InetAddress.java (ANY_IF): moved from ServerSocket.

        * java/net/InetAddress.java (ANY_IF): moved from ServerSocket.
        * java/net/DatagramSocket.java (DatagramSocket): use ANY_IF from
        InetAddress.
        * java/net/MulticastSocket.java (MulticastSocket): Likewise.
        * java/net/Socket.java: Merge with Classpath.
        * java/net/ServerSocket.java: Likewise.

From-SVN: r48797

1 files changed, 508 insertions, 112 deletions

diff --git a/libjava/java/net/Socket.java b/libjava/java/net/Socket.java
index 34ea165..6bd6183 100644
--- a/libjava/java/net/Socket.java
+++ b/libjava/java/net/Socket.java
@@ -1,263 +1,659 @@
-// Socket.java
+/* Socket.java -- Client socket implementation
+   Copyright (C) 1998, 1999, 2000, 2002 Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+ 
+GNU Classpath 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+02111-1307 USA.
+
+As a special exception, if you link this library with other files to
+produce an executable, this library does not by itself cause the
+resulting executable to be covered by the GNU General Public License.
+This exception does not however invalidate any other reasons why the
+executable file might be covered by the GNU General Public License. */
 
-/* Copyright (C) 1999  Free Software Foundation
+package java.net;
 
-   This file is part of libgcj.
+import java.io.*;
 
-This software is copyrighted work licensed under the terms of the
-Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
-details.  */
+/* Written using on-line Java Platform 1.2 API Specification.
+ * Status:  I believe all methods are implemented.
+ */
 
 /**
-  * @author Per Bothner <bothner@cygnus.com>
-  * @date January 6, 1999.
-  */
-
-/** Written using on-line Java Platform 1.2 API Specification.
-  * Status:  I believe all methods are implemented.
-  */
-
-package java.net;
-import java.io.*;
-
+ * This class models a client site socket.  A socket is a TCP/IP endpoint
+ * for network communications conceptually similar to a file handle.
+ * <p>
+ * This class does not actually do any work.  Instead, it redirects all of
+ * its calls to a socket implementation object which implements the
+ * <code>SocketImpl</code> interface.  The implementation class is 
+ * instantiated by factory class that implements the 
+ * <code>SocketImplFactory interface</code>.  A default
+ * factory is provided, however the factory may be set by a call to
+ * the <code>setSocketImplFactory</code> method.  Note that this may only be 
+ * done once per virtual machine.  If a subsequent attempt is made to set the
+ * factory, a <code>SocketException</code> will be thrown.
+ *
+ * @author Aaron M. Renn (arenn@urbanophile.com)
+ * @author Per Bothner (bothner@cygnus.com)
+ */
 public class Socket
 {
+
+  // Class Variables
+
+  /**
+   * This is the user SocketImplFactory for this class.  If this variable is
+   * null, a default factory is used.
+   */
   static SocketImplFactory factory;
+
+  // Instance Variables
+
+  /**
+   * The implementation object to which calls are redirected
+   */
   SocketImpl impl;
 
+  // Constructors
+
+  /**
+   * Initializes a new instance of <code>Socket</code> object without 
+   * connecting to a remote host.  This useful for subclasses of socket that 
+   * might want this behavior.
+   */
   protected Socket ()
   {
+    if (factory != null)
+      impl = factory.createSocketImpl();
+    else
+      impl = new PlainSocketImpl();
   }
 
+  /**
+   * Initializes a new instance of <code>Socket</code> object without
+   * connecting to a remote host.  This is useful for subclasses of socket
+   * that might want this behavior.  
+   * <p>
+   * Additionally, this socket will be created using the supplied
+   * implementation class instead the default class or one returned by a
+   * factory.  This value can be <code>null</code>, but if it is, all instance
+   * methods in <code>Socket</code> should be overridden because most of them
+   * rely on this value being populated.
+   *
+   * @param impl The <code>SocketImpl</code> to use for this
+   *             <code>Socket</code>
+   *
+   * @exception SocketException If an error occurs
+   */
   protected Socket (SocketImpl impl) throws SocketException
   {
     this.impl = impl;
   }
 
