/AirPiComm

AirPiComm is a project that enables Bluetooth and TCP/IP communication between devices using simple client-server architecture. It includes C programs for data transmission and scripts to automate network setup, making it easy to establish and manage connections in ad-hoc networks.

Primary LanguageCMIT LicenseMIT

Project Report

Floréal Risso and Alexis Paronnaud
SECIL

Table of Contents

  1. Program Explanation
  2. Demonstration

Program Explanation

Sender

The Sender software consists of two executables: a client and a server.

Server

The server can be started with several parameters, depending on the mode—TCP/IP or Bluetooth.

  • Bluetooth Mode: The server requires a channel for communication, the maximum number of simultaneous connections, and optionally, a flag to enable logging in the console.
  • TCP/IP Mode: The server requires a port number, the maximum number of simultaneous connections, and optionally, a flag to enable logging. The server will listen on the specified port indefinitely.

Usage:

Usage: server <MODE> <port/channel> <max_client> [-l]
-l :  enable logging
MODE:
  -b :  bluetooth
  -i :  ip

Examples:

# Start the server in TCP/IP mode on port 9999, allowing up to 1 client, with logging enabled.
server -i 9999 1 -l

# Start the server in TCP/IP mode on port 19191, allowing up to 1000 clients.
server -i 19191 1000

# Start the server in Bluetooth mode on channel 10, allowing up to 1 client, with logging enabled.
server -b 10 1 -l

# Start the server in Bluetooth mode on channel 1, allowing up to 8 clients.
server -b 1 8

Client

The client can be started with several parameters, depending on the mode—TCP/IP or Bluetooth.

  • Bluetooth Mode: The client requires a Bluetooth MAC address, a channel, a list of actions, and optionally, a flag to enable logging.
  • TCP/IP Mode: The client requires an IP address, a port number, a list of actions, and optionally, a flag to enable logging.

Actions can include sending a list of files or executing a command on the target machine.

Usage:

Usage: client MODE <addr> <port/channel> [-f <file>] [-c <command>] [-l]
-l :  enable logging
MODE:
  -b : bluetooth
  -i : ip

Examples:

# Send files f1.txt, f2.txt, and f3.txt over Bluetooth to the address AA:AA:AA:AA on channel 1 with logging enabled.
client -b AA:AA:AA:AA 1 -f f1.txt f2.txt f3.txt -l

# Send file f1.txt over Bluetooth to the address AA:AA:AA:AA on channel 1.
client -b AA:AA:AA:AA 1 -f f1.txt

# Execute the command `ls` on the machine with the Bluetooth address AA:AA:AA:AA via channel 1.
client -b AA:AA:AA:AA 1 -c ls

# Send files f1.txt, f2.txt, and f3.txt over TCP/IP to the address 127.0.0.1 on port 10000 with logging enabled.
client -i 127.0.0.1 10000 -f f1.txt f2.txt f3.txt -l

# Send file f1.txt over TCP/IP to the address 127.0.0.1 on port 10000.
client -i 127.0.0.1 10000 -f f1.txt

# Execute the command `ls` on the machine with IP address 127.0.0.1 via port 10000.
client -i 127.0.0.1 10000 -c ls

Scripts

To automate several tasks, particularly setting up the networks, we have developed the following scripts:

  • bestchan.sh: Identifies the least-used Wi-Fi channel among nearby stations.

    $ ./bestchan.sh
1

  • essid2chan.sh: Identifies the channel used by a specific station.

    $ ./essid2chan.sh <essid>
$ ./essid2chan.sh Flalexis
2

  • wsetup-server.sh: Sets up an ad-hoc Wi-Fi network (server-side).

    $ sudo ./wsetup-server.sh 192.168.15.40

  • wsetup-client.sh: Sets up an ad-hoc Wi-Fi network (client-side).

