Module java.base
Package java.net

Class SocketImpl

java.lang.Object
java.net.SocketImpl
All Implemented Interfaces:
SocketOptions
public abstract class SocketImpl
extends Object
implements SocketOptions
The abstract class SocketImpl is a common superclass of all classes that actually implement sockets. It is used to create both client and server sockets.
Implementation Note:
Client and server sockets created with the Socket and SocketServer public constructors create a system-default SocketImpl. The JDK historically used a SocketImpl implementation type named "PlainSocketImpl" that has since been replaced by a newer implementation. The JDK continues to ship with the older implementation to allow code to run that depends on unspecified behavior that differs between the old and new implementations. The old implementation will be used if the Java virtual machine is started with the system property jdk.net.usePlainSocketImpl set to use the old implementation. It may also be set in the JDK's network configuration file, located in ${java.home}/conf/net.properties. The value of the property is the string representation of a boolean. If set without a value then it defaults to true, hence running with -Djdk.net.usePlainSocketImpl or -Djdk.net.usePlainSocketImpl=true will configure the Java virtual machine to use the old implementation. The property and old implementation will be removed in a future version.
Since:
1.0

  • Field Details

    • fd

      protected FileDescriptor fd
      The file descriptor object for this socket.

    • address

      protected InetAddress address
      The IP address of the remote end of this socket.

    • port

      protected int port
      The port number on the remote host to which this socket is connected.

    • localport

      protected int localport
      The local port number to which this socket is connected.

  • Constructor Details

    • SocketImpl

      public SocketImpl()
      Initialize a new instance of this class

  • Method Details

    • create

      protected abstract void create​(boolean stream) throws IOException
      Creates either a stream or a datagram socket.
      Parameters:
      stream - if true, create a stream socket; otherwise, create a datagram socket.
      Throws:
      IOException - if an I/O error occurs while creating the socket.

    • connect

      protected abstract void connect​(String host, int port) throws IOException
      Connects this socket to the specified port on the named host.
      Parameters:
      host - the name of the remote host.
      port - the port number.
      Throws:
      IOException - if an I/O error occurs when connecting to the remote host.

    • connect

      protected abstract void connect​(InetAddress address, int port) throws IOException
      Connects this socket to the specified port number on the specified host.
      Parameters:
      address - the IP address of the remote host.
      port - the port number.
      Throws:
      IOException - if an I/O error occurs when attempting a connection.

    • connect

      protected abstract void connect​(SocketAddress address, int timeout) throws IOException
      Connects this socket to the specified port number on the specified host. A timeout of zero is interpreted as an infinite timeout. The connection will then block until established or an error occurs.
      Parameters:
      address - the Socket address of the remote host.
      timeout - the timeout value, in milliseconds, or zero for no timeout.
      Throws:
      IOException - if an I/O error occurs when attempting a connection.
      Since:
      1.4

    • bind

      protected abstract void bind​(InetAddress host, int port) throws IOException
      Binds this socket to the specified local IP address and port number.
      Parameters:
      host - an IP address that belongs to a local interface.
      port - the port number.
      Throws:
      IOException - if an I/O error occurs when binding this socket.

    • listen

      protected abstract void listen​(int backlog) throws IOException
      Sets the maximum queue length for incoming connection indications (a request to connect) to the count argument. If a connection indication arrives when the queue is full, the connection is refused.
      Parameters:
      backlog - the maximum length of the queue.
      Throws:
      IOException - if an I/O error occurs when creating the queue.

    • accept

      protected abstract void accept​(SocketImpl s) throws IOException
      Accepts a connection.
      Parameters:
      s - the accepted connection.
      Throws:
      IOException - if an I/O error occurs when accepting the connection.

    • getInputStream

      protected abstract InputStream getInputStream() throws IOException
      Returns an input stream for this socket.
      Returns:
      a stream for reading from this socket.
      Throws:
      IOException - if an I/O error occurs when creating the input stream.

    • getOutputStream

      protected abstract OutputStream getOutputStream() throws IOException
      Returns an output stream for this socket.
      Returns:
      an output stream for writing to this socket.
      Throws:
      IOException - if an I/O error occurs when creating the output stream.

    • available

      protected abstract int available() throws IOException
      Returns the number of bytes that can be read from this socket without blocking.
      Returns:
      the number of bytes that can be read from this socket without blocking.
      Throws:
      IOException - if an I/O error occurs when determining the number of bytes available.

    • close

      protected abstract void close() throws IOException
      Closes this socket.
      Throws:
      IOException - if an I/O error occurs when closing this socket.

