Added in API level 1

Summary: Inherited Constants | Fields | Ctors | Methods | Protected Methods | Inherited Methods

SocketImpl

public abstract class SocketImpl
extends Object implements SocketOptions

java.lang.Object
↳	java.net.SocketImpl

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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.

Summary

Inherited constants

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_REUSEPORT Sets SO_REUSEPORT 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.

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
SocketImpl()

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

Protected methods
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.
<T> T	getOption(SocketOption<T> name) Called to get a socket option.
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.
<T> void	setOption(SocketOption<T> name, T value) Called to set a socket option.
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.
Set<SocketOption<?>>	supportedOptions() Returns a set of SocketOptions supported by this impl and by this impl's socket (Socket or ServerSocket)
boolean	supportsUrgentData() Returns whether or not this SocketImpl supports sending urgent data.

Inherited methods
From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. final Class<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
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

address

Added in API level 1

protected InetAddress address

The IP address of the remote end of this socket.

fd

Added in API level 1

protected FileDescriptor fd

The file descriptor object for this socket.

localport

Added in API level 1

protected int localport

The local port number to which this socket is connected.

port

Added in API level 1

protected int port

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

Public constructors

SocketImpl

Added in API level 1

public SocketImpl ()

Public methods

toString

Added in API level 1

public String toString ()

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

Returns
String	a string representation of this socket.

Protected methods

accept

Added in API level 1

protected abstract void accept (SocketImpl s)

Accepts a connection.

Parameters
s	SocketImpl: the accepted connection.

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

available

Added in API level 1

protected abstract int available ()

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

Returns
int	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.

bind

Added in API level 1

protected abstract void bind (InetAddress host, 
                int port)

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

Parameters
host	InetAddress: an IP address that belongs to a local interface.
port	int: the port number.

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

close

Added in API level 1

protected abstract void close ()

Closes this socket.

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

connect

Added in API level 1

protected abstract void connect (InetAddress address, 
                int port)

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

Parameters
address	InetAddress: the IP address of the remote host.
port	int: the port number.

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

connect

Added in API level 1

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

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

connect

Added in API level 1

protected abstract void connect (String host, 
                int port)

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

Parameters
host	String: the name of the remote host.
port	int: the port number.

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

create

Added in API level 1

protected abstract void create (boolean stream)

Creates either a stream or a datagram socket.

Parameters
stream	boolean: if true, create a stream socket; otherwise, create a datagram socket.

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

getFileDescriptor

Added in API level 1

protected FileDescriptor getFileDescriptor ()

Returns the value of this socket's fd field.

Returns
FileDescriptor	the value of this socket's fd field.

See also:

• fd

getInetAddress

Added in API level 1

protected InetAddress getInetAddress ()

Returns the value of this socket's address field.

Returns
InetAddress	the value of this socket's address field.

See also:

• address

getInputStream

Added in API level 1

protected abstract InputStream getInputStream ()

Returns an input stream for this socket.

Returns
InputStream	a stream for reading from this socket.

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

getLocalPort

Added in API level 1

protected int getLocalPort ()

Returns the value of this socket's localport field.

Returns
int	the value of this socket's localport field.

See also:

• localport

getOption

Added in API level 33

protected T getOption (SocketOption<T> name)

Called to get a socket option.

Parameters
name	SocketOption: The socket option

Returns
T	the value of the named option

Throws
UnsupportedOperationException	if the SocketImpl does not support the option.
IOException	if an I/O error occurs, or if the socket is closed.

getOutputStream

Added in API level 1

protected abstract OutputStream getOutputStream ()

Returns an output stream for this socket.

Returns
OutputStream	an output stream for writing to this socket.

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

getPort

Added in API level 1

protected int getPort ()

Returns the value of this socket's port field.

Returns
int	the value of this socket's port field.

See also:

• port

listen

Added in API level 1

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	int: the maximum length of the queue.

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

sendUrgentData

Added in API level 1

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	int: The byte of data to send

Throws
IOException	if there is an error sending the data.

setOption

Added in API level 33

protected void setOption (SocketOption<T> name, 
                T value)

Called to set a socket option.

Parameters
name	SocketOption: The socket option
value	T: The value of the socket option. A value of null may be valid for some options.

Throws
UnsupportedOperationException	if the SocketImpl does not support the option
IOException	if an I/O error occurs, or if the socket is closed.

setPerformancePreferences

Added in API level 1

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 sub-class.

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

shutdownInput

Added in API level 1

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)

shutdownOutput

Added in API level 1

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)

supportedOptions

Added in API level 33

protected Set<SocketOption<?>> supportedOptions ()

Returns a set of SocketOptions supported by this impl and by this impl's socket (Socket or ServerSocket)

Returns
Set<SocketOption<?>>	a Set of SocketOptions

supportsUrgentData

Added in API level 1

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
boolean	true if urgent data supported

See also:

• address