel

java.lang.Object

java.nio.channels.spi.AbstractInterruptibleChannel

java.nio.channels.SelectableChannel

java.nio.channels.spi.AbstractSelectableChannel

java.nio.channels.ServerSocketChannel

All Implemented Interfaces:

Closeable, AutoCloseable, Channel, InterruptibleChannel, NetworkChannel

public abstract class ServerSocketChannel
extends AbstractSelectableChannel
implements NetworkChannel

A selectable channel for stream-oriented listening sockets.

A server-socket channel is created by invoking one of the open methods of this class. The no-arg open method opens a server-socket channel for an Internet protocol socket. The open(ProtocolFamily) method is used to open a server-socket channel for a socket of a specified protocol family. It is not possible to create a channel for an arbitrary, pre-existing socket. A newly-created server-socket channel is open but not yet bound. An attempt to invoke the accept method of an unbound server-socket channel will cause a NotYetBoundException to be thrown. A server-socket channel can be bound by invoking one of the bind methods defined by this class.

Socket options are configured using the setOption method. Server-socket channels for Internet protocol sockets support the following options:

Socket options

Option Name	Description
SO_RCVBUF	The size of the socket receive buffer
SO_REUSEADDR	Re-use address

Server-socket channels for Unix domain sockets support:

Socket options

Option Name	Description
SO_RCVBUF	The size of the socket receive buffer

Additional (implementation specific) options may also be supported.

Server-socket channels are safe for use by multiple concurrent threads.

Since:

1.4

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method	Description
abstract SocketChannel	accept()	Accepts a connection made to this channel's socket.
final ServerSocketChannel	bind(SocketAddress local)	Binds the channel's socket to a local address and configures the socket to listen for connections.
abstract ServerSocketChannel	bind(SocketAddress local, int backlog)	Binds the channel's socket to a local address and configures the socket to listen for connections.
abstract SocketAddress	getLocalAddress()	Returns the socket address that this channel's socket is bound to.
static ServerSocketChannel	open()	Opens a server-socket channel for an Internet protocol socket.
static ServerSocketChannel	open(ProtocolFamily family)	Opens a server-socket channel.
abstract <T> ServerSocketChannel	setOption(SocketOption<T> name, T value)	Sets the value of a socket option.
abstract ServerSocket	socket()	Retrieves a server socket associated with this channel.
final int	validOps()	Returns an operation set identifying this channel's supported operations.

Methods declared in class java.nio.channels.spi.AbstractSelectableChannel

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

Methods declared in class java.nio.channels.SelectableChannel

register

Methods declared in class java.nio.channels.spi.AbstractInterruptibleChannel

begin, close, end, isOpen

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.NetworkChannel

getOption, supportedOptions

Constructor Details

ServerSocketChannel

protected ServerSocketChannel(SelectorProvider provider)

Initializes a new instance of this class.

Parameters:

provider - The provider that created this channel

Method Details

open

public static ServerSocketChannel open()
                                throws IOException

Opens a server-socket channel for an Internet protocol socket.

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

The new channel's socket is initially unbound; it must be bound to a specific address via one of its socket's bind methods before connections can be accepted.

Returns:

A new socket channel

Throws:

IOException - If an I/O error occurs

See Also:

• java.net.preferIPv4Stack system property

open

public static ServerSocketChannel open(ProtocolFamily family)
                                throws IOException

Opens a server-socket channel. The family parameter specifies the protocol family of the channel's socket.

The new channel is created by invoking the openServerSocketChannel(ProtocolFamily) method of the system-wide default SelectorProvider object.

Parameters:

family - The protocol family

Returns:

A new socket channel

Throws:

UnsupportedOperationException - If the specified protocol family is not supported. For example, suppose the parameter is specified as StandardProtocolFamily.INET6 but IPv6 is not enabled on the platform.

IOException - If an I/O error occurs

Since:

15

See Also:

• java.net.preferIPv4Stack system property

validOps

public final int validOps()

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

Server-socket channels only support the accepting of new connections, so this method returns SelectionKey.OP_ACCEPT.

Specified by:

validOps in class SelectableChannel

Returns:

The valid-operation set

bind

public final ServerSocketChannel bind(SocketAddress local)
                               throws IOException

Binds the channel's socket to a local address and configures the socket to listen for connections.

