Class 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 the open method of this class. It is not possible to create a channel for an arbitrary, pre-existing ServerSocket. 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 support the following options:

Option Name Description
SO_RCVBUF The size of the socket receive buffer
SO_REUSEADDR Re-use address
Additional (implementation specific) options may also be supported.

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

Since:
1.4

Constructors

Modifier Constructor Description
protected ServerSocketChannel​(SelectorProvider provider)

Initializes a new instance of this class.

Methods

Modifier and Type Method Description
abstract SocketChannel accept()

Accepts a connection made to this channel's socket.
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.
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.
int validOps()

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

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

configureBlocking, implCloseChannel, implCloseSelectableChannel, implConfigureBlocking, provider, register

Methods declared in class java.nio.channels.SelectableChannel

blockingLock, isBlocking, isRegistered, keyFor, register

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

begin, close, end

Methods declared in class java.lang.Object

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

Methods declared in interface java.nio.channels.Channel

isOpen

Methods declared in interface java.nio.channels.NetworkChannel

getOption, supportedOptions

Constructors

ServerSocketChannel

protected ServerSocketChannel(SelectorProvider provider)

Initializes a new instance of this class.

Parameters:
provider - The provider that created this channel

Methods

open

public static ServerSocketChannel open()
                                throws IOException

Opens a server-socket channel.

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

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 its checkListen method 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. 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 altogther. If the backlog parameter has the value 0, or a negative value, then an implementation specific default is used.

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
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

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.

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.

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 it does not permit access to the remote endpoint of the new connection
IOException - If some other I/O error occurs

getLocalAddress

public abstract SocketAddress getLocalAddress()
                                       throws IOException

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

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

If there is a security manager set, its checkConnect method is called with the local address and -1 as its arguments to see if the operation is allowed. If the operation is not allowed, a SocketAddress representing the loopback address and the local port of the channel's socket is returned.

Specified by:
getLocalAddress in interface NetworkChannel
Returns:
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
Throws:
ClosedChannelException - If the channel is closed
IOException - If an I/O error occurs

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https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/nio/channels/ServerSocketChannel.html