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package java.nio.channels;

import java.io.IOException;
import java.net.NetPermission;
import java.net.ProtocolFamily;
import java.net.ServerSocket;
import java.net.SocketOption;
import java.net.SocketAddress;
import java.net.UnixDomainSocketAddress;
import java.nio.channels.spi.AbstractSelectableChannel;
import java.nio.channels.spi.SelectorProvider;
import static java.util.Objects.requireNonNull;

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.

Author:
Mark Reinhold, JSR-51 Expert Group
Since:
1.4/**
 * A selectable channel for stream-oriented listening sockets.
 *
 * <p> A server-socket channel is created by invoking one of the {@code open}
 * methods of this class. The no-arg {@link #open() open} method opens a server-socket
 * channel for an <i>Internet protocol</i> socket. The {@link #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 {@link #accept() accept} method of an
 * unbound server-socket channel will cause a {@link NotYetBoundException}
 * to be thrown. A server-socket channel can be bound by invoking one of the
 * {@link #bind(java.net.SocketAddress, int) bind} methods defined by this class.
 *
 * <p> Socket options are configured using the {@link #setOption(SocketOption,Object)
 * setOption} method. Server-socket channels for <i>Internet protocol</i> sockets
 * support the following options:
 * <blockquote>
 * <table class="striped">
 * <caption style="display:none">Socket options</caption>
 * <thead>
 *   <tr>
 *     <th scope="col">Option Name</th>
 *     <th scope="col">Description</th>
 *   </tr>
 * </thead>
 * <tbody>
 *   <tr>
 *     <th scope="row"> {@link java.net.StandardSocketOptions#SO_RCVBUF SO_RCVBUF} </th>
 *     <td> The size of the socket receive buffer </td>
 *   </tr>
 *   <tr>
 *     <th scope="row"> {@link java.net.StandardSocketOptions#SO_REUSEADDR SO_REUSEADDR} </th>
 *     <td> Re-use address </td>
 *   </tr>
 * </tbody>
 * </table>
 * </blockquote>
 *
 * <p> Server-socket channels for <i>Unix domain</i> sockets support:
 * <blockquote>
 * <table class="striped">
 * <caption style="display:none">Socket options</caption>
 * <thead>
 *   <tr>
 *     <th scope="col">Option Name</th>
 *     <th scope="col">Description</th>
 *   </tr>
 * </thead>
 * <tbody>
 *   <tr>
 *     <th scope="row"> {@link java.net.StandardSocketOptions#SO_RCVBUF SO_RCVBUF} </th>
 *     <td> The size of the socket receive buffer </td>
 *   </tr>
 * </tbody>
 * </table>
 * </blockquote>
 *
 * <p> Additional (implementation specific) options may also be supported.
 *
 * <p> Server-socket channels are safe for use by multiple concurrent threads.
 * </p>
 *
 * @author Mark Reinhold
 * @author JSR-51 Expert Group
 * @since 1.4
 */

public abstract class ServerSocketChannel
    extends AbstractSelectableChannel
    implements NetworkChannel
{

    
Initializes a new instance of this class.
Params:
provider – 
        The provider that created this channel/**
     * Initializes a new instance of this class.
     *
     * @param  provider
     *         The provider that created this channel
     */
    protected ServerSocketChannel(SelectorProvider provider) {
        super(provider);
    }

    
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. 
Throws:
IOException – 
         If an I/O error occurs
See Also:
    
     *          java.net.preferIPv4Stack system property
Returns:
 A new socket channel/**
     * Opens a server-socket channel for an <i>Internet protocol</i> socket.
     *
     * <p> The new channel is created by invoking the {@link
     * java.nio.channels.spi.SelectorProvider#openServerSocketChannel
     * openServerSocketChannel} method of the system-wide default {@link
     * java.nio.channels.spi.SelectorProvider} object.
     *
     * <p> The new channel's socket is initially unbound; it must be bound to a
     * specific address via one of its socket's {@link
     * java.net.ServerSocket#bind(SocketAddress) bind} methods before
     * connections can be accepted.  </p>
     *
     * @return  A new socket channel
     *
     * @throws  IOException
     *          If an I/O error occurs
     *
     * @see     <a href="../../net/doc-files/net-properties.html#Ipv4IPv6">
     *          java.net.preferIPv4Stack</a> system property
     */
    public static ServerSocketChannel open() throws IOException {
        return SelectorProvider.provider().openServerSocketChannel();
    }

    
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. 
Params:
family – 
         The protocol family
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
See Also:
    
