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 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 altogther. 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