Module java.base
Package java.net

# Class DatagramSocketImpl

java.lang.Object
java.net.DatagramSocketImpl

All Implemented Interfaces:
  `SocketOptions`

public abstract class DatagramSocketImpl extends Object implements SocketOptions
Abstract datagram and multicast socket implementation base class.

Implementation Note:
  Sockets created with the `DatagramSocket` and `MulticastSocket` public constructors historically delegated all socket operations to a `DatagramSocketImpl` implementation named "PlainDatagramSocketImpl". `DatagramSocket` and `MulticastSocket` have since been changed to a new implementation based on `DatagramChannel`. The JDK continues to ship with the older implementation to allow code to run that depends on unspecified behavior that differs between the old and new implementations. The old implementation will be used if the Java virtual machine is started with the system property `jdk.net.usePlainDatagramSocketImpl` set to use the old implementation. It may also be set in the JDK's network configuration file, located in `${java.home}/conf/net.properties`. The value of the property is the string representation of a boolean. If set without a value then it defaults to `true`, hence running with `-Djdk.net.usePlainDatagramSocketImpl` or `-Djdk.net.usePlainDatagramSocketImpl=true` will configure the Java virtual machine to use the old implementation. The property and old implementation will be removed in a future version.
Since:
  1.1

## Field Summary

Fields
Modifier and Type
Field
Description
`protected FileDescriptor`
`fd`
The file descriptor object.
`protected int`
`localPort`
The local port number.

### Fields declared in interface java.net.SocketOptions

`IP_MULTICAST_IF, IP_MULTICAST_IF2, IP_MULTICAST_LOOP, IP_TOS, SO_BINDADDR, SO_BROADCAST, SO_KEEPALIVE, SO_LINGER, SO_OOBINLINE, SO_RCVBUF, SO_REUSEADDR, SO_REUSEPORT, SO_SNDBUF, SO_TIMEOUT, TCP_NODELAY`

## Constructor Summary

Constructors
Constructor
Description
`DatagramSocketImpl()`
Constructor for subclasses to call.

## Method Summary

Modifier and Type
Method
Description
`protected abstract void`
`bind(int lport, InetAddress laddr)`
Binds a datagram socket to a local port and address.
`protected abstract void`
`close()`
Close the socket.
`protected void`
`connect(InetAddress address, int port)`
Connects a datagram socket to a remote destination.
`protected abstract void`
`create()`
Creates a datagram socket.
`protected void`
`disconnect()`
Disconnects a datagram socket from its remote destination.
`protected FileDescriptor`
`getFileDescriptor()`
Gets the datagram socket file descriptor.
`protected int`
`getLocalPort()`
Gets the local port.
`protected <T> T`
`getOption(SocketOption<T> name)`
Called to get a socket option.
`protected abstract int`
`getTimeToLive()`
Retrieve the TTL (time-to-live) option.
`protected abstract byte`
`getTTL()`
Deprecated.
use getTimeToLive instead.
`protected abstract void`
`join(InetAddress inetaddr)`
Join the multicast group.
`protected abstract void`
`joinGroup(SocketAddress mcastaddr, NetworkInterface netIf)`
Join the multicast group.
`protected abstract void`
`leave(InetAddress inetaddr)`
Leave the multicast group.
`protected abstract void`
`leaveGroup(SocketAddress mcastaddr, NetworkInterface netIf)`
Leave the multicast group.
`protected abstract int`
`peek(InetAddress i)`
Peek at the packet to see who it is from.
`protected abstract int`
`peekData(DatagramPacket p)`
Peek at the packet to see who it is from.
`protected abstract void`
`receive(DatagramPacket p)`
Receive the datagram packet.
`protected abstract void`
`send(DatagramPacket p)`
Sends a datagram packet.
`protected <T> void`
`setOption(SocketOption<T> name, T value)`
Called to set a socket option.
`protected abstract void`
`setTimeToLive(int ttl)`
Set the TTL (time-to-live) option.
`protected abstract void`
`setTTL(byte ttl)`
Deprecated.
use setTimeToLive instead.
`protected Set<SocketOption<?>>`
`supportedOptions()`
Returns a set of SocketOptions supported by this impl and by this impl's socket (DatagramSocket or MulticastSocket)

### Methods declared in class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

### Methods declared in interface java.net.SocketOptions

`getOption, setOption`

## Field Details

### localPort

protected int localPort
The local port number.

