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/*
 * Copyright 2001-2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.net;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.SocketException;

/**
 * The SocketClient provides the basic operations that are required of
 * client objects accessing sockets.  It is meant to be
 * subclassed to avoid having to rewrite the same code over and over again
 * to open a socket, close a socket, set timeouts, etc.  Of special note
 * is the  setSocketFactory 
 * method, which allows you to control the type of Socket the SocketClient
 * creates for initiating network connections.  This is especially useful
 * for adding SSL or proxy support as well as better support for applets.  For
 * example, you could create a
 *  SocketFactory  that
 * requests browser security capabilities before creating a socket.
 * All classes derived from SocketClient should use the
 *  _socketFactory_  member variable to
 * create Socket and ServerSocket instances rather than instanting
 * them by directly invoking a constructor.  By honoring this contract
 * you guarantee that a user will always be able to provide his own
 * Socket implementations by substituting his own SocketFactory.
 * @author Daniel F. Savarese
 * @see SocketFactory
 */
public abstract class SocketClient
{
    /**
     * The end of line character sequence used by most IETF protocols.  That
     * is a carriage return followed by a newline: "\r\n"
     */
    public static final String NETASCII_EOL = "\r\n";

    /** The default SocketFactory shared by all SocketClient instances. */
    private static final SocketFactory __DEFAULT_SOCKET_FACTORY =
        new DefaultSocketFactory();

    /** The timeout to use after opening a socket. */
    protected int _timeout_;

    /** The socket used for the connection. */
    protected Socket _socket_;

    /**
     * A status variable indicating if the client's socket is currently open.
     */
    protected boolean _isConnected_;

    /** The default port the client should connect to. */
    protected int _defaultPort_;

    /** The socket's InputStream. */
    protected InputStream _input_;

    /** The socket's OutputStream. */
    protected OutputStream _output_;

    /** The socket's SocketFactory. */
    protected SocketFactory _socketFactory_;


    /**
     * Default constructor for SocketClient.  Initializes
     * _socket_ to null, _timeout_ to 0, _defaultPort to 0,
     * _isConnected_ to false, and _socketFactory_ to a shared instance of
     * DefaultSocketFactory .
     */
    public SocketClient()
    {
        _socket_ = null;
        _input_ = null;
        _output_ = null;
        _timeout_ = 0;
        _defaultPort_ = 0;
        _isConnected_ = false;
        _socketFactory_ = __DEFAULT_SOCKET_FACTORY;
    }


    /**
     * Because there are so many connect() methods, the _connectAction_()
     * method is provided as a means of performing some action immediately
     * after establishing a connection, rather than reimplementing all
     * of the connect() methods.  The last action performed by every
     * connect() method after opening a socket is to call this method.
     * 

* This method sets the timeout on the just opened socket to the default * timeout set by setDefaultTimeout() , * sets _input_ and _output_ to the socket's InputStream and OutputStream * respectively, and sets _isConnected_ to true. *

* Subclasses overriding this method should start by calling * super._connectAction_() first to ensure the * initialization of the aforementioned protected variables. */ protected void _connectAction_() throws IOException { _socket_.setSoTimeout(_timeout_); _input_ = _socket_.getInputStream(); _output_ = _socket_.getOutputStream(); _isConnected_ = true; } /** * Opens a Socket connected to a remote host at the specified port and * originating from the current host at a system assigned port. * Before returning, _connectAction_() * is called to perform connection initialization actions. *

* @param host The remote host. * @param port The port to connect to on the remote host. * @exception SocketException If the socket timeout could not be set. * @exception IOException If the socket could not be opened. In most * cases you will only want to catch IOException since SocketException is * derived from it. */ public void connect(InetAddress host, int port) throws SocketException, IOException { _socket_ = _socketFactory_.createSocket(host, port); _connectAction_(); } /** * Opens a Socket connected to a remote host at the specified port and * originating from the current host at a system assigned port. * Before returning, _connectAction_() * is called to perform connection initialization actions. *

