Class Receiver

java.lang.Object

Receiver

public class Receiver
extends java.lang.Object

The main class. It simulates a application (image viewer) receiver by maintaining a list buffer. It collects packets from the queue of InputDriver and arrange them properly, and then reconstructs the image file from its list buffer.

Constructor Summary

Constructors

Constructor and Description
Receiver(java.lang.String file) Constructs a Receiver to obtain the image file transmitted.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	askForMissingPacket(int seq) Asks for retransmitting the packet with a sequence number.
SimplePacket	askForNextPacket() Returns the next packet.
boolean	askForRetransmit(SimplePacket pkt) Asks for retransmitting the packet.
void	displayList() Outputs the formatted content in the PacketLinkedList buffer.
PacketLinkedList<SimplePacket>	getListBuffer() Returns the PacketLinkedList buffer in the receiver
static void	main(java.lang.String[] args) Initiates a Receiver to reconstruct collected packets and open the Image file, which is specified by args[0].
void	openImage() Opens the image file by merging the content in the maintained list buffer.
void	reconstructFile() Reconstructs the file by arranging the PacketLinkedList in correct order.
boolean	validImageContent() Returns true if the maintained list buffer has a valid image content.
boolean	validImageHeader() Returns if the maintained list buffer has a valid image header

Methods inherited from class java.lang.Object

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

Constructor Detail

Receiver

public Receiver(java.lang.String file)

Constructs a Receiver to obtain the image file transmitted.

Parameters:

file - the filename you want to receive

Method Detail

getListBuffer

public PacketLinkedList<SimplePacket> getListBuffer()

Returns the PacketLinkedList buffer in the receiver

Returns:

the PacketLinkedList object

askForRetransmit

public boolean askForRetransmit(SimplePacket pkt)

Asks for retransmitting the packet. The new packet with the sequence number will arrive later by using askForNextPacket(). Notice that ONLY packet with invalid checksum will be retransmitted.

Parameters:

pkt - the packet with bad checksum

Returns:

true if the requested packet is added in the receiving queue; otherwise, false

askForMissingPacket

public boolean askForMissingPacket(int seq)

Asks for retransmitting the packet with a sequence number. The requested packet will arrive later by using askForNextPacket(). Notice that ONLY missing packet will be retransmitted. Pass seq=0 if the missing packet is the "End of Streaming Notification" packet.

Parameters:

seq - the sequence number of the requested missing packet

Returns:

true if the requested packet is added in the receiving queue; otherwise, false

askForNextPacket

public SimplePacket askForNextPacket()

Returns the next packet.

Returns:

the next SimplePacket object; returns null if no more packet to receive

validImageContent

public boolean validImageContent()

Returns true if the maintained list buffer has a valid image content. Notice that when it returns false, the image buffer could either has a bad header, or just bad body, or both.

Returns:

true if the maintained list buffer has a valid image content; otherwise, false

validImageHeader

public boolean validImageHeader()

Returns if the maintained list buffer has a valid image header

Returns:

true if the maintained list buffer has a valid image header; otherwise, false

displayList

public void displayList()

Outputs the formatted content in the PacketLinkedList buffer. See course webpage for the formatting detail.

reconstructFile

public void reconstructFile()

Reconstructs the file by arranging the PacketLinkedList in correct order. It uses askForNextPacket() to get packets until no more packet to receive. It eliminates the duplicate packets and asks for retransmitting when getting a packet with invalid checksum.

openImage

public void openImage()

Opens the image file by merging the content in the maintained list buffer.

Throws:

BadImageHeaderException - if the maintained list buffer has an invalid image header

BadImageContentException - if the maintained list buffer has an invalid image content

main

public static void main(java.lang.String[] args)

Initiates a Receiver to reconstruct collected packets and open the Image file, which is specified by args[0].

Parameters:

args - command line arguments