java/11 : java.base/java/net/SocketImpl.java

SocketImpl
https://openjdk.java.net/
GPLv2 + Classpath Exception
/*
 * Copyright (c) 1995, 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.net;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.FileDescriptor;
import java.util.Set;

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. 
A "plain" socket implements these methods exactly as
described, without attempting to go through a firewall or proxy.
Author:  unascribed
Since:   1.0/**
 * The abstract class {@code SocketImpl} is a common superclass
 * of all classes that actually implement sockets. It is used to
 * create both client and server sockets.
 * <p>
 * A "plain" socket implements these methods exactly as
 * described, without attempting to go through a firewall or proxy.
 *
 * @author  unascribed
 * @since   1.0
 */
public abstract class SocketImpl implements SocketOptions {
    The actual Socket object.
/**
     * The actual Socket object.
     */
    Socket socket = null;
    ServerSocket serverSocket = null;

    The file descriptor object for this socket.
/**
     * The file descriptor object for this socket.
     */
    protected FileDescriptor fd;

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

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

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

    Creates either a stream or a datagram socket.
Params: stream –  if true, create a stream socket; otherwise, create a datagram socket.
Throws: IOException –  if an I/O error occurs while creating the
              socket./**
     * Creates either a stream or a datagram socket.
     *
     * @param      stream   if {@code true}, create a stream socket;
     *                      otherwise, create a datagram socket.
     * @exception  IOException  if an I/O error occurs while creating the
     *               socket.
     */
    protected abstract void create(boolean stream) throws IOException;

    Connects this socket to the specified port on the named host.
Params: 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./**
     * Connects this socket to the specified port on the named host.
     *
     * @param      host   the name of the remote host.
     * @param      port   the port number.
     * @exception  IOException  if an I/O error occurs when connecting to the
     *               remote host.
     */
    protected abstract void connect(String host, int port) throws IOException;

    Connects this socket to the specified port number on the specified host.
Params: address –   the IP address of the remote host.
port –      the port number.
Throws: IOException –  if an I/O error occurs when attempting a
              connection./**
     * Connects this socket to the specified port number on the specified host.
     *
     * @param      address   the IP address of the remote host.
     * @param      port      the port number.
     * @exception  IOException  if an I/O error occurs when attempting a
     *               connection.
     */
    protected abstract void connect(InetAddress address, int port) 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.
Params: 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/**
     * 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.
     *
     * @param      address   the Socket address of the remote host.
     * @param     timeout  the timeout value, in milliseconds, or zero for no timeout.
     * @exception  IOException  if an I/O error occurs when attempting a
     *               connection.
     * @since 1.4
     */
    protected abstract void connect(SocketAddress address, int timeout) throws IOException;

    Binds this socket to the specified local IP address and port number.
Params: 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./**
     * Binds this socket to the specified local IP address and port number.
     *
     * @param      host   an IP address that belongs to a local interface.
     * @param      port   the port number.
     * @exception  IOException  if an I/O error occurs when binding this socket.
     */
    protected abstract void bind(InetAddress host, int port) 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. 
Params: backlog –   the maximum length of the queue.
Throws: IOException –  if an I/O error occurs when creating the queue./**
     * Sets the maximum queue length for incoming connection indications
     * (a request to connect) to the {@code count} argument. If a
     * connection indication arrives when the queue is full, the
     * connection is refused.
     *
     * @param      backlog   the maximum length of the queue.
     * @exception  IOException  if an I/O error occurs when creating the queue.
     */
    protected abstract void listen(int backlog) throws IOException;

    Accepts a connection.
Params: s –   the accepted connection.
Throws: IOException –  if an I/O error occurs when accepting the
              connection./**
     * Accepts a connection.
     *
     * @param      s   the accepted connection.
     * @exception  IOException  if an I/O error occurs when accepting the
     *               connection.
     */
    protected abstract void accept(SocketImpl s) throws IOException;

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

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

    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.
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.
     *
     * @return     the number of bytes that can be read from this socket
     *             without blocking.
     * @exception  IOException  if an I/O error occurs when determining the
     *               number of bytes available.
     */
    protected abstract int available() throws IOException;