+  /**
+   * Initializes a new instance of <code>Socket</code> and connects to the 
+   * hostname and port specified as arguments.
+   *
+   * @param host The name of the host to connect to
+   * @param port The port number to connect to
+   *
+   * @exception UnknownHostException If the hostname cannot be resolved to a
+   * network address.
+   * @exception IOException If an error occurs
+   */
   public Socket (String host, int port)
     throws UnknownHostException, IOException
   {
-    this(factory == null ? new PlainSocketImpl() : factory.createSocketImpl());
-    SecurityManager s = System.getSecurityManager();
-    if (s != null)
-      s.checkConnect(host, port);
-    impl.create(true);
-    // FIXME: JCL p. 1586 says if localPort is unspecified, bind to any port,
-    // i.e. '0' and if localAddr is unspecified, use getLocalAddress() as
-    // that default.  JDK 1.2 doc infers not to do a bind.
-    impl.connect(host, port);
+    this(InetAddress.getByName(host), port, null, 0, true);
   }
 
+  /**
+   * Initializes a new instance of <code>Socket</code> and connects to the 
+   * address and port number specified as arguments.
+   *
+   * @param address The address to connect to
+   * @param port The port number to connect to
+   *
+   * @exception IOException If an error occurs
+   */
   public Socket (InetAddress address, int port)
     throws IOException 
   {
-    this(factory == null ? new PlainSocketImpl() : factory.createSocketImpl());
-    SecurityManager s = System.getSecurityManager();
-    if (s != null)
-      s.checkConnect(address.getHostName(), port);
-    impl.create(true);
-    // FIXME: JCL p. 1586 says if localPort is unspecified, bind to any port,
-    // i.e. '0' and if localAddr is unspecified, use getLocalAddress() as
-    // that default.  JDK 1.2 doc infers not to do a bind.
-    impl.connect(address, port);
+    this(address, port, null, 0, true);
   }
 
+  /**
+   * Initializes a new instance of <code>Socket</code> that connects to the 
+   * named host on the specified port and binds to the specified local address 
+   * and port.
+   *
+   * @param host The name of the remote host to connect to.
+   * @param port The remote port to connect to.
+   * @param loadAddr The local address to bind to.
+   * @param localPort The local port to bind to.
+   *
+   * @exception SecurityException If the <code>SecurityManager</code>
+   * exists and does not allow a connection to the specified host/port or
+   * binding to the specified local host/port.
+   * @exception IOException If a connection error occurs.
+   */
   public Socket (String host, int port,
 		 InetAddress localAddr, int localPort) throws IOException
   {
-    this(factory == null ? new PlainSocketImpl() : factory.createSocketImpl());
-    SecurityManager s = System.getSecurityManager();
-    if (s != null)
-      s.checkConnect(host, port);
-    impl.create(true);
-    // FIXME: JCL p. 1587 says if localAddr is null, use getLocalAddress().
-    impl.bind(localAddr, localPort);
-    impl.connect(host, port);
+    this(InetAddress.getByName(host), port, localAddr, localPort, true);
   }
 
+  /**
+   * Initializes a new instance of <code>Socket</code> and connects to the 
+   * address and port number specified as arguments, plus binds to the 
+   * specified local address and port.
+   *
+   * @param address The remote address to connect to
+   * @param port The remote port to connect to
+   * @param localAddr The local address to connect to
+   * @param localPort The local port to connect to
+   *
+   * @exception IOException If an error occurs
+   */
   public Socket (InetAddress address, int port,
 		 InetAddress localAddr, int localPort) throws IOException
   {
-    this(factory == null ? new PlainSocketImpl() : factory.createSocketImpl());
-    SecurityManager s = System.getSecurityManager();
-    if (s != null)
-      s.checkConnect(address.getHostName(), port);
-    impl.create(true);
-    // FIXME: JCL p. 1587 says if localAddr is null, use getLocalAddress().
-    impl.bind(localAddr, localPort);
-    impl.connect(address, port);
+    this(address, port, localAddr, localPort, true);
   }
 
