Python Project Guide: Build an FTP Client & Server

Network programming is an exciting field, and this guide will show you how to build an FTP client and server in Python 3. The File Transfer Protocol (FTP) is a simple and widely understood protocol, making it a perfect starting point for creating your own network code. We will use Python’s built-in ftplib for the client and the powerful pyftpdlib library for the server.

💻 Understanding the FTP Protocol

FTP is a network protocol used to transfer files between a client and a server. A key disadvantage is that it uses unencrypted traffic, so data is sent in plain text. Many public FTP servers allow ‘Anonymous FTP’ access, where you can log in with the username `anonymous` and your email as the password.

💻 Building an FTP Client with `ftplib`

Python’s standard library includes ftplib, which makes creating an FTP client straightforward.

1. Import and Connect:

   from ftplib import FTP
   
   connection = FTP('ftp.ntua.gr') # Connect to the server

2. Login and List Files:

   connection.login("anonymous", "[email protected]")
   files = connection.nlst() # Get a list of files
   print(files)

3. Download a File: The retrbinary method is used to retrieve a file in binary mode.

   # Open a local file to write to
   localfile = open('index.txt', 'wb')
   # Download the file
   connection.retrbinary('RETR 00_index.txt', localfile.write, 1024)
   localfile.close()

4. Close the Connection:
   connection.close()

💻 Creating an FTP Server with `pyftpdlib`

The `pyftpdlib` library makes it incredibly easy to create a robust, high-performance FTP server.

1. Install the Library:
   pip3 install pyftpdlib
2. Create the Server Script:

   from pyftpdlib.authorizers import DummyAuthorizer
   from pyftpdlib.handlers import FTPHandler
   from pyftpdlib.servers import FTPServer
   
   # Setup users and permissions
   auth = DummyAuthorizer()
   auth.add_user('LXF', 'aPassword12345', '.', perm='elradfmwM')
   auth.add_anonymous('.')
   
   handler = FTPHandler
   handler.authorizer = auth
   handler.banner = "A simple FTP server."
   
   # Start the server
   server = FTPServer(('0.0.0.0', 1234), handler)
   server.serve_forever()

This script sets up a fully functional FTP server on port 1234 with a regular user and anonymous access, ready to accept connections from your client.

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💻 Continue Your Learning Journey

• Python Project Guide: How to Get Started with Python 3
• Python Project Guide: Using Functions in Python 3
• Python Project Guide: Making Scripts
• Python Project Guide: Times, Dates & Numbers
• Python Project Guide: NumPy & SciPy: For Science!

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