The goal is to create simple packages and send them over UDP. First step is to just check correctness of the packets using a java.MD5 checksum at the end of the packet transmission.

// normales Paket
Packet 
    Transmission id (16),
    Sequence Number (32),
    Data (..)
}

// wenn die Sequenz Nummber = null ist (also erste Paket der startenden
// Übertragung)
Packet {
    Transmission id (16),
    Sequence Number (32),
    Max Sequence Number (32),
    File Name (2..2048)
}

// das lezte Paket der Übertragung (wichtig: checksum)
Packet {
    Transmission id (16),
    Sequence Number (32),
    java.MD5 (128)
}

• listen
  general listen on default port 8080: ./PP --listen
  listen on specific port and ip (both optional): ./PP [-p <port>] [--ip <ip_addr>] --listen
  write received files to specific output directory (new dir is created if necessary): ./PP [-o <pathToDir>] --listen
  listen on port and ip and sotre to directory: ./PP [-p <port>] [--ip <ip_addr>] [-o <pathToDir>] --listen
• send
  general send to default ip and port (localhost, 8080): ./PP --send <pathToFile>
  send with ip and port (both optional): ./PP [-p <port>] [--ip <ip_addr>] --send <pathToFile>
  
• verbose
  for verbose output, add -v to the call: ./PP -v --listen