### fd

protected FileDescriptor fd
The file descriptor object.

## Constructor Details

### DatagramSocketImpl

public DatagramSocketImpl()
Constructor for subclasses to call.

## Method Details

### create

protected abstract void create() throws SocketException
Creates a datagram socket.

Throws:
  `SocketException` - if there is an error in the underlying protocol, such as a TCP error.

### bind

protected abstract void bind(int lport, InetAddress laddr) throws SocketException
Binds a datagram socket to a local port and address.

Parameters:
  `lport` - the local port
  `laddr` - the local address
Throws:
  `SocketException` - if there is an error in the underlying protocol, such as a TCP error.

### send

protected abstract void send(DatagramPacket p) throws IOException
Sends a datagram packet. The packet contains the data and the destination address to send the packet to.

Parameters:
  `p` - the packet to be sent.
Throws:
  `IOException` - if an I/O exception occurs while sending the datagram packet.
  `PortUnreachableException` - may be thrown if the socket is connected to a currently unreachable destination. Note, there is no guarantee that the exception will be thrown.

### connect

protected void connect(InetAddress address, int port) throws SocketException
Connects a datagram socket to a remote destination. This associates the remote address with the local socket so that datagrams may only be sent to this destination and received from this destination. This may be overridden to call a native system connect.

If the remote destination to which the socket is connected does not exist, or is otherwise unreachable, and if an ICMP destination unreachable packet has been received for that address, then a subsequent call to send or receive may throw a PortUnreachableException. Note, there is no guarantee that the exception will be thrown.

Parameters:
  `address` - the remote InetAddress to connect to
  `port` - the remote port number
Throws:
  `SocketException` - may be thrown if the socket cannot be connected to the remote destination
Since:
  1.4

### disconnect

protected void disconnect()
Disconnects a datagram socket from its remote destination.

Since:
  1.4

### peek

protected abstract int peek(InetAddress i) throws IOException
Peek at the packet to see who it is from. Updates the specified `InetAddress` to the address which the packet came from.

Parameters:
  `i` - an InetAddress object
Returns:
  the port number which the packet came from.
Throws:
  `IOException` - if an I/O exception occurs
  `PortUnreachableException` - may be thrown if the socket is connected to a currently unreachable destination. Note, there is no guarantee that the exception will be thrown.

### peekData

protected abstract int peekData(DatagramPacket p) throws IOException
Peek at the packet to see who it is from. The data is copied into the specified `DatagramPacket`. The data is returned, but not consumed, so that a subsequent peekData/receive operation will see the same data.

Parameters:
  `p` - the Packet Received.
Returns:
  the port number which the packet came from.
Throws:
  `IOException` - if an I/O exception occurs
  `PortUnreachableException` - may be thrown if the socket is connected to a currently unreachable destination. Note, there is no guarantee that the exception will be thrown.
Since:
  1.4

### receive

protected abstract void receive(DatagramPacket p) throws IOException
Receive the datagram packet.

Parameters:
  `p` - the Packet Received.
Throws:
  `IOException` - if an I/O exception occurs while receiving the datagram packet.
  `PortUnreachableException` - may be thrown if the socket is connected to a currently unreachable destination. Note, there is no guarantee that the exception will be thrown.

### setTTL

@Deprecated protected abstract void setTTL(byte ttl) throws IOException
Deprecated.
use setTimeToLive instead.
Set the TTL (time-to-live) option.

Parameters:
  `ttl` - a byte specifying the TTL value
Throws:
  `IOException` - if an I/O exception occurs while setting the time-to-live option.
See Also:
  - `getTTL()`

### getTTL

@Deprecated protected abstract byte getTTL() throws IOException
Deprecated.
use getTimeToLive instead.
Retrieve the TTL (time-to-live) option.