   /**
-   * @deprecated Use DatagramSocket instead for UDP transport.
+   * Initializes a new instance of <code>Socket</code> and connects to the 
+   * hostname and port specified as arguments.  If the stream argument is set 
+   * to <code>true</code>, then a stream socket is created.  If it is 
+   * <code>false</code>, a datagram socket is created.
+   *
+   * @param host The name of the host to connect to
+   * @param port The port to connect to
+   * @param stream <code>true</code> for a stream socket, <code>false</code>
+   * for a datagram socket
+   *
+   * @exception IOException If an error occurs
+   *
+   * @deprecated Use the <code>DatagramSocket</code> class to create
+   * datagram oriented sockets.
    */
   public Socket (String host, int port, boolean stream) throws IOException
   {
-    impl = factory == null ? new PlainSocketImpl()
-      : factory.createSocketImpl();
-    impl.create(stream);
-    SecurityManager s = System.getSecurityManager();
-    if (s != null)
-      s.checkConnect(host, port);
-    // FIXME: JCL p. 1586 says if localPort is unspecified, bind to any port,
-    // i.e. '0' and if localAddr is unspecified, use getLocalAddress() as
-    // that default.  JDK 1.2 doc infers not to do a bind.
-    impl.connect(host, port);
+    this(InetAddress.getByName(host), port, null, 0, stream);
   }
 
   /**
-   * @deprecated Use DatagramSocket instead for UDP transport.
+   * Initializes a new instance of <code>Socket</code> and connects to the 
+   * address and port number specified as arguments.  If the stream param is 
+   * <code>true</code>, a stream socket will be created, otherwise a datagram 
+   * socket is created.
+   *
+   * @param host The address to connect to
+   * @param port The port number to connect to
+   * @param stream <code>true</code> to create a stream socket, 
+   * <code>false</code> to create a datagram socket.
+   *
+   * @exception IOException If an error occurs
+   *
+   * @deprecated Use the <code>DatagramSocket</code> class to create
+   * datagram oriented sockets.
    */
   public Socket (InetAddress host, int port, boolean stream) throws IOException
   {
-    impl = factory == null ? new PlainSocketImpl()
-      : factory.createSocketImpl();
+    this(host, port, null, 0, stream);
+  }
+
+  /**
+   * This constructor is where the real work takes place.  Connect to the
+   * specified address and port.  Use default local values if not specified,
+   * otherwise use the local host and port passed in.  Create as stream or
+   * datagram based on "stream" argument.
+   * <p>
+   *
+   * @param raddr The remote address to connect to
+   * @param rport The remote port to connect to
+   * @param laddr The local address to connect to
+   * @param lport The local port to connect to
+   * @param stream true for a stream socket, false for a datagram socket
+   *
+   * @exception IOException If an error occurs
+   */
+  private Socket(InetAddress raddr, int rport, InetAddress laddr, int lport,
+                 boolean stream) throws IOException
+  {
+    this();
+    if (impl == null)
+      throw new IOException("Cannot initialize Socket implementation");
+
+    SecurityManager sm = System.getSecurityManager();
+    if (sm != null)
+      sm.checkConnect(raddr.getHostName(), rport);
+
     impl.create(stream);
-    SecurityManager s = System.getSecurityManager();
-    if (s != null)
-      s.checkConnect(host.getHostName(), port);
+
     // FIXME: JCL p. 1586 says if localPort is unspecified, bind to any port,
     // i.e. '0' and if localAddr is unspecified, use getLocalAddress() as
     // that default.  JDK 1.2 doc infers not to do a bind.
-    impl.connect(host, port);
+    if (laddr != null)
+      impl.bind(laddr, lport);
+
+    if (raddr != null)
+      impl.connect(raddr, rport);
   }
 
+  /**
+   * Returns the address of the remote end of the socket.  If this socket
+   * is not connected, then <code>null</code> is returned.
+   *
+   * @return The remote address this socket is connected to
+   */
   public InetAddress getInetAddress ()
   {
-    return impl.getInetAddress();
+    if (impl != null)
+      return impl.getInetAddress();
+
+    return null;
   }
 
+  /**
+   * Returns the local address to which this socket is bound.  If this socket
+   * is not connected, then <code>null</code> is returned.
+   *
+   * @return The local address
+   */
   public InetAddress getLocalAddress ()
   {
-    // FIXME: see note in DatagramSocket.java about checkConnect() and security
+    if (impl == null)
+      return null;
+
+    InetAddress addr = null;
     try
       {
-	return (InetAddress)impl.getOption(SocketOptions.SO_BINDADDR);
+        addr = (InetAddress)impl.getOption(SocketOptions.SO_BINDADDR);
       }
-    catch (SocketException x)
+    catch(SocketException e)
       {
-	// (hopefully) shouldn't happen
-	System.err.println(x);
-        throw new java.lang.InternalError("Error in PlainSocketImpl.getOption");
+        // (hopefully) shouldn't happen
+        // throw new java.lang.InternalError
+        //      ("Error in PlainSocketImpl.getOption");
+        return null;
       }
+
+    // FIXME: According to libgcj, checkConnect() is supposed to be called
+    // before performing this operation.  Problems: 1) We don't have the
+    // addr until after we do it, so we do a post check.  2). The docs I
+    // see don't require this in the Socket case, only DatagramSocket, but
+    // we'll assume they mean both.
+    SecurityManager sm = System.getSecurityManager();
+    if (sm != null)
+      sm.checkConnect(addr.getHostName(), getLocalPort());
+
+    return addr;
   }
 