    Closes this socket.
Throws: IOException –  if an I/O error occurs when closing this socket./**
     * Closes this socket.
     *
     * @exception  IOException  if an I/O error occurs when closing this socket.
     */
    protected abstract void close() 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.
See Also: Socket.shutdownOutput()
Socket.close()
Socket.setSoLinger(boolean, int)
Since: 1.3/**
     * 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 {@code available} method will return 0, and its
     * {@code read} methods will return {@code -1} (end of stream).
     *
     * @exception IOException if an I/O error occurs when shutting down this
     * socket.
     * @see java.net.Socket#shutdownOutput()
     * @see java.net.Socket#close()
     * @see java.net.Socket#setSoLinger(boolean, int)
     * @since 1.3
     */
    protected void shutdownInput() throws IOException {
      throw new IOException("Method not implemented!");
    }

    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.
See Also: Socket.shutdownInput()
Socket.close()
Socket.setSoLinger(boolean, int)
Since: 1.3/**
     * 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.
     *
     * @exception IOException if an I/O error occurs when shutting down this
     * socket.
     * @see java.net.Socket#shutdownInput()
     * @see java.net.Socket#close()
     * @see java.net.Socket#setSoLinger(boolean, int)
     * @since 1.3
     */
    protected void shutdownOutput() throws IOException {
      throw new IOException("Method not implemented!");
    }

    Returns the value of this socket's fd field. 
See Also: fd
Returns:  the value of this socket's fd field./**
     * Returns the value of this socket's {@code fd} field.
     *
     * @return  the value of this socket's {@code fd} field.
     * @see     java.net.SocketImpl#fd
     */
    protected FileDescriptor getFileDescriptor() {
        return fd;
    }

    Returns the value of this socket's address field. 
See Also: address
Returns:  the value of this socket's address field./**
     * Returns the value of this socket's {@code address} field.
     *
     * @return  the value of this socket's {@code address} field.
     * @see     java.net.SocketImpl#address
     */
    protected InetAddress getInetAddress() {
        return address;
    }

    Returns the value of this socket's port field. 
See Also: port
Returns:  the value of this socket's port field./**
     * Returns the value of this socket's {@code port} field.
     *
     * @return  the value of this socket's {@code port} field.
     * @see     java.net.SocketImpl#port
     */
    protected int getPort() {
        return port;
    }

    Returns whether or not this SocketImpl supports sending
urgent data. By default, false is returned
unless the method is overridden in a sub-class
See Also: address
Returns:  true if urgent data supported
Since: 1.4/**
     * Returns whether or not this SocketImpl supports sending
     * urgent data. By default, false is returned
     * unless the method is overridden in a sub-class
     *
     * @return  true if urgent data supported
     * @see     java.net.SocketImpl#address
     * @since 1.4
     */
    protected boolean supportsUrgentData () {
        return false; // must be overridden in sub-class
    }

    Send one byte of urgent data on the socket.
The byte to be sent is the low eight bits of the parameter
Params: data – The byte of data to send
Throws: IOException – if there is an error
 sending the data.
Since: 1.4/**
     * Send one byte of urgent data on the socket.
     * The byte to be sent is the low eight bits of the parameter
     * @param data The byte of data to send
     * @exception IOException if there is an error
     *  sending the data.
     * @since 1.4
     */
    protected abstract void sendUrgentData (int data) throws IOException;

    Returns the value of this socket's localport field. 
See Also: localport
Returns:  the value of this socket's localport field./**
     * Returns the value of this socket's {@code localport} field.
     *
     * @return  the value of this socket's {@code localport} field.
     * @see     java.net.SocketImpl#localport
     */
    protected int getLocalPort() {
        return localport;
    }

    void setSocket(Socket soc) {
        this.socket = soc;
    }

    Socket getSocket() {
        return socket;
    }

    void setServerSocket(ServerSocket soc) {
        this.serverSocket = soc;
    }

    ServerSocket getServerSocket() {
        return serverSocket;
    }

    Returns the address and port of this socket as a String. 
Returns:  a string representation of this socket./**
     * Returns the address and port of this socket as a {@code String}.
     *
     * @return  a string representation of this socket.
     */
    public String toString() {
        return "Socket[addr=" + getInetAddress() +
            ",port=" + getPort() + ",localport=" + getLocalPort()  + "]";
    }

    void reset() throws IOException {
        address = null;
        port = 0;
        localport = 0;
    }

