org.jgroups.protocols

Class UDP

Implemented Interfaces:
Runnable

public class UDP
extends Protocol
implements Runnable

IP multicast transport based on UDP. Messages to the group (msg.dest == null) will be multicast (to all group members), whereas point-to-point messages (msg.dest != null) will be unicast to a single member. Uses a multicast and a unicast socket.

The following properties are being read by the UDP protocol

param mcast_addr - the multicast address to use default is 228.8.8.8
param mcast_port - (int) the port that the multicast is sent on default is 7600
param ip_mcast - (boolean) flag whether to use IP multicast - default is true
param ip_ttl - Set the default time-to-live for multicast packets sent out on this socket. default is 32
param use_packet_handler - If set, the mcast and ucast receiver threads just put the datagram's payload (a byte buffer) into a queue, from where a separate thread will dequeue and handle them (unmarshal and pass up). This frees the receiver threads from having to do message unmarshalling; this time can now be spent receiving packets. If you have lots of retransmissions because of network input buffer overflow, consider setting this property to true (default is false).

Author:
Bela Ban

Nested Class Summary

class
UDP.UcastReceiver

Field Summary

Fields inherited from class org.jgroups.stack.Protocol

down_handler, down_prot, down_queue, down_thread, down_thread_prio, log, observer, props, stack, up_handler, up_prot, up_queue, up_thread, up_thread_prio

Constructor Summary

UDP()
public constructor.

Method Summary

void
down(Event evt)
Caller by the layer above this layer.
String
getName()
void
init()
Called after instance has been created (null constructor) and before protocol is started.
void
run()
boolean
setProperties(Properties props)
Setup the Protocol instance acording to the configuration string The following properties are being read by the UDP protocol param mcast_addr - the multicast address to use default is 228.8.8.8 param mcast_port - (int) the port that the multicast is sent on default is 7600 param ip_mcast - (boolean) flag whether to use IP multicast - default is true param ip_ttl - Set the default time-to-live for multicast packets sent out on this socket.
void
start()
Creates the unicast and multicast sockets and starts the unicast and multicast receiver threads
void
startUpHandler()
DON'T REMOVE ! This prevents the up-handler thread to be created, which essentially is superfluous: messages are received from the network rather than from a layer below.
void
stop()
This method is called on a Channel.disconnect().
String
toString()
debug only
void
up(Event evt)
handle the UP event.

Methods inherited from class org.jgroups.stack.Protocol

destroy, down, getDownProtocol, getDownQueue, getName, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, init, passDown, passUp, providedDownServices, providedUpServices, receiveDownEvent, receiveUpEvent, requiredDownServices, requiredUpServices, setDownProtocol, setObserver, setProperties, setPropertiesInternal, setProtocolStack, setUpProtocol, start, startDownHandler, startUpHandler, stop, stopInternal, up

Constructor Details

UDP

public UDP()
public constructor. creates the UDP protocol, and initializes the state variables, does however not start any sockets or threads

Method Details

down

public void down(Event evt)
Caller by the layer above this layer. Usually we just put this Message into the send queue and let one or more worker threads handle it. A worker thread then removes the Message from the send queue, performs a conversion and adds the modified Message to the send queue of the layer below it, by calling Down).
Overrides:
down in interface Protocol

getName

public String getName()
Overrides:
getName in interface Protocol

init

public void init()
            throws Exception
Called after instance has been created (null constructor) and before protocol is started. Properties are already set. Other protocols are not yet connected and events cannot yet be sent.
Overrides:
init in interface Protocol

run

public void run()

setProperties

public boolean setProperties(Properties props)
Setup the Protocol instance acording to the configuration string The following properties are being read by the UDP protocol param mcast_addr - the multicast address to use default is 228.8.8.8 param mcast_port - (int) the port that the multicast is sent on default is 7600 param ip_mcast - (boolean) flag whether to use IP multicast - default is true param ip_ttl - Set the default time-to-live for multicast packets sent out on this socket. default is 32
Overrides:
setProperties in interface Protocol
Returns:
true if no other properties are left. false if the properties still have data in them, ie , properties are left over and not handled by the protocol stack

start

public void start()
            throws Exception
Creates the unicast and multicast sockets and starts the unicast and multicast receiver threads
Overrides:
start in interface Protocol

startUpHandler

public void startUpHandler()
DON'T REMOVE ! This prevents the up-handler thread to be created, which essentially is superfluous: messages are received from the network rather than from a layer below.
Overrides:
startUpHandler in interface Protocol

stop

public void stop()
This method is called on a Channel.disconnect(). Stops work (e.g. by closing multicast socket). Will be called from top to bottom. This means that at the time of the method invocation the neighbor protocol below is still working. This method will replace the STOP, STOP_OK, CLEANUP and CLEANUP_OK events. The ProtocolStack guarantees that when this method is called all messages in the down queue will have been flushed
Overrides:
stop in interface Protocol

toString

public String toString()
debug only

up

public void up(Event evt)
handle the UP event.
Overrides:
up in interface Protocol
Parameters:
evt - - the event being send from the stack

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