* @param hostname The name of the remote host. * @param port The port to connect to on the remote host. * @exception SocketException If the socket timeout could not be set. * @exception IOException If the socket could not be opened. In most * cases you will only want to catch IOException since SocketException is * derived from it. * @exception UnknownHostException If the hostname cannot be resolved. */ public void connect(String hostname, int port) throws SocketException, IOException { _socket_ = _socketFactory_.createSocket(hostname, port); _connectAction_(); } /** * Opens a Socket connected to a remote host at the specified port and * originating from the specified local address and port. * Before returning, _connectAction_() * is called to perform connection initialization actions. *

* @param host The remote host. * @param port The port to connect to on the remote host. * @param localAddr The local address to use. * @param localPort The local port to use. * @exception SocketException If the socket timeout could not be set. * @exception IOException If the socket could not be opened. In most * cases you will only want to catch IOException since SocketException is * derived from it. */ public void connect(InetAddress host, int port, InetAddress localAddr, int localPort) throws SocketException, IOException { _socket_ = _socketFactory_.createSocket(host, port, localAddr, localPort); _connectAction_(); } /** * Opens a Socket connected to a remote host at the specified port and * originating from the specified local address and port. * Before returning, _connectAction_() * is called to perform connection initialization actions. *

* @param hostname The name of the remote host. * @param port The port to connect to on the remote host. * @param localAddr The local address to use. * @param localPort The local port to use. * @exception SocketException If the socket timeout could not be set. * @exception IOException If the socket could not be opened. In most * cases you will only want to catch IOException since SocketException is * derived from it. * @exception UnknownHostException If the hostname cannot be resolved. */ public void connect(String hostname, int port, InetAddress localAddr, int localPort) throws SocketException, IOException { _socket_ = _socketFactory_.createSocket(hostname, port, localAddr, localPort); _connectAction_(); } /** * Opens a Socket connected to a remote host at the current default port * and originating from the current host at a system assigned port. * Before returning, _connectAction_() * is called to perform connection initialization actions. *

* @param host The remote host. * @exception SocketException If the socket timeout could not be set. * @exception IOException If the socket could not be opened. In most * cases you will only want to catch IOException since SocketException is * derived from it. */ public void connect(InetAddress host) throws SocketException, IOException { connect(host, _defaultPort_); } /** * Opens a Socket connected to a remote host at the current default * port and originating from the current host at a system assigned port. * Before returning, _connectAction_() * is called to perform connection initialization actions. *

* @param hostname The name of the remote host. * @exception SocketException If the socket timeout could not be set. * @exception IOException If the socket could not be opened. In most * cases you will only want to catch IOException since SocketException is * derived from it. * @exception UnknownHostException If the hostname cannot be resolved. */ public void connect(String hostname) throws SocketException, IOException { connect(hostname, _defaultPort_); } /** * Disconnects the socket connection. * You should call this method after you've finished using the class * instance and also before you call * connect() * again. _isConnected_ is set to false, _socket_ is set to null, * _input_ is set to null, and _output_ is set to null. *

* @exception IOException If there is an error closing the socket. */ public void disconnect() throws IOException { _socket_.close(); _input_.close(); _output_.close(); _socket_ = null; _input_ = null; _output_ = null; _isConnected_ = false; } /** * Returns true if the client is currently connected to a server. *

* @return True if the client is currently connected to a server, * false otherwise. */ public boolean isConnected() { return _isConnected_; } /** * Sets the default port the SocketClient should connect to when a port * is not specified. The _defaultPort_ * variable stores this value. If never set, the default port is equal * to zero. *

* @param port The default port to set. */ public void setDefaultPort(int port) { _defaultPort_ = port; } /** * Returns the current value of the default port (stored in * _defaultPort_ ). *