+  /**
+   * Returns the port number of the remote end of the socket connection.  If
+   * this socket is not connected, then -1 is returned.
+   *
+   * @return The remote port this socket is connected to
+   */
   public int getPort ()
   {
-    return impl.getPort();
+    if (impl != null)
+      return impl.getPort();
+
+    return -1;
   }
 
+  /**
+   * Returns the local port number to which this socket is bound.  If this
+   * socket is not connected, then -1 is returned.
+   *
+   * @return The local port
+   */
   public int getLocalPort ()
   {
-    return impl.getLocalPort();
+    if (impl != null)
+      return impl.getLocalPort();
+
+    return -1;
   }
 
+  /**
+   * Returns an InputStream for reading from this socket.
+   *
+   * @return The InputStream object
+   *
+   * @exception IOException If an error occurs or Socket is not connected
+   */
   public InputStream getInputStream () throws IOException
   {
-    return impl.getInputStream();
+    if (impl != null)
+      return(impl.getInputStream());
+
+    throw new IOException("Not connected");
   }
 
+  /**
+   * Returns an OutputStream for writing to this socket.
+   *
+   * @return The OutputStream object
+   *
+   * @exception IOException If an error occurs or Socket is not connected
+   */
   public OutputStream getOutputStream () throws IOException
   {
-    return impl.getOutputStream();
+    if (impl != null)
+      return impl.getOutputStream();
+
+    throw new IOException("Not connected");
   }
 
+  /**
+   * Sets the TCP_NODELAY option on the socket. 
+   *
+   * @param on true to enable, false to disable
+   * 
+   * @exception SocketException If an error occurs or Socket is not connected
+   */
   public void setTcpNoDelay (boolean on)  throws SocketException
   {
-    impl.setOption( SocketOptions.TCP_NODELAY, new Boolean(on) );
+    if (impl == null)
+      throw new SocketException("Not connected");
+
+    impl.setOption(SocketOptions.TCP_NODELAY, new Boolean(on));
   }
 
+  /**
+   * Tests whether or not the TCP_NODELAY option is set on the socket. 
+   * Returns true if enabled, false if disabled. When on it disables the
+   * Nagle algorithm which means that packets are always send immediatly and
+   * never merged together to reduce network trafic.
+   *
+   * @return Whether or not TCP_NODELAY is set
+   * 
+   * @exception SocketException If an error occurs or Socket not connected
+   */
   public boolean getTcpNoDelay() throws SocketException
   {
-    Boolean bool = (Boolean)impl.getOption( SocketOptions.TCP_NODELAY );
-    return bool.booleanValue();
+    if (impl == null)
+      throw new SocketException("Not connected");
+
+    Object on = impl.getOption(SocketOptions.TCP_NODELAY);
+  
+    if (on instanceof Boolean)
+      return(((Boolean)on).booleanValue());
+    else
+      throw new SocketException("Internal Error");
   }
 
+  /**
+   * Sets the value of the SO_LINGER option on the socket.  If the 
+   * SO_LINGER option is set on a socket and there is still data waiting to
+   * be sent when the socket is closed, then the close operation will block
+   * until either that data is delivered or until the timeout period
+   * expires.  The linger interval is specified in hundreths of a second
+   * (platform specific?)
+   *
+   * @param on true to enable SO_LINGER, false to disable
+   * @param linger The SO_LINGER timeout in hundreths of a second or -1 if 
+   * SO_LINGER not set.
+   *
+   * @exception SocketException If an error occurs or Socket not connected
+   */
   public void setSoLinger(boolean on, int linger) throws SocketException
   {
-    if ( on && (linger >= 0) ) 
+    if (impl == null)
+      throw new SocketException("No socket created");
+
+    if (on == true)
       {
-	if (linger > 65535)
-	  linger = 65535;
-	impl.setOption( SocketOptions.SO_LINGER, new Integer(linger) );
-      } 
-    else if ( on && (linger < 0) ) 
-      throw new IllegalArgumentException("SO_LINGER must be >= 0");
+        if (linger < 0)
+          throw new IllegalArgumentException("SO_LINGER must be >= 0");
+
+        if (linger > 65535)
+          linger = 65535;
+
+        impl.setOption(SocketOptions.SO_LINGER, new Integer(linger));
+      }
     else
-      impl.setOption( SocketOptions.SO_LINGER, new Boolean(false) );
+      {
+        impl.setOption(SocketOptions.SO_LINGER, new Boolean(false));
+      }
   }
 
