SocketImpl

public abstract class SocketImpl extends Object
implements SocketOptions

The abstract class SocketImpl is a common superclass of all classes that actually implement sockets. It is used to create both client and server sockets.

A "plain" socket implements these methods exactly as described, without attempting to go through a firewall or proxy.

Inherited Constant Summary

From interface java.net.SocketOptions

int	IP_MULTICAST_IF	Set which outgoing interface on which to send multicast packets.
int	IP_MULTICAST_IF2	Same as above.
int	IP_MULTICAST_LOOP	This option enables or disables local loopback of multicast datagrams.
int	IP_TOS	This option sets the type-of-service or traffic class field in the IP header for a TCP or UDP socket.
int	SO_BINDADDR	Fetch the local address binding of a socket (this option cannot be "set" only "gotten", since sockets are bound at creation time, and so the locally bound address cannot be changed).
int	SO_BROADCAST	Sets SO_BROADCAST for a socket.
int	SO_KEEPALIVE	When the keepalive option is set for a TCP socket and no data has been exchanged across the socket in either direction for 2 hours (NOTE: the actual value is implementation dependent), TCP automatically sends a keepalive probe to the peer.
int	SO_LINGER	Specify a linger-on-close timeout.
int	SO_OOBINLINE	When the OOBINLINE option is set, any TCP urgent data received on the socket will be received through the socket input stream.
int	SO_RCVBUF	Set a hint the size of the underlying buffers used by the platform for incoming network I/O.
int	SO_REUSEADDR	Sets SO_REUSEADDR for a socket.
int	SO_SNDBUF	Set a hint the size of the underlying buffers used by the platform for outgoing network I/O.
int	SO_TIMEOUT	Set a timeout on blocking Socket operations: ServerSocket.accept(); SocketInputStream.read(); DatagramSocket.receive(); The option must be set prior to entering a blocking operation to take effect.
int	TCP_NODELAY	Disable Nagle's algorithm for this connection.

Field Summary

protected InetAddress	address	The IP address of the remote end of this socket.
protected FileDescriptor	fd	The file descriptor object for this socket.
protected int	localport	The local port number to which this socket is connected.
protected int	port	The port number on the remote host to which this socket is connected.

Public Constructor Summary

SocketImpl()

Public Method Summary

String

toString() Returns the address and port of this socket as a String.

Protected Method Summary

abstract void	accept(SocketImpl s) Accepts a connection.
abstract int	available() Returns the number of bytes that can be read from this socket without blocking.
abstract void	bind(InetAddress host, int port) Binds this socket to the specified local IP address and port number.
abstract void	close() Closes this socket.
abstract void	connect(InetAddress address, int port) Connects this socket to the specified port number on the specified host.
abstract void	connect(SocketAddress address, int timeout) Connects this socket to the specified port number on the specified host.
abstract void	connect(String host, int port) Connects this socket to the specified port on the named host.
abstract void	create(boolean stream) Creates either a stream or a datagram socket.
FileDescriptor	getFileDescriptor() Returns the value of this socket's fd field.
InetAddress	getInetAddress() Returns the value of this socket's address field.
abstract InputStream	getInputStream() Returns an input stream for this socket.
int	getLocalPort() Returns the value of this socket's localport field.
abstract OutputStream	getOutputStream() Returns an output stream for this socket.
int	getPort() Returns the value of this socket's port field.
abstract void	listen(int backlog) Sets the maximum queue length for incoming connection indications (a request to connect) to the count argument.
abstract void	sendUrgentData(int data) Send one byte of urgent data on the socket.
void	setPerformancePreferences(int connectionTime, int latency, int bandwidth) Sets performance preferences for this socket.
void	shutdownInput() Places the input stream for this socket at "end of stream".
void	shutdownOutput() Disables the output stream for this socket.
boolean	supportsUrgentData() Returns whether or not this SocketImpl supports sending urgent data.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.net.SocketOptions

abstract Object	getOption(int optID) Fetch the value of an option.
abstract void	setOption(int optID, Object value) Enable/disable the option specified by optID.

Fields

protected InetAddress address

The IP address of the remote end of this socket.

protected FileDescriptor fd

The file descriptor object for this socket.

protected int localport

The local port number to which this socket is connected.

protected int port

The port number on the remote host to which this socket is connected.

Public Constructors

public SocketImpl ()

Public Methods

public String toString ()

Returns the address and port of this socket as a String.

Returns

• a string representation of this socket.

Protected Methods

protected abstract void accept (SocketImpl s)

Accepts a connection.

Parameters

s	the accepted connection.

Throws

IOException	if an I/O error occurs when accepting the connection.

protected abstract int available ()

Returns the number of bytes that can be read from this socket without blocking.

Returns

• the number of bytes that can be read from this socket without blocking.

Throws

IOException	if an I/O error occurs when determining the number of bytes available.

protected abstract void bind (InetAddress host, int port)

Binds this socket to the specified local IP address and port number.