    $ sudo ./wsetup-client.sh 192.168.15.41

  • bsetup-client.sh: Pairs devices over Bluetooth. The Bluetooth MAC address can be set via the BADDR environment variable.

  • bsetup-server.sh: Pairs devices over Bluetooth.

  • breset.sh: Resets Bluetooth settings and removes a paired device. The Bluetooth MAC address can be set via the BADDR environment variable.

We also developed a script, ishell.sh, which sets up a reverse shell using netcat. This script provides a simple solution for the second part of the lab exercise:

On the server side:

$ ./ishell.sh

On the client side, connect to the server, which gives access to an interactive shell:

$ nc 192.168.15.41 6000
pwd
/home/pi/tp_rsf
whoami
pi
...

Demonstration

This demonstration scenario involves Raspberry Pi A (rA), an embedded system (e.g., a surveillance camera), and Raspberry Pi B (rB), a control device.

We assume that the script configuring the ad-hoc network automatically runs on rA at startup, along with the Sender server in TCP/IP mode.

Wi-Fi Setup

Server

The wsetup-server.sh script automatically runs on the server at startup, setting up an ad-hoc network on the least congested channel, determined by the bestchan.sh script.

$ sudo ./wsetup-server.sh 192.168.15.41
ip: 192.168.15.41, chan: 2

Client

Meanwhile, on the client side, the user runs the wsetup-client.sh script, which detects the channel corresponding to the ESSID and configures the network interface accordingly.

$ sudo ./wsetup-client.sh 192.168.15.40
ip: 192.168.15.40, chan: 2

Bluetooth Setup and Data Exchange

Data Exchange via Wi-Fi

After the Wi-Fi setup, the server automatically starts the sender/server in TCP/IP mode, allowing remote interaction without physical access to the machine.

$ ./sender/server -i 9999 10 -l
[1906] Waiting for a new client

The client then starts the sender/client program in TCP/IP mode and uses it to send the Bluetooth setup script (bsetup-server.sh) to the server.

$ ./sender/client -i 192.168.15.41 9999 -f bsetup-server.sh

The server logs will reflect the file transfer:

[1907] Waiting for a new job
[1907] Downloading a file...
[1907] Create : tmp/tmp_1644611798.out
[1907] Receiving file...
[1907] File received
[1907] Waiting for a new job
[1907] The connection has been closed

Bluetooth Setup

To establish the Bluetooth connection, the client retrieves the server's Bluetooth MAC address and executes the setup script on the server.

# Retrieve the server's Bluetooth MAC address.
bmac=$(
  sender/client -i 192.168.15.41 9999 \
    -c 'bluetoothctl show | head -n 1' |
    tail -n 1 |
    cut -d ' ' -f 2
)

# Execute the Bluetooth setup script on the server.
sender/client -i 192.168.15.41 9999 -c 'sh tmp/$(ls -t tmp | head -n 1)'

# Execute the Bluetooth setup script on the client.
BADDR=$bmac ./bsetup-client

The server logs show the executed commands:

[1908] Waiting for a new job
[1908] Executing a command
[1908] $ sh bmac=$(sender/client -i 192.168.15.41 9999 \
    -c 'bluetoothctl show | head -n 1' | tail -n 1 | cut -d ' ' -f 2)
[1908] Waiting for a new job
[1908] The connection has been closed
[1909] Waiting for a new job
[1909] Executing a command
[1909] $ sh tmp/$(ls -t tmp | head -n 1)
[1909] Waiting for a new job
[1909] The connection has been closed

Now both machines are connected via Bluetooth.

Data Exchange via Bluetooth

With the Bluetooth connection established, the sender/server is started in Bluetooth mode.

$ sender/client -i 192.168.15.41 9999 -c 'sender/server -b 1 -l'

From this point forward, all communication can be done over Bluetooth. For example, you can run the classic "Hello, World!" command via Bluetooth:

$ sender/client -b 1 1 -c 'echo "Hello, world!"'
Hello, world!