FTP client in Python

This article will show you how to use the File Transfer Protocol (FTP)  with Python from a client side perspective.  We use ftplib, a library that implements the FTP protocol.   Using FTP we can create and access remote files through function calls.

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Directory listing
We can list the root directory using this little snippet:

import ftplib
ftp = ftplib.FTP("ftp.nluug.nl")
ftp.login("anonymous", "ftplib-example-1")
data = []
for line in data:
    print "-", line

This will output the directory contents. in a simple console style output. If you want to show a specific directory you must change the directory after connecting with the ftp.cwd(‘/’) function where the parameter is the directory you want to change to.

import ftplib
ftp = ftplib.FTP("ftp.nluug.nl")
ftp.login("anonymous", "ftplib-example-1")
data = []
ftp.cwd('/pub/')         # change directory to /pub/
for line in data:
    print "-", line

Download file
To download a file we use the retrbinary() function. An example below:

import ftplib
import sys
def getFile(ftp, filename):
        ftp.retrbinary("RETR " + filename ,open(filename, 'wb').write)
        print "Error"
ftp = ftplib.FTP("ftp.nluug.nl")
ftp.login("anonymous", "ftplib-example-1")
ftp.cwd('/pub/')         # change directory to /pub/

Uploading files
We can upload files using the storlines() command.  This will upload the file README.nluug in the main directory. If you want to upload in another directory combine it with the cwd() function.

import ftplib
import os
def upload(ftp, file):
    ext = os.path.splitext(file)[1]
    if ext in (".txt", ".htm", ".html"):
        ftp.storlines("STOR " + file, open(file))
        ftp.storbinary("STOR " + file, open(file, "rb"), 1024)
ftp = ftplib.FTP("")
ftp.login("username", "password")
upload(ftp, "README.nluug")

Other functions
For other functions please refer to the official library documentation.

Building an IRC (ro)bot

There are tons of (ro)bots out there for IRC (Internet Relay Chat). So how do you start and build one in Python, just for fun?

You will need a program that connects with an IRC server and acts like a traditional IRC client.  IRC servers never ask for any type of complicated human verification such as solving captchas, which is why we can simply connect with a script. The script itself will use network sockets,  a library that is often used to provide network interactions in many programming languages including Python and C/C++.

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IRC and Python
To communicate with an IRC server, you need to use the IRC protocol.  The IRC protocol has distinct messages such as PRIVMSG, USER, NICK and JOIN. If you are curious, you could read the entire protocol. But following this tutorial may be a lot simpler 😉 Authentication is achieved using only a few steps:

The IRC protocol is a layer on top of the IP protocol.   To create a socket we use the command:

 irc = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

socket.AF_INET tells the library to use the network protocol IPv4.   The second argument tells the library to use stream sockets, which are traditionally implemented on the TCP protocol. (IRC works over TCP/IP). We then must use the commands to authenticate with the server:

USER botname botname botname: phrase
NICK botname
JOIN #channel

Sometimes the IDENT command is neccesary too. Summing up, we get this class (save it as irc.py):

import socket
import sys
class IRC:
    irc = socket.socket()
    def __init__(self):  
        self.irc = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    def send(self, chan, msg):
        self.irc.send("PRIVMSG " + chan + " " + msg + "n")
    def connect(self, server, channel, botnick):
        #defines the socket
        print "connecting to:"+server
        self.irc.connect((server, 6667))                                                         #connects to the server
        self.irc.send("USER " + botnick + " " + botnick +" " + botnick + " :This is a fun bot!n") #user authentication
        self.irc.send("NICK " + botnick + "n")               
        self.irc.send("JOIN " + channel + "n")        #join the chan
    def get_text(self):
        text=self.irc.recv(2040)  #receive the text
        if text.find('PING') != -1:                      
            self.irc.send('PONG ' + text.split() [1] + 'rn') 
        return text

Now that we have the network connectivity class, we can use it as an instance.  We will keep our (ro)bot simple for explanatory purposes. The bot will reply “Hello!” if it gets the message “hello” in the channel it resides.

from irc import *
import os
import random
channel = "#testit"
server = "irc.freenode.net"
nickname = "reddity"
irc = IRC()
irc.connect(server, channel, nickname)
while 1:
    text = irc.get_text()
    print text
    if "PRIVMSG" in text and channel in text and "hello" in text:
        irc.send(channel, "Hello!")

Save it as bot.py and run with python bot.py. Connect with a traditional irc client (mirc,hexchat,irsii) to the the channel and observe the experiment has worked! You can now extend it with any cool features you can imagine.