    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. 
Params: 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/**
     * Sets performance preferences for this socket.
     *
     * <p> 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.
     *
     * <p> 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
     * {@code (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 {@code (0, 1, 2)}.
     *
     * By default, this method does nothing, unless it is overridden in
     * a sub-class.
     *
     * @param  connectionTime
     *         An {@code int} expressing the relative importance of a short
     *         connection time
     *
     * @param  latency
     *         An {@code int} expressing the relative importance of low
     *         latency
     *
     * @param  bandwidth
     *         An {@code int} expressing the relative importance of high
     *         bandwidth
     *
     * @since 1.5
     */
    protected void setPerformancePreferences(int connectionTime,
                                          int latency,
                                          int bandwidth)
    {
        /* Not implemented yet */
    }

    Called to set a socket option.
Params: name – The socket option
value – The value of the socket option. A value of null may be valid for some options.
Type parameters: <T> – The type of the socket option value
Throws: UnsupportedOperationException – if the SocketImpl does not
        support the option
IOException – if an I/O error occurs, or if the socket is closed.
Since: 9/**
     * Called to set a socket option.
     *
     * @param <T> The type of the socket option value
     * @param name The socket option
     *
     * @param value The value of the socket option. A value of {@code null}
     *              may be valid for some options.
     *
     * @throws UnsupportedOperationException if the SocketImpl does not
     *         support the option
     *
     * @throws IOException if an I/O error occurs, or if the socket is closed.
     *
     * @since 9
     */
    protected <T> void setOption(SocketOption<T> name, T value) throws IOException {
        if (name == StandardSocketOptions.SO_KEEPALIVE &&
                (getSocket() != null)) {
            setOption(SocketOptions.SO_KEEPALIVE, value);
        } else if (name == StandardSocketOptions.SO_SNDBUF &&
                (getSocket() != null)) {
            setOption(SocketOptions.SO_SNDBUF, value);
        } else if (name == StandardSocketOptions.SO_RCVBUF) {
            setOption(SocketOptions.SO_RCVBUF, value);
        } else if (name == StandardSocketOptions.SO_REUSEADDR) {
            setOption(SocketOptions.SO_REUSEADDR, value);
        } else if (name == StandardSocketOptions.SO_REUSEPORT &&
            supportedOptions().contains(name)) {
            setOption(SocketOptions.SO_REUSEPORT, value);
        } else if (name == StandardSocketOptions.SO_LINGER &&
                (getSocket() != null)) {
            setOption(SocketOptions.SO_LINGER, value);
        } else if (name == StandardSocketOptions.IP_TOS) {
            setOption(SocketOptions.IP_TOS, value);
        } else if (name == StandardSocketOptions.TCP_NODELAY &&
                (getSocket() != null)) {
            setOption(SocketOptions.TCP_NODELAY, value);
        } else {
            throw new UnsupportedOperationException("unsupported option");
        }
    }

