/*
* @(#)SocketChannel.java 1.33 03/12/19
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.nio.channels;
import java.io.IOException;
import java.net.Socket;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.spi.*;
/**
* A selectable channel for stream-oriented connecting sockets.
*
* <p> Socket channels are not a complete abstraction of connecting network
* sockets. Binding, shutdown, and the manipulation of socket options must be
* done through an associated {@link java.net.Socket} object obtained by
* invoking the {@link #socket() socket} method. It is not possible to create
* a channel for an arbitrary, pre-existing socket, nor is it possible to
* specify the {@link java.net.SocketImpl} object to be used by a socket
* associated with a socket channel.
*
* <p> A socket channel is created by invoking one of the {@link #open open}
* methods of this class. A newly-created socket channel is open but not yet
* connected. An attempt to invoke an I/O operation upon an unconnected
* channel will cause a {@link NotYetConnectedException} to be thrown. A
* socket channel can be connected by invoking its {@link #connect connect}
* method; once connected, a socket channel remains connected until it is
* closed. Whether or not a socket channel is connected may be determined by
* invoking its {@link #isConnected isConnected} method.
*
* <p> Socket channels support <i>non-blocking connection:</i> A socket
* channel may be created and the process of establishing the link to the
* remote socket may be initiated via the {@link #connect connect} method for
* later completion by the {@link #finishConnect finishConnect} method.
* Whether or not a connection operation is in progress may be determined by
* invoking the {@link #isConnectionPending isConnectionPending} method.
*
* <p> The input and output sides of a socket channel may independently be
* <i>shut down</i> without actually closing the channel. Shutting down the
* input side of a channel by invoking the {@link java.net.Socket#shutdownInput
* shutdownInput} method of an associated socket object will cause further
* reads on the channel to return <tt>-1</tt>, the end-of-stream indication.
* Shutting down the output side of the channel by invoking the {@link
* java.net.Socket#shutdownOutput shutdownOutput} method of an associated
* socket object will cause further writes on the channel to throw a {@link
* ClosedChannelException}.
*
* <p> Socket channels support <i>asynchronous shutdown,</i> which is similar
* to the asynchronous close operation specified in the {@link Channel} class.
* If the input side of a socket is shut down by one thread while another
* thread is blocked in a read operation on the socket's channel, then the read
* operation in the blocked thread will complete without reading any bytes and
* will return <tt>-1</tt>. If the output side of a socket is shut down by one
* thread while another thread is blocked in a write operation on the socket's
* channel, then the blocked thread will receive an {@link
* AsynchronousCloseException}.
*
* <p> Socket channels are safe for use by multiple concurrent threads. They
* support concurrent reading and writing, though at most one thread may be
* reading and at most one thread may be writing at any given time. The {@link
* #connect connect} and {@link #finishConnect finishConnect} methods are
* mutually synchronized against each other, and an attempt to initiate a read
* or write operation while an invocation of one of these methods is in
* progress will block until that invocation is complete. </p>
*
*
* @author Mark Reinhold
* @author JSR-51 Expert Group
* @version 1.33, 03/12/19
* @since 1.4
*/
public abstract class SocketChannel
extends AbstractSelectableChannel
implements ByteChannel, ScatteringByteChannel, GatheringByteChannel
{
/**
* Initializes a new instance of this class.
*/
protected SocketChannel(SelectorProvider provider) {
super(provider);
}
/**
* Opens a socket channel.
*
* <p> The new channel is created by invoking the {@link
* java.nio.channels.spi.SelectorProvider#openSocketChannel
* openSocketChannel} method of the system-wide default {@link
* java.nio.channels.spi.SelectorProvider} object. </p>
*
* @return A new socket channel
*
* @throws IOException
* If an I/O error occurs
*/
public static SocketChannel open() throws IOException {
return SelectorProvider.provider().openSocketChannel();
}
/**
* Opens a socket channel and connects it to a remote address.
*
* <p> This convenience method works as if by invoking the {@link #open()}
* method, invoking the {@link #connect(SocketAddress) connect} method upon
* the resulting socket channel, passing it <tt>remote</tt>, and then
* returning that channel. </p>
*
* @param remote
* The remote address to which the new channel is to be connected
*
* @throws AsynchronousCloseException
* If another thread closes this channel
* while the connect operation is in progress
*
* @throws ClosedByInterruptException
* If another thread interrupts the current thread
* while the connect operation is in progress, thereby
* closing the channel and setting the current thread's
* interrupt status
*
* @throws UnresolvedAddressException
* If the given remote address is not fully resolved
*
* @throws UnsupportedAddressTypeException
* If the type of the given remote address is not supported
*
* @throws SecurityException
* If a security manager has been installed
* and it does not permit access to the given remote endpoint
*
* @throws IOException
* If some other I/O error occurs
*/
public static SocketChannel open(SocketAddress remote)
throws IOException
{
SocketChannel sc = open();
sc.connect(remote);
return sc;
}
/**
* Returns an operation set identifying this channel's supported
* operations.
*
* <p> Socket channels support connecting, reading, and writing, so this
* method returns <tt>(</tt>{@link SelectionKey#OP_CONNECT}
* <tt>|</tt> {@link SelectionKey#OP_READ} <tt>|</tt> {@link
* SelectionKey#OP_WRITE}<tt>)</tt>. </p>
*
* @return The valid-operation set
*/
public final int validOps() {
return (SelectionKey.OP_READ
| SelectionKey.OP_WRITE
| SelectionKey.OP_CONNECT);
}
// -- Socket-specific operations --
/**
* Retrieves a socket associated with this channel.
