#!/usr/bin/env python3
'''
    tcp_demo.py
    Jeff Ondich, 14 September 2016

    A simple-minded example of how to open a TCP connection to a known
    web server and request a file there. Read the comments below to
    help you think about the many, many ways this program is not ready for
    production use.
'''
import socket

# Host and port to which we want to connect. Port 80 is
# the conventional (but not universal) port for web servers.
host = 'cs.carleton.edu'
port = 80

# The underlying socket system, written in C, requires the
# caller of sockte.rcv to specify both a buffer into which to read
# data and the length of that buffer so the data won't overflow
# the buffer. Even though Python reads the data using automatically
# resizing buffer objects (typically type str), the C interface
# bleeds into Python here, and requires that we specify a maximum
# size for each rcv operation.
block_size = 1000

# Pieces of the HTTP query
get_line = 'GET /faculty/jondich/index.html HTTP/1.1\r\n'
user_agent_line = 'User-Agent: Jeff\'s TCP Demo\r\n'
host_line = 'Host: ' + host + '\r\n'
http_query = get_line + user_agent_line + host_line + '\r\n'

# Make the TCP connection and, just for fun, print out the name
# of the server.
sock = socket.create_connection((host, port))
print('Peer name: ', sock.getpeername())
print()

# Make the HTTP query and print the retrieved data. Call rcv on the
# socket repeatedly until you get either an empty string or a None back.
#
# Note that in Python 3, the sendall method expects a parameter of type "bytes"
# (not a "str"), and rcv returns an object of type "bytes" as well. So in
# this example, where we know ahead of time that the data will be UTF8-encoded
# strings, we use encode and decode to move between bytes and str objects.
sock.sendall(http_query.encode('utf-8'))
data = sock.recv(block_size)
while data:
    print(data.decode('utf-8'))
    data = sock.recv(block_size)
sock.close()

# See any security errors here?
# Hint #1: what evil things could the server do?
# Hint #2: what assumptions are we making about the data we get back?