Module java.base
Package java.nio.channels

Class SocketChannel

java.lang.Object
java.nio.channels.spi.AbstractInterruptibleChannel
java.nio.channels.SelectableChannel
java.nio.channels.spi.AbstractSelectableChannel
java.nio.channels.SocketChannel
All Implemented Interfaces:
Closeable, AutoCloseable, ByteChannel, Channel, GatheringByteChannel, InterruptibleChannel, NetworkChannel, ReadableByteChannel, ScatteringByteChannel, WritableByteChannel
public abstract class SocketChannel extends AbstractSelectableChannel implements ByteChannel, ScatteringByteChannel, GatheringByteChannel, NetworkChannel
A selectable channel for stream-oriented connecting sockets.

A socket channel is created by invoking one of the open methods of this class. The no-arg open method opens a socket channel for an Internet protocol socket. The open(ProtocolFamily) method is used to open a socket channel for a socket of a specified protocol family. It is not possible to create a channel for an arbitrary, pre-existing socket. 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 NotYetConnectedException to be thrown. A socket channel can be connected by invoking its 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 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 connect method for later completion by the finishConnect method. Whether or not a connection operation is in progress may be determined by invoking the isConnectionPending method.

Socket channels support asynchronous shutdown, which is similar to the asynchronous close operation specified in the 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 AsynchronousCloseException.

Socket options are configured using the setOption method. Socket channels for Internet protocol sockets support following options:

Socket options
Option Name Description
SO_SNDBUF The size of the socket send buffer
SO_RCVBUF The size of the socket receive buffer
SO_KEEPALIVE Keep connection alive
SO_REUSEADDR Re-use address
SO_LINGER Linger on close if data is present (when configured in blocking mode only)
TCP_NODELAY Disable the Nagle algorithm

Socket channels for Unix domain sockets support:

Socket options
Option Name Description
SO_SNDBUF The size of the socket send buffer
SO_RCVBUF The size of the socket receive buffer
SO_LINGER Linger on close if data is present (when configured in blocking mode only)

Additional (implementation specific) options may also be supported.

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 connect and 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.

Since:
1.4