Parameters

host	an IP address that belongs to a local interface.
port	the port number.

Throws

IOException	if an I/O error occurs when binding this socket.

protected abstract void close ()

Closes this socket.

Throws

IOException	if an I/O error occurs when closing this socket.

protected abstract void connect (InetAddress address, int port)

Connects this socket to the specified port number on the specified host.

Parameters

address	the IP address of the remote host.
port	the port number.

Throws

IOException	if an I/O error occurs when attempting a connection.

protected abstract void connect (SocketAddress address, int timeout)

Connects this socket to the specified port number on the specified host. A timeout of zero is interpreted as an infinite timeout. The connection will then block until established or an error occurs.

Parameters

address	the Socket address of the remote host.
timeout	the timeout value, in milliseconds, or zero for no timeout.

Throws

IOException	if an I/O error occurs when attempting a connection.

protected abstract void connect (String host, int port)

Connects this socket to the specified port on the named host.

Parameters

host	the name of the remote host.
port	the port number.

Throws

IOException	if an I/O error occurs when connecting to the remote host.

protected abstract void create (boolean stream)

Creates either a stream or a datagram socket.

Parameters

stream	if true, create a stream socket; otherwise, create a datagram socket.

Throws

IOException	if an I/O error occurs while creating the socket.

protected FileDescriptor getFileDescriptor ()

Returns the value of this socket's fd field.

Returns

• the value of this socket's fd field.

See Also

• fd

protected InetAddress getInetAddress ()

Returns the value of this socket's address field.

Returns

• the value of this socket's address field.

See Also

• address

protected abstract InputStream getInputStream ()

Returns an input stream for this socket.

Returns

• a stream for reading from this socket.

Throws

IOException	if an I/O error occurs when creating the input stream.

protected int getLocalPort ()

Returns the value of this socket's localport field.

Returns

• the value of this socket's localport field.

See Also

• localport

protected abstract OutputStream getOutputStream ()

Returns an output stream for this socket.

Returns

• an output stream for writing to this socket.

Throws

IOException	if an I/O error occurs when creating the output stream.

protected int getPort ()

Returns the value of this socket's port field.

Returns

• the value of this socket's port field.

See Also

• port

protected abstract void listen (int backlog)

Sets the maximum queue length for incoming connection indications (a request to connect) to the count argument. If a connection indication arrives when the queue is full, the connection is refused.

Parameters

backlog	the maximum length of the queue.

Throws

IOException	if an I/O error occurs when creating the queue.

protected abstract void sendUrgentData (int data)

Send one byte of urgent data on the socket. The byte to be sent is the low eight bits of the parameter

Parameters

data	The byte of data to send

Throws

IOException	if there is an error sending the data.

protected void setPerformancePreferences (int connectionTime, int latency, int bandwidth)

Sets performance preferences for this socket.

Sockets use the TCP/IP protocol by default. Some implementations may offer alternative protocols which have different performance characteristics than TCP/IP. This method allows the application to express its own preferences as to how these tradeoffs should be made when the implementation chooses from the available protocols.

Performance preferences are described by three integers whose values indicate the relative importance of short connection time, low latency, and high bandwidth. The absolute values of the integers are irrelevant; in order to choose a protocol the values are simply compared, with larger values indicating stronger preferences. Negative values represent a lower priority than positive values. If the application prefers short connection time over both low latency and high bandwidth, for example, then it could invoke this method with the values (1, 0, 0). If the application prefers high bandwidth above low latency, and low latency above short connection time, then it could invoke this method with the values (0, 1, 2). By default, this method does nothing, unless it is overridden in a a sub-class.

Parameters

connectionTime	An int expressing the relative importance of a short connection time
latency	An int expressing the relative importance of low latency
bandwidth	An int expressing the relative importance of high bandwidth

protected void shutdownInput ()

Places the input stream for this socket at "end of stream". Any data sent to this socket is acknowledged and then silently discarded. If you read from a socket input stream after invoking this method on the socket, the stream's available method will return 0, and its read methods will return -1 (end of stream).

Throws

IOException	if an I/O error occurs when shutting down this socket.

See Also

• Socket.shutdownOutput()
• Socket.close()
• Socket.setSoLinger(boolean, int)

protected void shutdownOutput ()

Disables the output stream for this socket. For a TCP socket, any previously written data will be sent followed by TCP's normal connection termination sequence. If you write to a socket output stream after invoking shutdownOutput() on the socket, the stream will throw an IOException.

Throws

IOException	if an I/O error occurs when shutting down this socket.

See Also

• Socket.shutdownInput()
• Socket.close()
• Socket.setSoLinger(boolean, int)

protected boolean supportsUrgentData ()

Returns whether or not this SocketImpl supports sending urgent data. By default, false is returned unless the method is overridden in a sub-class

Returns

• true if urgent data supported

See Also

• address