+  /**
+   * Returns the value of the SO_LINGER option on the socket.  If the 
+   * SO_LINGER option is set on a socket and there is still data waiting to
+   * be sent when the socket is closed, then the close operation will block
+   * until either that data is delivered or until the timeout period
+   * expires.  This method either returns the timeouts (in hundredths of
+   * of a second (platform specific?)) if SO_LINGER is set, or -1 if
+   * SO_LINGER is not set.
+   *
+   * @return The SO_LINGER timeout in hundreths of a second or -1 
+   * if SO_LINGER not set
+   *
+   * @exception SocketException If an error occurs or Socket is not connected
+   */
   public int getSoLinger() throws SocketException
   {
-    Object linger = impl.getOption(SocketOptions.SO_LINGER);    
-    if (linger instanceof Integer) 
-      return ((Integer)linger).intValue();
+    if (impl == null)
+      throw new SocketException("Not connected");
+
+    Object linger = impl.getOption(SocketOptions.SO_LINGER);
+    if (linger instanceof Integer)
+      return(((Integer)linger).intValue());
     else
       return -1;
   }
 
+  /**
+   * Sets the value of the SO_TIMEOUT option on the socket.  If this value
+   * is set, and an read/write is performed that does not complete within
+   * the timeout period, a short count is returned (or an EWOULDBLOCK signal
+   * would be sent in Unix if no data had been read).  A value of 0 for
+   * this option implies that there is no timeout (ie, operations will 
+   * block forever).  On systems that have separate read and write timeout
+   * values, this method returns the read timeout.  This
+   * value is in thousandths of a second (****????*****)
+   *
+   * @param timeout The length of the timeout in thousandth's of a second or 
+   * 0 if not set
+   *
+   * @exception SocketException If an error occurs or Socket not connected
+   */
   public synchronized void setSoTimeout (int timeout) throws SocketException
   {
+    if (impl == null)
+      throw new SocketException("Not connected");
+    
     if (timeout < 0)
-      throw new IllegalArgumentException("Invalid timeout: " + timeout);
-
+      throw new IllegalArgumentException("SO_TIMEOUT value must be >= 0");
+      
     impl.setOption(SocketOptions.SO_TIMEOUT, new Integer(timeout));
   }
 
+  /**
+   * Returns the value of the SO_TIMEOUT option on the socket.  If this value
+   * is set, and an read/write is performed that does not complete within
+   * the timeout period, a short count is returned (or an EWOULDBLOCK signal
+   * would be sent in Unix if no data had been read).  A value of 0 for
+   * this option implies that there is no timeout (ie, operations will 
+   * block forever).  On systems that have separate read and write timeout
+   * values, this method returns the read timeout.  This
+   * value is in thousandths of a second (implementation specific?).
+   *
+   * @return The length of the timeout in thousandth's of a second or 0 
+   * if not set
+   *
+   * @exception SocketException If an error occurs or Socket not connected
+   */
   public synchronized int getSoTimeout () throws SocketException
   {
+    if (impl == null) 
+      throw new SocketException("Not connected");
+
     Object timeout = impl.getOption(SocketOptions.SO_TIMEOUT);
-    if (timeout instanceof Integer) 
-      return ((Integer)timeout).intValue();
+    if (timeout instanceof Integer)
+      return(((Integer)timeout).intValue());
     else
       return 0;
   }
 
-  // JDK1.2
+  /**
+   * This method sets the value for the system level socket option
+   * SO_SNDBUF to the specified value.  Note that valid values for this
+   * option are specific to a given operating system.
+   *
+   * @param size The new send buffer size.
+   *
+   * @exception SocketException If an error occurs or Socket not connected
+   *
+   * @since Java 1.2
+   */
   public void setSendBufferSize (int size) throws SocketException
   {
+    if (impl == null)
+      throw new SocketException("Not connected");
+    
     if (size <= 0)
-      throw new IllegalArgumentException("Invalid buffer size: " + size);
-
+      throw new IllegalArgumentException("SO_SNDBUF value must be > 0");
+    
     impl.setOption(SocketOptions.SO_SNDBUF, new Integer(size));
   }
 