*
* <p> The returned object will not declare any public methods that are not
* declared in the {@link java.net.Socket} class. </p>
*
* @return A socket associated with this channel
*/
public abstract Socket socket();
/**
* Tells whether or not this channel's network socket is connected. </p>
*
* @return <tt>true</tt> if, and only if, this channel's network socket
* is connected
*/
public abstract boolean isConnected();
/**
* Tells whether or not a connection operation is in progress on this
* channel. </p>
*
* @return <tt>true</tt> if, and only if, a connection operation has been
* initiated on this channel but not yet completed by invoking the
* {@link #finishConnect finishConnect} method
*/
public abstract boolean isConnectionPending();
/**
* Connects this channel's socket.
*
* <p> If this channel is in non-blocking mode then an invocation of this
* method initiates a non-blocking connection operation. If the connection
* is established immediately, as can happen with a local connection, then
* this method returns <tt>true</tt>. Otherwise this method returns
* <tt>false</tt> and the connection operation must later be completed by
* invoking the {@link #finishConnect finishConnect} method.
*
* <p> If this channel is in blocking mode then an invocation of this
* method will block until the connection is established or an I/O error
* occurs.
*
* <p> This method performs exactly the same security checks as the {@link
* java.net.Socket} class. That is, if a security manager has been
* installed then this method verifies that its {@link
* java.lang.SecurityManager#checkConnect checkConnect} method permits
* connecting to the address and port number of the given remote endpoint.
*
* <p> This method may be invoked at any time. If a read or write
* operation upon this channel is invoked while an invocation of this
* method is in progress then that operation will first block until this
* invocation is complete. If a connection attempt is initiated but fails,
* that is, if an invocation of this method throws a checked exception,
* then the channel will be closed. </p>
*
* @param remote
* The remote address to which this channel is to be connected
*
* @return <tt>true</tt> if a connection was established,
* <tt>false</tt> if this channel is in non-blocking mode
* and the connection operation is in progress
*
* @throws AlreadyConnectedException
* If this channel is already connected
*
* @throws ConnectionPendingException
* If a non-blocking connection operation is already in progress
* on this channel
*
* @throws ClosedChannelException
* If this channel is closed
*
* @throws AsynchronousCloseException
* If another thread closes this channel
* while the connect operation is in progress
*
* @throws ClosedByInterruptException
* If another thread interrupts the current thread
* while the connect operation is in progress, thereby
* closing the channel and setting the current thread's
* interrupt status
*
* @throws UnresolvedAddressException
* If the given remote address is not fully resolved
*
* @throws UnsupportedAddressTypeException
* If the type of the given remote address is not supported
*
* @throws SecurityException
* If a security manager has been installed
* and it does not permit access to the given remote endpoint
*
* @throws IOException
* If some other I/O error occurs
*/
public abstract boolean connect(SocketAddress remote) throws IOException;
/**
* Finishes the process of connecting a socket channel.
*
* <p> A non-blocking connection operation is initiated by placing a socket
* channel in non-blocking mode and then invoking its {@link #connect
* connect} method. Once the connection is established, or the attempt has
* failed, the socket channel will become connectable and this method may
* be invoked to complete the connection sequence. If the connection
* operation failed then invoking this method will cause an appropriate
* {@link java.io.IOException} to be thrown.
*
* <p> If this channel is already connected then this method will not block
* and will immediately return <tt>true</tt>. If this channel is in
* non-blocking mode then this method will return <tt>false</tt> if the
* connection process is not yet complete. If this channel is in blocking
* mode then this method will block until the connection either completes
* or fails, and will always either return <tt>true</tt> or throw a checked
* exception describing the failure.
*
* <p> This method may be invoked at any time. If a read or write
* operation upon this channel is invoked while an invocation of this
* method is in progress then that operation will first block until this
* invocation is complete. If a connection attempt fails, that is, if an
* invocation of this method throws a checked exception, then the channel
* will be closed. </p>
*
* @return <tt>true</tt> if, and only if, this channel's socket is now
* connected
*
* @throws NoConnectionPendingException
* If this channel is not connected and a connection operation
* has not been initiated
*
* @throws ClosedChannelException
* If this channel is closed
*
* @throws AsynchronousCloseException
* If another thread closes this channel
* while the connect operation is in progress
*
* @throws ClosedByInterruptException
* If another thread interrupts the current thread
* while the connect operation is in progress, thereby
* closing the channel and setting the current thread's
* interrupt status
*
* @throws IOException
* If some other I/O error occurs
*/
public abstract boolean finishConnect() throws IOException;
// -- ByteChannel operations --
/**
* @throws NotYetConnectedException
* If this channel is not yet connected
*/
public abstract int read(ByteBuffer dst) throws IOException;
/**
* @throws NotYetConnectedException
* If this channel is not yet connected
*/
public abstract long read(ByteBuffer[] dsts, int offset, int length)
throws IOException;
/**
* @throws NotYetConnectedException
* If this channel is not yet connected
*/
public final long read(ByteBuffer[] dsts) throws IOException {
return read(dsts, 0, dsts.length);
}
/**
* @throws NotYetConnectedException
* If this channel is not yet connected
*/
public abstract int write(ByteBuffer src) throws IOException;
/**
* @throws NotYetConnectedException
* If this channel is not yet connected
*/
public abstract long write(ByteBuffer[] srcs, int offset, int length)
throws IOException;
/**
* @throws NotYetConnectedException
* If this channel is not yet connected
*/
public final long write(ByteBuffer[] srcs) throws IOException {
return write(srcs, 0, srcs.length);
}
}
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