SocketChannelpublic abstract class SocketChannel extends AbstractSelectableChannel implements ByteChannel, GatheringByteChannel, ScatteringByteChannel| A selectable channel for stream-oriented connecting sockets.
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.
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.
Socket channels support non-blocking connection: 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.
The input and output sides of a socket channel may independently be
shut down 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 -1, 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}.
Socket channels support asynchronous shutdown, 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 -1. 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}.
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. |
| Constructors Summary |
|---|
protected SocketChannel(SelectorProvider provider)Initializes a new instance of this class.
super(provider);
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| Methods Summary |
|---|
| public abstract boolean | connect(java.net.SocketAddress remote)Connects this channel's socket.
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 true. Otherwise this method returns
false and the connection operation must later be completed by
invoking the {@link #finishConnect finishConnect} method.
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.
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.
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.
| | public abstract boolean | finishConnect()Finishes the process of connecting a socket channel.
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.
If this channel is already connected then this method will not block
and will immediately return true. If this channel is in
non-blocking mode then this method will return false 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 true or throw a checked
exception describing the failure.
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.
| | public abstract boolean | isConnected()Tells whether or not this channel's network socket is connected.
| | public abstract boolean | isConnectionPending()Tells whether or not a connection operation is in progress on this
channel.
| | public static java.nio.channels.SocketChannel | open()Opens a socket channel.
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.
return SelectorProvider.provider().openSocketChannel();
| | public static java.nio.channels.SocketChannel | open(java.net.SocketAddress remote)Opens a socket channel and connects it to a remote address.
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 remote, and then
returning that channel.
SocketChannel sc = open();
sc.connect(remote);
return sc;
| | public abstract int | read(java.nio.ByteBuffer dst)
| | public abstract long | read(java.nio.ByteBuffer[] dsts, int offset, int length)
| | public final long | read(java.nio.ByteBuffer[] dsts)
return read(dsts, 0, dsts.length);
| | public abstract java.net.Socket | socket()Retrieves a socket associated with this channel.
The returned object will not declare any public methods that are not
declared in the {@link java.net.Socket} class.
| | public final int | validOps()Returns an operation set identifying this channel's supported
operations.
Socket channels support connecting, reading, and writing, so this
method returns ({@link SelectionKey#OP_CONNECT}
| {@link SelectionKey#OP_READ} | {@link
SelectionKey#OP_WRITE}).
return (SelectionKey.OP_READ
| SelectionKey.OP_WRITE
| SelectionKey.OP_CONNECT);
| | public abstract int | write(java.nio.ByteBuffer src)
| | public abstract long | write(java.nio.ByteBuffer[] srcs, int offset, int length)
| | public final long | write(java.nio.ByteBuffer[] srcs)
return write(srcs, 0, srcs.length);
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