import socket
import sys
from urllib.parse import urlparse
import select
s = socket.socket(type=socket.SOCK_DGRAM)
url = urlparse(sys.argv[1])
s.connect((url.hostname, 6775))
request = (sys.argv[1] + "\r\n").encode('utf-8')
sys.stderr.write(f"Sending request for {sys.argv[1]}\n")
s.send(request)
buffered = b''
mime_type = None
tries = 0
last_buffered = 0
chunks = {}
while True:
ready, _, _ = select.select([s.fileno()], [], [], 2)
# if we still haven't received anything from the server, retry the request
if len(chunks) == 0 and not ready:
if tries > 5:
raise Exception("All 5 tries have failed")
sys.stderr.write(f"Retrying request for {sys.argv[1]}\n")
s.send(request)
tries += 1
continue
# if we're waiting for packet n+1, retry ack packet n
if not ready and last_buffered > 0:
sys.stderr.write(f"Retrying ack for packet {last_buffered}\n")
s.send(f"{last_buffered}\r\n".encode('utf-8'))
continue
# receive and parse the next packet
pkt = s.recv(4096)
crlf = pkt.index(b'\r\n')
header = pkt[:crlf]
try:
# parse the success packet header
space = header.index(b' ')
seq = int(header[:space])
mime_type = header[space + 1:]
if seq == 4:
raise Exception(f"Error: {mime_type.decode('utf-8')}")
if seq == 3:
raise Exception(f"Redirected to {mime_type.decode('utf-8')}")
if seq == 1:
raise Exception(f"Input required: {mime_type.decode('utf-8')}")
if seq < 6:
raise Exception(f"Invalid status code: {seq}")
except ValueError as e:
# parse the continuation or EOF packet header
seq = int(header)
if seq in chunks:
sys.stderr.write(f"Ignoring duplicate packet {seq} and resending ack\n")
s.send(f"{seq}\r\n".encode('utf-8'))
continue
if last_buffered == 0 and mime_type is not None:
sys.stderr.write(f"Response is of type {mime_type.decode('utf-8')}\n")
sys.stderr.write(f"Sending ack for packet {seq}\n")
s.send(f"{seq}\r\n".encode('utf-8'))
data = pkt[crlf + 2:]
if last_buffered == 0 or seq == last_buffered + 1:
sys.stderr.write(f"Received packet {seq} with {len(data)} bytes of data\n")
else:
sys.stderr.write(f"Received out-of-order packet {seq} with {len(data)} bytes of data\n")
chunks[seq] = data
# concatenate the consequentive response chunks we have
while (last_buffered == 0 and mime_type is not None) or seq == last_buffered + 1:
data = chunks[seq]
sys.stderr.write(f"Queueing packet {seq} for display\n")
buffered += data
last_buffered = seq
# print the buffered text if we can
try:
print(buffered.decode('utf-8'))
last_buffered = seq
sys.stderr.write("Flushed the buffer to screen\n")
buffered = b''
except UnicodeDecodeError:
sys.stderr.write("Cannot print buffered text until valid UTF-8\n")
continue
# stop once we printed everything until the end-of-file packet
if not chunks[last_buffered]:
sys.stderr.write("Reached end of document\n")
break