ServerSocketChannel (Java Platform SE 8 )
Keywords: java.nio.channels.ServerSocketChannel class
Date: 2026-04-22

compact1, compact2, compact3
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 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

- - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `ServerSocketChannel(SelectorProvider provider)` Initializes a new instance of this class.

  - ### Method Summary

    All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and 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 inherited from class java.nio.channels.spi.AbstractSelectableChannel

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

    - ### Methods inherited from class java.nio.channels.SelectableChannel

      `register`

    - ### Methods inherited from class java.nio.channels.spi.AbstractInterruptibleChannel

      `begin, close, end, isOpen`

    - ### Methods inherited from class java.lang.Object

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

    - ### Methods inherited from interface java.nio.channels.NetworkChannel

      `getOption, supportedOptions`

    - ### Methods inherited from interface java.nio.channels.Channel

      `close, isOpen`

- - ### Constructor Detail

    - #### ServerSocketChannel

          protected ServerSocketChannel(SelectorProvider provider)

      Initializes a new instance of this class.
      Parameters:
        `provider` - The provider that created this channel

  - ### Method Detail

    - #### 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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