-  // JDK1.2
+  /**
+   * This method returns the value of the system level socket option
+   * SO_SNDBUF, which is used by the operating system to tune buffer
+   * sizes for data transfers.
+   *
+   * @return The send buffer size.
+   *
+   * @exception SocketException If an error occurs or socket not connected
+   *
+   * @since Java 1.2
+   */
   public int getSendBufferSize () throws SocketException
   {
-    Integer buf = (Integer)impl.getOption(SocketOptions.SO_SNDBUF);
-    return buf.intValue();
+    if (impl == null)
+      throw new SocketException("Not connected");
+
+    Object buf = impl.getOption(SocketOptions.SO_SNDBUF);
+
+    if (buf instanceof Integer)
+      return(((Integer)buf).intValue());
+    else
+      throw new SocketException("Internal Error: Unexpected type");
   }
 
-  // JDK1.2
+  /**
+   * This method sets the value for the system level socket option
+   * SO_RCVBUF to the specified value.  Note that valid values for this
+   * option are specific to a given operating system.
+   *
+   * @param size The new receive buffer size.
+   *
+   * @exception SocketException If an error occurs or Socket is not connected
+   *
+   * @since Java 1.2
+   */
   public void setReceiveBufferSize (int size) throws SocketException
   {
-    if (size <= 0)
-      throw new IllegalArgumentException("Invalid buffer size: " + size);
+    if (impl == null)
+      throw new SocketException("Not connected");
 
+    if (size <= 0)
+      throw new IllegalArgumentException("SO_RCVBUF value must be > 0");
+      
     impl.setOption(SocketOptions.SO_RCVBUF, new Integer(size));
   }
 
-  // JDK1.2
+  /**
+   * This method returns the value of the system level socket option
+   * SO_RCVBUF, which is used by the operating system to tune buffer
+   * sizes for data transfers.
+   *
+   * @return The receive buffer size.
+   *
+   * @exception SocketException If an error occurs or Socket is not connected
+   *
+   * @since Java 1.2
+   */
   public int getReceiveBufferSize () throws SocketException
   {
-    Integer buf = (Integer)impl.getOption(SocketOptions.SO_RCVBUF);
-    return buf.intValue();
+    if (impl == null)
+      throw new SocketException("Not connected");
+
+    Object buf = impl.getOption(SocketOptions.SO_RCVBUF);
+
+    if (buf instanceof Integer)
+      return(((Integer)buf).intValue());
+    else
+      throw new SocketException("Internal Error: Unexpected type");
   }
 
+  /**
+   * Closes the socket.
+   *
+   * @exception IOException If an error occurs
+   */
   public synchronized void close ()  throws IOException
   {
-    impl.close();
+    if (impl != null)
+      impl.close();
   }
 
+  /**
+   * Converts this <code>Socket</code> to a <code>String</code>.
+   *
+   * @return The <code>String</code> representation of this <code>Socket</code>
+   */
   public String toString ()
   {
-    return "Socket" + impl.toString();
+    return("Socket " + impl);
   }
 
+  // Class Methods
+
+  /**
+   * Sets the <code>SocketImplFactory</code>.  This may be done only once per 
+   * virtual machine.  Subsequent attempts will generate a 
+   * <code>SocketException</code>.  Note that a <code>SecurityManager</code>
+   * check is made prior to setting the factory.  If 
+   * insufficient privileges exist to set the factory, then an 
+   * <code>IOException</code> will be thrown.
+   *
+   * @exception SecurityException If the <code>SecurityManager</code> does
+   * not allow this operation.
+   * @exception SocketException If the SocketImplFactory is already defined
+   * @exception IOException If any other error occurs
+   */
   public static synchronized void setSocketImplFactory (SocketImplFactory fac)
     throws IOException
   {
+    // See if already set
+    if (factory != null)
+      throw new SocketException("SocketImplFactory already defined");
+
+    // Check permissions
+    SecurityManager sm = System.getSecurityManager();
+    if (sm != null)
+      sm.checkSetFactory();
+
     factory = fac;
   }
 }