     *          java.net.preferIPv4Stack system property
Returns:
 A new socket channel
Since:
15/**
     * Opens a server-socket channel. The {@code family} parameter specifies the
     * {@link ProtocolFamily protocol family} of the channel's socket.
     *
     * <p> The new channel is created by invoking the {@link
     * java.nio.channels.spi.SelectorProvider#openServerSocketChannel(ProtocolFamily)
     * openServerSocketChannel(ProtocolFamily)} method of the system-wide default {@link
     * java.nio.channels.spi.SelectorProvider} object. </p>
     *
     * @param   family
     *          The protocol family
     *
     * @return  A new socket channel
     *
     * @throws  UnsupportedOperationException
     *          If the specified protocol family is not supported. For example,
     *          suppose the parameter is specified as {@link
     *          java.net.StandardProtocolFamily#INET6 StandardProtocolFamily.INET6}
     *          but IPv6 is not enabled on the platform.
     * @throws  IOException
     *          If an I/O error occurs
     *
     * @see     <a href="../../net/doc-files/net-properties.html#Ipv4IPv6">
     *          java.net.preferIPv4Stack</a> system property
     *
     * @since 15
     */
    public static ServerSocketChannel open(ProtocolFamily family) throws IOException {
        return SelectorProvider.provider().openServerSocketChannel(requireNonNull(family));
    }

    
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. 
Returns:
 The valid-operation set/**
     * Returns an operation set identifying this channel's supported
     * operations.
     *
     * <p> Server-socket channels only support the accepting of new
     * connections, so this method returns {@link SelectionKey#OP_ACCEPT}.
     * </p>
     *
     * @return  The valid-operation set
     */
    public final int validOps() {
        return SelectionKey.OP_ACCEPT;
    }


    // -- ServerSocket-specific operations --

    
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);

Params:
local –  The local address to bind the socket, or null to bind to an automatically assigned socket address
Throws:
AlreadyBoundException –               {@inheritDoc}
UnsupportedAddressTypeException –     {@inheritDoc}
ClosedChannelException –              {@inheritDoc}
IOException –                         {@inheritDoc}
SecurityException – 
         If a security manager has been installed and it denies the
         operation
Returns:
 This channel
Since:
1.7/**
     * Binds the channel's socket to a local address and configures the socket
     * to listen for connections.
     *
     * <p> An invocation of this method is equivalent to the following:
     * <blockquote><pre>
     * bind(local, 0);
     * </pre></blockquote>
     *
     * @param   local
     *          The local address to bind the socket, or {@code null} to bind
     *          to an automatically assigned socket address
     *
     * @return  This channel
     *
     * @throws  AlreadyBoundException               {@inheritDoc}
     * @throws  UnsupportedAddressTypeException     {@inheritDoc}
     * @throws  ClosedChannelException              {@inheritDoc}
     * @throws  IOException                         {@inheritDoc}
     * @throws  SecurityException
     *          If a security manager has been installed and it denies the
     *          operation
     *
     * @since 1.7
     */
    public final ServerSocketChannel bind(SocketAddress local)
        throws IOException
    {
        return bind(local, 0);
    }

    
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 altogther. If the backlog parameter has the value 0, or a negative value, then an implementation specific default is used. 
Params:
local –  The address to bind the socket, or null to bind to an automatically assigned socket address
backlog – 
         The maximum number of pending connections
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 "accessUnixDomainSocket").
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.
Returns:
 This channel
Since:
1.7/**
     * Binds the channel's socket to a local address and configures the socket to
     * listen for connections.
     *
     * <p> This method is used to establish an association between the socket and
     * a local address. For <i>Internet protocol</i> sockets, once an association
     * is established then the socket remains bound until the channel is closed.
     *
     * <p> The {@code 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 {@code backlog} parameter has
     * the value {@code 0}, or a negative value, then an implementation specific
     * default is used.
     *
     * @apiNote
     * Binding a server socket channel for a <i>Unix Domain</i> socket, creates a
     * file corresponding to the file path in the {@link 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 {@code null} address
     * causes the socket to be <i>automatically</i> 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.
     *
     * @implNote
     * Each platform enforces an implementation specific, maximum length for the
     * name of a <i>Unix Domain</i> 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 <i>automatically</i>
     * bound server socket channels. See the <i>Unix domain</i>
     * <a href="../../net/doc-files/net-properties.html#Unixdomain">networking
     * properties</a> that can be used to select the temporary directory where
     * these sockets are created.
     *
     * @param   local
     *          The address to bind the socket, or {@code null} to bind to
     *          an automatically assigned socket address
     * @param   backlog
     *          The maximum number of pending connections
     *
     * @return  This channel
     *
     * @throws  AlreadyBoundException
     *          If the socket is already bound
     * @throws  UnsupportedAddressTypeException
     *          If the type of the given address is not supported
     * @throws  ClosedChannelException
     *          If this channel is closed
     * @throws  IOException
     *          If some other I/O error occurs
     * @throws  SecurityException
     *          If a security manager has been installed and its {@link
     *          SecurityManager#checkListen checkListen} method denies
     *          the operation for an <i>Internet protocol</i> socket address,
     *          or for a <i>Unix domain</i> socket address if it denies
     *          {@link NetPermission}{@code("accessUnixDomainSocket")}.
     *
     * @since 1.7
     */
    public abstract ServerSocketChannel bind(SocketAddress local, int backlog)
        throws IOException;

