Program 4 - Detect a Person

Due Date - Nov 20, 2023

Objectives

The objective of this assignment is to design and implement a client-server system using Raspberry Pi devices. The server will control an LED, while the client will sense motion using a Passive Infrared Sensor (PIR) and communicate with the server to blink the LED. The assignment includes establishing a three-way handshake, sending blink duration and count information, acknowledging the data, and responding to motion detection by blinking the LED. The client and server communications MUST use UDP (SOCK_DGRAM) and NOT TCP.

The objectives are:

– Learn about physical computing

– Learn about protocol development

Server Specifications

The server (we name it lightserver) takes two arguments:

$ lightserver -p <PORT> -s <LOG FILE LOCATION>

1.PORT - The port server listens on.

2.Log File Location - log file location

Server’s Functional requirements

  1. The server must open a UDP socket on the specified port number
  2. The server should gracefully process incorrect port number and exit with a non-zero error code
  3. The server runs indefinitely - it does not exit.
  4. The server accepts connections from multiple clients (bonus points)
  5. server works with any client developed by other teams (bonus points)

Client Specifications

The client (we name it lightclient) takes three arguments:

$ lightclient -s <SERVER-IP> -p <PORT> -l LOGFILE

The client takes three arguments:

1.Server IP - The IP address of the lightserver.

2.PORT - The port the server listens on.

2.Log file location - Where you will keep a record of packets you received.

For example:
$ lightclient -s 192.168.2.1 -p 6543 -l LOGFILE

Packet Specification

The payload of each UDP packet sent by server and client MUST start with the following 12-byte header. All fields are in network order (most significant bit first):

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                     Sequence Number                           |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                     Acknowledgment Number                     |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                     Not Used                            |A|S|F|
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Where:

  1. Sequence Number (32 bits): If SYN is present (the S flag is set) the sequence number is the initial sequence number (randomly choosen).

  2. Acknowledgement Number (32 bits): If the ACK bit is set, this field contains the value of the next sequence number the sender of the segment is expecting to receive. Once a connection is established this is always sent.

  3. The acknowledgement number is given in the unit of bytes (how many bytes you have sent)

  4. Not Used (29 bits): Must be zero.

  5. A (ACK, 1 bit): Indicates that there the value of Acknowledgment Number field is valid

  6. S (SYN, 1 bit): Synchronize sequence numbers

  7. F (FIN, 1 bit): Finish, No more data from sender

This is the protocol you will implement

  1. The client opens a UDP socket and initiate 3-way handshake to the specified hostname/ip and port. Essentially, the client and server will exchange three packets with the following flags set: (1) SYN (2) SYN|ACK (3)ACK. At the end of the handshake, they will have learned each other’s sequence number.

  2. The client then sends the duration and number of blinks as a payload.

  3. The server acknowledges the duration and the number of blinks.

  4. The client senses motion using the PIR.

  5. When motion is detected, the client logs it, and sends a message with the following string as the payload :MotionDetected

  6. The server parses it, logs :MotionDetected to its log, and drives the LED for the pre-determined amount of times.

  7. Client sends a packet with the FIN bit set. The server logs “:Interaction with completed. This finishes the interaction.

  8. Timestamp format is “YYYY-MM-DD-HH-MM-SS”.

Hardware Components

  • Raspberry Pi
  • Passive Infrared Sensor (PIR)
  • LED
  • Resistor
  • Jumper wires
  • Breadboard

Server Setup

  • The server Raspberry Pi should be programmed to drive the LED.
  • It should be capable of receiving data from the client and blinking the LED accordingly.

Client Setup

  • The client Raspberry Pi should be programmed to interface with the PIR sensor.
  • It should be able to establish a connection with the server.
  • The client should continuously sense motion using the PIR sensor.

You may test both server and client on the same board.

Submission:

  1. Submit your code, packet capture in PCAP format, and your logs as a ZIP file.

Additional requirements:

  1. Code must compile/run on the PIs.

  2. For each packet received, log both at server and receiver in the following format:

"RECV" <Sequence Number> <Acknowledgement Number> ["ACK"] ["SYN"] ["FIN"]
"SEND" <Sequence Number> <Acknowledgement Number> ["ACK"] ["SYN"] ["FIN"]

Hints

def create_packet(**kwargs):

data = struct.pack('!I', s_n) #pack the version
....
data += struct.pack("!c", ack) #pack the ACK
data += struct.pack("!c", syn) #pack the SYN
data += struct.pack("!c", fin) #pack the FIN
....
return data

send_data = create_packet(sequence_number=100, ack_number=0, ack = 'Y', syn = 'N', fin = 'N', payload=data)

Rubric

  • Protocol design points 1-7 - 10 points each.
  • Successful reading from PIR - 10 points.
  • Successful LED blinking - 10 points.
  • Server can handle multiple clients - 10 points (bonus)
  • Works with other teams’ implementation - 10 points (bonus)
    • Do not collaborate on code but test with each other’s code
    • If your code works with another team’s code, you both get 10 points
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