* @return The current value of the default port. */ public int getDefaultPort() { return _defaultPort_; } /** * Set the default timeout in milliseconds to use when opening a socket. * This value is only used previous to a call to * connect() * and should not be confused with setSoTimeout() * which operates on an the currently opened socket. _timeout_ contains * the new timeout value. *

* @param timeout The timeout in milliseconds to use for the socket * connection. */ public void setDefaultTimeout(int timeout) { _timeout_ = timeout; } /** * Returns the default timeout in milliseconds that is used when * opening a socket. *

* @return The default timeout in milliseconds that is used when * opening a socket. */ public int getDefaultTimeout() { return _timeout_; } /** * Set the timeout in milliseconds of a currently open connection. * Only call this method after a connection has been opened * by connect(). *

* @param timeout The timeout in milliseconds to use for the currently * open socket connection. * @exception SocketException If the operation fails. */ public void setSoTimeout(int timeout) throws SocketException { _socket_.setSoTimeout(timeout); } /** * Returns the timeout in milliseconds of the currently opened socket. *

* @return The timeout in milliseconds of the currently opened socket. * @exception SocketException If the operation fails. */ public int getSoTimeout() throws SocketException { return _socket_.getSoTimeout(); } /** * Enables or disables the Nagle's algorithm (TCP_NODELAY) on the * currently opened socket. *

* @param on True if Nagle's algorithm is to be enabled, false if not. * @exception SocketException If the operation fails. */ public void setTcpNoDelay(boolean on) throws SocketException { _socket_.setTcpNoDelay(on); } /** * Returns true if Nagle's algorithm is enabled on the currently opened * socket. *

* @return True if Nagle's algorithm is enabled on the currently opened * socket, false otherwise. * @exception SocketException If the operation fails. */ public boolean getTcpNoDelay() throws SocketException { return _socket_.getTcpNoDelay(); } /** * Sets the SO_LINGER timeout on the currently opened socket. *

* @param on True if linger is to be enabled, false if not. * @param val The linger timeout (in hundredths of a second?) * @exception SocketException If the operation fails. */ public void setSoLinger(boolean on, int val) throws SocketException { _socket_.setSoLinger(on, val); } /** * Returns the current SO_LINGER timeout of the currently opened socket. *

* @return The current SO_LINGER timeout. If SO_LINGER is disabled returns * -1. * @exception SocketException If the operation fails. */ public int getSoLinger() throws SocketException { return _socket_.getSoLinger(); } /** * Returns the port number of the open socket on the local host used * for the connection. *

* @return The port number of the open socket on the local host used * for the connection. */ public int getLocalPort() { return _socket_.getLocalPort(); } /** * Returns the local address to which the client's socket is bound. *

* @return The local address to which the client's socket is bound. */ public InetAddress getLocalAddress() { return _socket_.getLocalAddress(); } /** * Returns the port number of the remote host to which the client is * connected. *

* @return The port number of the remote host to which the client is * connected. */ public int getRemotePort() { return _socket_.getPort(); } /** * @return The remote address to which the client is connected. */ public InetAddress getRemoteAddress() { return _socket_.getInetAddress(); } /** * Verifies that the remote end of the given socket is connected to the * the same host that the SocketClient is currently connected to. This * is useful for doing a quick security check when a client needs to * accept a connection from a server, such as an FTP data connection or * a BSD R command standard error stream. *

* @return True if the remote hosts are the same, false if not. */ public boolean verifyRemote(Socket socket) { InetAddress host1, host2; host1 = socket.getInetAddress(); host2 = getRemoteAddress(); return host1.equals(host2); } /** * Sets the SocketFactory used by the SocketClient to open socket * connections. If the factory value is null, then a default * factory is used (only do this to reset the factory after having * previously altered it). *

* @param factory The new SocketFactory the SocketClient should use. */ public void setSocketFactory(SocketFactory factory) { if (factory == null) _socketFactory_ = __DEFAULT_SOCKET_FACTORY; else _socketFactory_ = factory; } }

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