    • shutdownInput

      protected void shutdownInput() throws IOException
      Places the input stream for this socket at "end of stream". Any data sent to this socket is acknowledged and then silently discarded. If you read from a socket input stream after invoking this method on the socket, the stream's available method will return 0, and its read methods will return -1 (end of stream).
      Throws:
      IOException - if an I/O error occurs when shutting down this socket.
      Since:
      1.3
      See Also:
      Socket.shutdownOutput(), Socket.close(), Socket.setSoLinger(boolean, int)

    • shutdownOutput

      protected void shutdownOutput() throws IOException
      Disables the output stream for this socket. For a TCP socket, any previously written data will be sent followed by TCP's normal connection termination sequence. If you write to a socket output stream after invoking shutdownOutput() on the socket, the stream will throw an IOException.
      Throws:
      IOException - if an I/O error occurs when shutting down this socket.
      Since:
      1.3
      See Also:
      Socket.shutdownInput(), Socket.close(), Socket.setSoLinger(boolean, int)

    • getFileDescriptor

      protected FileDescriptor getFileDescriptor()
      Returns the value of this socket's fd field.
      Returns:
      the value of this socket's fd field.
      See Also:
      fd

    • getInetAddress

      protected InetAddress getInetAddress()
      Returns the value of this socket's address field.
      Returns:
      the value of this socket's address field.
      See Also:
      address

    • getPort

      protected int getPort()
      Returns the value of this socket's port field.
      Returns:
      the value of this socket's port field.
      See Also:
      port

    • supportsUrgentData

      protected boolean supportsUrgentData()
      Returns whether or not this SocketImpl supports sending urgent data. By default, false is returned unless the method is overridden in a sub-class
      Returns:
      true if urgent data supported
      Since:
      1.4
      See Also:
      address

    • sendUrgentData

      protected abstract void sendUrgentData​(int data) throws IOException
      Send one byte of urgent data on the socket. The byte to be sent is the low eight bits of the parameter
      Parameters:
      data - The byte of data to send
      Throws:
      IOException - if there is an error sending the data.
      Since:
      1.4

    • getLocalPort

      protected int getLocalPort()
      Returns the value of this socket's localport field.
      Returns:
      the value of this socket's localport field.
      See Also:
      localport

    • toString

      public String toString()
      Returns the address and port of this socket as a String.
      Overrides:
      toString in class Object
      Returns:
      a string representation of this socket.

    • setPerformancePreferences

      protected void setPerformancePreferences​(int connectionTime, int latency, int bandwidth)
      Sets performance preferences for this socket.

      Sockets use the TCP/IP protocol by default. Some implementations may offer alternative protocols which have different performance characteristics than TCP/IP. This method allows the application to express its own preferences as to how these tradeoffs should be made when the implementation chooses from the available protocols.

      Performance preferences are described by three integers whose values indicate the relative importance of short connection time, low latency, and high bandwidth. The absolute values of the integers are irrelevant; in order to choose a protocol the values are simply compared, with larger values indicating stronger preferences. Negative values represent a lower priority than positive values. If the application prefers short connection time over both low latency and high bandwidth, for example, then it could invoke this method with the values (1, 0, 0). If the application prefers high bandwidth above low latency, and low latency above short connection time, then it could invoke this method with the values (0, 1, 2). By default, this method does nothing, unless it is overridden in a sub-class.

      Parameters:
      connectionTime - An int expressing the relative importance of a short connection time
      latency - An int expressing the relative importance of low latency
      bandwidth - An int expressing the relative importance of high bandwidth
      Since:
      1.5

    • setOption

      protected <T> void setOption​(SocketOption<T> name, T value) throws IOException
      Called to set a socket option.
      Implementation Requirements:
      The default implementation of this method first checks that the given socket option name is not null, then throws UnsupportedOperationException. Subclasses should override this method with an appropriate implementation.
      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 valid for some options.
      Throws:
      UnsupportedOperationException - if the SocketImpl does not support the option
      IllegalArgumentException - if the value is not valid for the option
      IOException - if an I/O error occurs, or if the socket is closed
      NullPointerException - if name is null
      Since:
      9

    • getOption

      protected <T> T getOption​(SocketOption<T> name) throws IOException
      Called to get a socket option.
      Implementation Requirements:
      The default implementation of this method first checks that the given socket option name is not null, then throws UnsupportedOperationException. Subclasses should override this method with an appropriate implementation.
      Type Parameters:
      T - The type of the socket option value
      Parameters:
      name - The socket option
      Returns:
      the value of the named option
      Throws:
      UnsupportedOperationException - if the SocketImpl does not support the option
      IOException - if an I/O error occurs, or if the socket is closed
      NullPointerException - if name is null
      Since:
      9

    • supportedOptions

      protected Set<SocketOption<?>> supportedOptions()
      Returns a set of SocketOptions supported by this impl and by this impl's socket (Socket or ServerSocket)
      Implementation Requirements:
      The default implementation of this method returns an empty set. Subclasses should override this method with an appropriate implementation.
      Returns:
      a Set of SocketOptions
      Since:
      9