deadsimple IRC client in 55 lines of python to show you that IRC is easy to implement - public domain - see also: http://www.faqs.org/rfcs/rfc1459.html

dsirc.py

from sys import stdin
import socket, select

channel = '#worldchat'
server = ('vienna.irc.at',6669)
ident = nick = 'herbert'
user = 'Herbert Herbert'

irc = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
irc.connect(server)
def send(msg): irc.send(bytes(msg, 'utf-8'))

send('NICK %s\r\n' % nick)
send('USER %s 0 0 :%s\r\n' % (ident, user))
send('JOIN %s\r\n' % channel)

poll = select.poll()
poll.register(irc, select.POLLIN)
poll.register(stdin, select.POLLIN)

def do_irc(irc):
	for line in str(irc.recv(2048), 'utf-8').splitlines(): # FIXME check if message ends with \r\n, buffer it otherwise
		sp = line.split(' ')
		if len(sp) > 1 and sp[0].upper() == 'PING':
			send('PONG %s\r\n' % sp[1])
		elif len(sp) > 1 and sp[1].upper() == 'PRIVMSG':
			msg = line.split(':',2)[-1]
			nick = sp[0].split('!')[0].lstrip(':')
			who = nick + (sp[2].lower() != channel.lower() and ':' + sp[2] or '')
			if not msg.startswith('\001'):
				print('<%s> %s' % (who ,msg))
			else: # CTCP
				(ctcp, msg) = msg.strip('\001').split(' ',1)
				if ctcp.upper() == 'ACTION':
					print('* %s %s' % (who, msg))
				else:
					print('! %s requested unknown CTCP %s %s' % (who, ctcp, msg))
		else:
			print(line)

def do_stdin(stdin, irc):
	line = stdin.readline().splitlines()[0]
	if line.startswith('/'):
		send(line[1:] + '\r\n')
	else:
		send('PRIVMSG %s :%s\r\n' % (channel, line))

while True:
	ready = poll.poll()
	for (fd, events) in ready:
		if fd == 0: # stdin
			do_stdin(stdin, irc)
		else: # irc fd
			do_irc(irc)