🛡️ TwoWaySSLTransfer

A simple, secure, and cross-platform Python application for two-way file transfer and text processing using sockets and SSL/TLS.

This project demonstrates a client-server architecture where:

• The Client sends a text file (send.txt) to the Server.
• The Server receives the file, counts the frequency of each word, and saves the results.
• The Client can then request the processed file, which the Server sends back.
• All communication is encrypted.

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How It Works (Protocol Flow)

Client                             Server
  |                                  |
  |--- SSL/TLS Handshake ----------> |
  |                                  |
  |--- Send File Size (8 bytes) ---> |
  |--- Send File Data (send.txt) --> |
  |                                  |
  |                                  | <--- Receive & Process File
  |                                  | <--- Save result_for_client.txt
  |                                  |
  |--- Send 'start' command ----->   |
  |                                  |
  | <--- Send File Size (8 bytes) ---|
  | <--- Send File Data (result) ----|
  |                                  |
  |--- Receive & Save result_file.txt|

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Features

• Secure — All data encrypted with SSL/TLS.
• Two-Way Transfer — Client-to-server and server-to-client communication.
• Simple Protocol — [8-byte file size] + [file data] structure.
• Cross-Platform — Tested between macOS (Client) and Windows (Server).

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Requirements

• Python 3.x
• Standard libraries: socket, ssl, os, collections
• OpenSSL (for generating certificates)

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etup & Installation

1. Clone the Repository

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2. Generate Security Certificates

Run this command in your project directory:

openssl req -x509 -newkey rsa:2048 -nodes -keyout server.key -out server.crt -days 365

This creates two files:

• server.key — your private key
• server.crt — your public certificate

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3. Prepare the Client File

Ensure your send.txt file exists in the project folder and ends with a space and a period ( .) for accurate word counting.

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How to Run

You can run this in two modes:

1. Localhost (Single Machine)
2. Network Mode (Different Machines)

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Localhost Test (Single Machine)

Step 1: Edit client.py

HOST = 'localhost'

Step 2: Start the Server

python3 server.py

Expected output:

Secure server listening on 0.0.0.0:5000...

Step 3: Run the Client

python3 client.py

Type start and press Enter when prompted.

Step 4: Check Results

You’ll find a new file:

client_result.txt

containing the word frequency output.

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🌐 Network Test (Two Machines: macOS Client / Windows Server)

On the Server (Windows)

1. Find IP Address

   ipconfig

   Example: IPv4 Address. . . . . . . . . . . : 172.20.10.9

2. Edit server.py

   HOST = '0.0.0.0'

3. Allow Through Firewall

   • Open Windows Defender Firewall with Advanced Security (wf.msc).
   • Create Inbound Rules:

Rule 1 — Python Port 5000:

• Type: Port → TCP → Port 5000
• Action: Allow the connection
• Profile: Domain, Private, Public
• Name: Python App Port 5000

Rule 2 — Allow Ping (for Testing):

• Type: Custom → Protocol: ICMPv4 → Echo Request
• Action: Allow connection
• Profile: Domain, Private, Public
• Name: Allow All Ping (ICMPv4-In)

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On the Client (macOS)

1. Copy Certificate
   Copy server.crt from the Windows machine to the client project folder.

2. Edit client.py

   HOST = '173.20.10.8'  # Replace with your actual server IP

3. Test Connectivity

   ping 173.20.10.8

   If you get replies, connection is successful.

4. Run Client

   python3 client.py

   Type start and press Enter.

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License

This project is licensed under the MIT License.
See the LICENSE file for details.