de.tubs.macs.util.net
Class DDH

java.lang.Object
  |
  +--java.lang.Thread
        |
        +--de.tubs.macs.util.net.DDH

public class DDH

extends java.lang.Thread

implements Net

DDH - Dirks Dirty Hack A simple UDP based protocol providing segmentated semi-reliable transmission of data between TWO partners. a low level DDH Packet has a 4 byte header 0 sequence number high byte 1 sequence number low byte 2 number of current segment 3 total number of segments a resend request will set total to 0 and the seqence number will reflect the requested packet. the algorithm is very simple. if a missing segment is detected the whole corresponding object is requested again. this will occure only once, that is if packets from the same object are lost again it will be ignored! To improve this the following has to be done! 1. make a list of remote sites and move all relevant data into such an entry -> cleaner design -> easier extension to multiparty (not just one communication partner) 2. move DDHBuffer and Co to seperate files -> better modularity 3. change buffer strategy by replacing oldest entries and not just first -> better recovery 4. introduce retry counter to allow variable number of retries -> better recovery and felxibility 5. introduce remote hardbeat (including sequence number) -> faster repair -> enable detection of loss of contact -> allows to flush buffer and to stop sending 6. enable multiparty support

Author:

D. Sturzebecher

Inner Class Summary

class	DDH.DDHBuffer
class	DDH.DDHBufferEntry

Field Summary

static java.lang.String	name
static DDH	primary

Fields inherited from class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY, values

Constructor Summary

DDH(java.lang.String typeID, NetManager netManager)

Method Summary

void	close() Close the connections.
void	flush() Flush the send Queue (if applicable).
NetAddress	getAddress() Get address.
DDHAddress	getLocalAddress()
java.lang.Object	getOptions() Get options.
DDHAddress	getRemoteAddress()
int	getTTL() return the scope of the Network in form of a TTL.
java.lang.String	getType() return the type id of the Network
void	init(NetReceiver receiver, NetAddress otherAddress) Initialise the system and set the receiver for data.
void	run() process incoming packets
boolean	send(java.lang.Object object) Send a Object and return its size in byte.
boolean	setRemoteAddress(java.net.InetAddress address, int port, long seq) Set remote address.

Methods inherited from class java.lang.Thread

, activeCount, checkAccess, countStackFrames, currentThread, destroy, dumpStack, enumerate, getContextClassLoader, getName, getPriority, getThreadGroup, interrupt, interrupted, isAlive, isDaemon, isInterrupted, join, join, join, resume, setContextClassLoader, setDaemon, setName, setPriority, sleep, sleep, start, stop, stop, suspend, toString, yield

Methods inherited from class java.lang.Object

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

Field Detail

name

public static final java.lang.String name

primary

public static DDH primary

Constructor Detail

DDH

public DDH(java.lang.String typeID,
           NetManager netManager)

Method Detail

getType

public java.lang.String getType()

Description copied from interface: Net

return the type id of the Network

Specified by:

getType in interface Net

getTTL

public int getTTL()

Description copied from interface: Net

return the scope of the Network in form of a TTL. This should be replaced by a better mechanism sometime.

Specified by:

getTTL in interface Net

getLocalAddress

public DDHAddress getLocalAddress()

getRemoteAddress

public DDHAddress getRemoteAddress()

init

public void init(NetReceiver receiver,
                 NetAddress otherAddress)
          throws NetException

Initialise the system and set the receiver for data.

This should only be used by the NetManager !

Specified by:

init in interface Net

Parameters:

receiver - NetReciever

group - address of the net group

Throws:

NetException - see NetException doc for detail

run

public void run()

process incoming packets

Overrides:

run in class java.lang.Thread

send

public boolean send(java.lang.Object object)
             throws NetException

Send a Object and return its size in byte.

Specified by:

send in interface Net

Throws:

NetException - see NetException doc for detail

getAddress

public NetAddress getAddress()
                      throws NetException

Get address.

Specified by:

getAddress in interface Net

Throws:

NetException - see NetException doc for detail

setRemoteAddress

public boolean setRemoteAddress(java.net.InetAddress address,
                                int port,
                                long seq)
                         throws java.io.IOException

Set remote address.

Throws:

NetException - see NetException doc for detail

getOptions

public java.lang.Object getOptions()

Get options.

Specified by:

getOptions in interface Net

Throws:

NetException - see NetException doc for detail

flush

public void flush()
           throws NetException

Flush the send Queue (if applicable).

Specified by:

flush in interface Net

Throws:

NetException - see NetException doc for detail

close

public void close()
           throws NetException

Close the connections.

Specified by:

close in interface Net

Throws:

NetException - see NetException doc for detail