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UDP Chat - Android App

P2P Chat app:

• Discovering other users on local network
• Username
• Sending datagrams of chosen size
• Setting sending port
• Timeout

Multithreading

Application uses 4 threads:

• Main thread
• For Sending UDP Datagram
• For Receiving UDP Datagram
• For handling Timeout

UDPSender

Contains list of sending tasks

Waits (sleeps) if list is empty

Other threads put tasks into list via MainActivity. Thread if notified (waked up) if new task is added.

UDPReceiver

Waits for incoming Datagram and process it

UDPTimeout

Sleeps given time, than checks if confirmation message has been received for all Messages, if not re-sends message otherwise removes the message from list.

Protocol

• 1st byte represents type of message
  • 0 = Discovery
  • 1 = Message
  • 2 = Confirmation
  • 3 = Re-name
• 2nd to 5th bytes represents serial number of dataram
• 6th to 9th bytes represents total count of datagrams in series
• other bytes represents metadata or content (depending on type of message)

Metadata

• Discovery
  • 10th byte 0 for request, 1 for response
• Message
  • 10th to 13th bytes - id of message
• Confirmation
  • 10th to 13th bytes - id of message

Class Structure