    Called to get a socket option.
Params: name – The socket option
Type parameters: <T> – The type of the socket option value
Throws: UnsupportedOperationException – if the SocketImpl does not
        support the option.
IOException – if an I/O error occurs, or if the socket is closed.
Returns: the value of the named option
Since: 9/**
     * Called to get a socket option.
     *
     * @param <T> The type of the socket option value
     * @param name The socket option
     *
     * @return the value of the named option
     *
     * @throws UnsupportedOperationException if the SocketImpl does not
     *         support the option.
     *
     * @throws IOException if an I/O error occurs, or if the socket is closed.
     *
     * @since 9
     */
    @SuppressWarnings("unchecked")
    protected <T> T getOption(SocketOption<T> name) throws IOException {
        if (name == StandardSocketOptions.SO_KEEPALIVE &&
                (getSocket() != null)) {
            return (T)getOption(SocketOptions.SO_KEEPALIVE);
        } else if (name == StandardSocketOptions.SO_SNDBUF &&
                (getSocket() != null)) {
            return (T)getOption(SocketOptions.SO_SNDBUF);
        } else if (name == StandardSocketOptions.SO_RCVBUF) {
            return (T)getOption(SocketOptions.SO_RCVBUF);
        } else if (name == StandardSocketOptions.SO_REUSEADDR) {
            return (T)getOption(SocketOptions.SO_REUSEADDR);
        } else if (name == StandardSocketOptions.SO_REUSEPORT &&
            supportedOptions().contains(name)) {
            return (T)getOption(SocketOptions.SO_REUSEPORT);
        } else if (name == StandardSocketOptions.SO_LINGER &&
                (getSocket() != null)) {
            return (T)getOption(SocketOptions.SO_LINGER);
        } else if (name == StandardSocketOptions.IP_TOS) {
            return (T)getOption(SocketOptions.IP_TOS);
        } else if (name == StandardSocketOptions.TCP_NODELAY &&
                (getSocket() != null)) {
            return (T)getOption(SocketOptions.TCP_NODELAY);
        } else {
            throw new UnsupportedOperationException("unsupported option");
        }
    }

    private static final Set<SocketOption<?>> socketOptions;

    private static final Set<SocketOption<?>> serverSocketOptions;

    static {
        socketOptions = Set.of(StandardSocketOptions.SO_KEEPALIVE,
                               StandardSocketOptions.SO_SNDBUF,
                               StandardSocketOptions.SO_RCVBUF,
                               StandardSocketOptions.SO_REUSEADDR,
                               StandardSocketOptions.SO_LINGER,
                               StandardSocketOptions.IP_TOS,
                               StandardSocketOptions.TCP_NODELAY);

        serverSocketOptions = Set.of(StandardSocketOptions.SO_RCVBUF,
                                     StandardSocketOptions.SO_REUSEADDR,
                                     StandardSocketOptions.IP_TOS);
    }

    Returns a set of SocketOptions supported by this impl
and by this impl's socket (Socket or ServerSocket)
Returns: a Set of SocketOptions
Since: 9/**
     * Returns a set of SocketOptions supported by this impl
     * and by this impl's socket (Socket or ServerSocket)
     *
     * @return a Set of SocketOptions
     *
     * @since 9
     */
    protected Set<SocketOption<?>> supportedOptions() {
        if (getSocket() != null) {
            return socketOptions;
        } else {
            return serverSocketOptions;
        }
    }
}
Params:	stream – if `true`, create a stream socket; otherwise, create a datagram socket.
Throws:	IOException – if an I/O error occurs while creating the socket.
Params:	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.
Params:	address – the IP address of the remote host. port – the port number.
Throws:	IOException – if an I/O error occurs when attempting a connection.
Params:	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
Params:	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.
Params:	backlog – the maximum length of the queue.
Throws:	IOException – if an I/O error occurs when creating the queue.
Params:	s – the accepted connection.
Throws:	IOException – if an I/O error occurs when accepting the connection.
Throws:	IOException – if an I/O error occurs when creating the input stream.
Returns:	a stream for reading from this socket.
Throws:	IOException – if an I/O error occurs when shutting down this socket.
See Also:	Socket.shutdownOutput() Socket.close() Socket.setSoLinger(boolean, int)
Since:	1.3
See Also:	address
Returns:	the value of this socket's `address` field.
See Also:	port
Returns:	the value of this socket's `port` field.
Params:	data – The byte of data to send
Throws:	IOException – if there is an error sending the data.
Since:	1.4
See Also:	localport
Returns:	the value of this socket's `localport` field.
Params:	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
Params:	name – The socket option value – The value of the socket option. A value of `null` may be valid for some options.
Type parameters:	<T> – The type of the socket option value
Throws:	UnsupportedOperationException – if the SocketImpl does not support the option IOException – if an I/O error occurs, or if the socket is closed.
Since:	9
Params:	name – The socket option
Type parameters:	<T> – The type of the socket option value
Throws:	UnsupportedOperationException – if the SocketImpl does not support the option. IOException – if an I/O error occurs, or if the socket is closed.
Returns:	the value of the named option
Since:	9
/

java/ 11/ java.base/java/net/SocketImpl.java