An invocation of this method is equivalent to the following:

    bind(local, 0);

Specified by:

bind in interface NetworkChannel

Parameters:

local - The local address to bind the socket, or null to bind 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 it denies the operation

Since:

1.7

See Also:

• NetworkChannel.getLocalAddress()

bind

public abstract ServerSocketChannel bind(SocketAddress local,
 int backlog)
                                  throws IOException

Binds the channel's socket to a local address and configures the socket to listen for connections.

This method is used to establish an association between the socket and a local address. For Internet protocol sockets, once an association is established then the socket remains bound until the channel is closed.

The backlog parameter is the maximum number of pending connections on the socket. Its exact semantics are implementation specific. In particular, an implementation may impose a maximum length or may choose to ignore the parameter altogether. If the backlog parameter has the value 0, or a negative value, then an implementation specific default is used.

API Note:

Binding a server socket channel for a Unix Domain socket, creates a file corresponding to the file path in the UnixDomainSocketAddress. This file persists after the channel is closed, and must be removed before another socket can bind to the same name. Binding to a null address causes the socket to be automatically bound to some unique file in a system temporary location. The associated socket file also persists after the channel is closed. Its name can be obtained from the channel's local socket address.

Implementation Note:

Each platform enforces an implementation specific, maximum length for the name of a Unix Domain socket. This limitation is enforced when a channel is bound. The maximum length is typically close to and generally not less than 100 bytes. This limitation also applies to automatically bound server socket channels. See the Unix domain networking properties that can be used to select the temporary directory where these sockets are created.

Parameters:

local - The address to bind the socket, or null to bind to an automatically assigned socket address

backlog - The maximum number of pending connections

Returns:

This channel

Throws:

AlreadyBoundException - If the socket is already bound

UnsupportedAddressTypeException - If the type of the given address is not supported

ClosedChannelException - If this channel is closed

IOException - If some other I/O error occurs

SecurityException - If a security manager has been installed and its checkListen method denies the operation for an Internet protocol socket address, or for a Unix domain socket address if it denies NetPermission("accessUnixDomainSocket").

Since:

1.7

setOption

public abstract <T> ServerSocketChannel setOption(SocketOption<T> name,
 T value)
                                           throws IOException

Description copied from interface: NetworkChannel

Sets the value of a socket option.

Specified by:

setOption in interface NetworkChannel

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

Since:

1.7

See Also:

• StandardSocketOptions

socket

public abstract ServerSocket socket()

Retrieves a server socket associated with this channel.

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

Returns:

A server socket associated with this channel

Throws:

UnsupportedOperationException - If the channel's socket is not an Internet protocol socket

accept

public abstract SocketChannel accept()
                              throws IOException

Accepts a connection made to this channel's socket.

If this channel is in non-blocking mode then this method will immediately return null if there are no pending connections. Otherwise it will block indefinitely until a new connection is available or an I/O error occurs.

The socket channel returned by this method, if any, will be in blocking mode regardless of the blocking mode of this channel.

If bound to an Internet protocol socket address, this method performs exactly the same security checks as the accept method of the ServerSocket class. That is, if a security manager has been installed then for each new connection this method verifies that the address and port number of the connection's remote endpoint are permitted by the security manager's checkAccept method. If bound to a Unix Domain socket address, this method checks NetPermission("accessUnixDomainSocket").

Returns:

The socket channel for the new connection, or null if this channel is in non-blocking mode and no connection is available to be accepted

Throws:

ClosedChannelException - If this channel is closed

AsynchronousCloseException - If another thread closes this channel while the accept operation is in progress

ClosedByInterruptException - If another thread interrupts the current thread while the accept operation is in progress, thereby closing the channel and setting the current thread's interrupt status

NotYetBoundException - If this channel's socket has not yet been bound

SecurityException - If a security manager has been installed and this channel is bound to an InetSocketAddress and the security manager denies access to the remote endpoint of the new connection, or if this channel is bound to a UnixDomainSocketAddress and the security manager denies NetPermission("accessUnixDomainSocket")

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.

Where the channel is bound to a Unix Domain socket address, the socket address is a UnixDomainSocketAddress. If there is a security manager set, its checkPermission method is called with NetPermission ("accessUnixDomainSocket"). If the operation is not allowed an unnamed UnixDomainSocketAddress is returned.

Specified by:

getLocalAddress in interface NetworkChannel

Returns:

The SocketAddress that the socket is bound to, or the SocketAddress representing the loopback address or empty path if denied by the security manager, or null if the channel's socket is not bound

Throws:

ClosedChannelException - If the channel is closed

IOException - If an I/O error occurs