Returns:
  a byte representing the TTL value
Throws:
  `IOException` - if an I/O exception occurs while retrieving the time-to-live option
See Also:
  - `setTTL(byte)`

### setTimeToLive

protected abstract void setTimeToLive(int ttl) throws IOException
Set the TTL (time-to-live) option.

Parameters:
  `ttl` - an `int` specifying the time-to-live value
Throws:
  `IOException` - if an I/O exception occurs while setting the time-to-live option.
See Also:
  - `getTimeToLive()`

### getTimeToLive

protected abstract int getTimeToLive() throws IOException
Retrieve the TTL (time-to-live) option.

Returns:
  an `int` representing the time-to-live value
Throws:
  `IOException` - if an I/O exception occurs while retrieving the time-to-live option
See Also:
  - `setTimeToLive(int)`

### join

protected abstract void join(InetAddress inetaddr) throws IOException
Join the multicast group.

Parameters:
  `inetaddr` - multicast address to join.
Throws:
  `IOException` - if an I/O exception occurs while joining the multicast group.

### leave

protected abstract void leave(InetAddress inetaddr) throws IOException
Leave the multicast group.

Parameters:
  `inetaddr` - multicast address to leave.
Throws:
  `IOException` - if an I/O exception occurs while leaving the multicast group.

### joinGroup

protected abstract void joinGroup(SocketAddress mcastaddr, NetworkInterface netIf) throws IOException
Join the multicast group.

Parameters:
  `mcastaddr` - address to join.
  `netIf` - specifies the local interface to receive multicast datagram packets
Throws:
  `IOException` - if an I/O exception occurs while joining the multicast group
Since:
  1.4

### leaveGroup

protected abstract void leaveGroup(SocketAddress mcastaddr, NetworkInterface netIf) throws IOException
Leave the multicast group.

Parameters:
  `mcastaddr` - address to leave.
  `netIf` - specified the local interface to leave the group at
Throws:
  `IOException` - if an I/O exception occurs while leaving the multicast group
Since:
  1.4

### close

protected abstract void close()
Close the socket.

### getLocalPort

protected int getLocalPort()
Gets the local port.

Returns:
  an `int` representing the local port value

### getFileDescriptor

protected FileDescriptor getFileDescriptor()
Gets the datagram socket file descriptor.

Returns:
  a `FileDescriptor` object representing the datagram socket file descriptor

### setOption

protected <T> void setOption(SocketOption<T> name, T value) throws IOException
Called to set a socket option.

Implementation Requirements:
  The default implementation of this method first checks that the given socket option `name` is not null, then throws `UnsupportedOperationException`. Subclasses should override this method with an appropriate implementation.
Type Parameters:
  `T` - The type of the socket option value
Parameters:
  `name` - The socket option
  `value` - The value of the socket option. A value of `null` may be valid for some options.
Throws:
  `UnsupportedOperationException` - if the DatagramSocketImpl does not support the option
  `IllegalArgumentException` - if the value is not valid for the option
  `IOException` - if an I/O error occurs, or if the socket is closed
  `NullPointerException` - if name is `null`
Since:
  9

### getOption

protected <T> T getOption(SocketOption<T> name) throws IOException
Called to get a socket option.

Implementation Requirements:
  The default implementation of this method first checks that the given socket option `name` is not null, then throws `UnsupportedOperationException`. Subclasses should override this method with an appropriate implementation.
Type Parameters:
  `T` - The type of the socket option value
Parameters:
  `name` - The socket option
Returns:
  the socket option
Throws:
  `UnsupportedOperationException` - if the DatagramSocketImpl does not support the option
  `IOException` - if an I/O error occurs, or if the socket is closed
  `NullPointerException` - if name is `null`
Since:
  9

### supportedOptions

protected Set<SocketOption<?>> supportedOptions()
Returns a set of SocketOptions supported by this impl and by this impl's socket (DatagramSocket or MulticastSocket)

Implementation Requirements:
  The default implementation of this method returns an empty set. Subclasses should override this method with an appropriate implementation.
Returns:
  a Set of SocketOptions
Since:
  9