    
Throws:
UnsupportedOperationException –           {@inheritDoc}
IllegalArgumentException –                {@inheritDoc}
ClosedChannelException –                  {@inheritDoc}
IOException –                             {@inheritDoc}
Since:
1.7/**
     * @throws  UnsupportedOperationException           {@inheritDoc}
     * @throws  IllegalArgumentException                {@inheritDoc}
     * @throws  ClosedChannelException                  {@inheritDoc}
     * @throws  IOException                             {@inheritDoc}
     *
     * @since 1.7
     */
    public abstract <T> ServerSocketChannel setOption(SocketOption<T> name, T value)
        throws IOException;

    
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. 
Throws:
UnsupportedOperationException – 
         If the channel's socket is not an Internet protocol socket
Returns:
 A server socket associated with this channel/**
     * Retrieves a server socket associated with this channel.
     *
     * <p> The returned object will not declare any public methods that are not
     * declared in the {@link java.net.ServerSocket} class.  </p>
     *
     * @return  A server socket associated with this channel
     *
     * @throws  UnsupportedOperationException
     *          If the channel's socket is not an <i>Internet protocol</i> socket
     */
    public abstract ServerSocket socket();

    
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"). 
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
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/**
     * Accepts a connection made to this channel's socket.
     *
     * <p> If this channel is in non-blocking mode then this method will
     * immediately return {@code null} if there are no pending connections.
     * Otherwise it will block indefinitely until a new connection is available
     * or an I/O error occurs.
     *
     * <p> The socket channel returned by this method, if any, will be in
     * blocking mode regardless of the blocking mode of this channel.
     *
     * <p> If bound to an <i>Internet protocol</i> socket address, this method
     * performs exactly the same security checks as the {@link
     * java.net.ServerSocket#accept accept} method of the {@link java.net.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 {@link java.lang.SecurityManager#checkAccept checkAccept}
     * method. If bound to a <i>Unix Domain</i> socket address, this method checks
     * {@link NetPermission}{@code ("accessUnixDomainSocket")}.
     *
     * @return  The socket channel for the new connection,
     *          or {@code null} if this channel is in non-blocking mode
     *          and no connection is available to be accepted
     *
     * @throws  ClosedChannelException
     *          If this channel is closed
     *
     * @throws  AsynchronousCloseException
     *          If another thread closes this channel
     *          while the accept operation is in progress
     *
     * @throws  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
     *
     * @throws  NotYetBoundException
     *          If this channel's socket has not yet been bound
     *
     * @throws  SecurityException
     *          If a security manager has been installed and this
     *          channel is bound to an {@link InetSocketAddress}
     *          and the security manager denies access to the remote endpoint
     *          of the new connection, or if this channel is bound to a
     *          {@link UnixDomainSocketAddress} and the security manager
     *          denies {@link NetPermission}{@code ("accessUnixDomainSocket")}
     *
     * @throws  IOException
     *          If some other I/O error occurs
     */
    public abstract SocketChannel accept() throws IOException;

    
{@inheritDoc} 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. 
Throws:
ClosedChannelException –     {@inheritDoc}
IOException –                {@inheritDoc}
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/**
     * {@inheritDoc}
     *
     * If there is a security manager set, its {@code checkConnect} method is
     * called with the local address and {@code -1} as its arguments to see
     * if the operation is allowed. If the operation is not allowed,
     * a {@code SocketAddress} representing the
     * {@link java.net.InetAddress#getLoopbackAddress loopback} address and the
     * local port of the channel's socket is returned.
     *
     * <p> Where the channel is bound to a <i>Unix Domain</i> socket address, the socket
     * address is a {@link UnixDomainSocketAddress}. If there is a security manager
     * set, its {@link SecurityManager#checkPermission(java.security.Permission)
     * checkPermission} method is called with {@link NetPermission}{@code
     * ("accessUnixDomainSocket")}. If the operation is not allowed an unnamed
     * {@link UnixDomainSocketAddress} is returned.
     *
     * @return  The {@code SocketAddress} that the socket is bound to, or the
     *          {@code SocketAddress} representing the loopback address or empty
     *          path if denied by the security manager, or {@code null} if the
     *          channel's socket is not bound
     *
     * @throws  ClosedChannelException     {@inheritDoc}
     * @throws  IOException                {@inheritDoc}
     */
    @Override
    public abstract SocketAddress getLocalAddress() throws IOException;
}