Python Webserver not working

Question

I am building a basic python web server, but I keep having a problem where it is not sending any data (by the way I am accessing the website on the same computer as it is running on and I have the file which the server is trying to access) here is my code:

import socket

HOST, PORT = '', 80

def between(left,right,s):
    before,_,a = s.partition(left)
    a,_,after = a.partition(right)
    return a

filereq = ""
listen_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
listen_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
listen_socket.bind((HOST, PORT))
lines = []
print("Started!")
listen_socket.listen(1)
print("Listening")
while True:
        try:
                lines = []
                client_connection, client_address = listen_socket.accept()
                print("Connected")
                request = client_connection.recv(1024)
                print("Received Data!")
                filereq = between("GET /", " HT", request)
                print(filereq)
                filereq = open(filereq)
                for line in filereq:
                        lines.append(line)
                print(lines)
                sendata = ''.join(lines)
                print(sendata)
                http_response = """\
                HTTP/1.1 200 OK 

                {}
                """.format(sendata)
                print(http_response)
                client_connection.sendall(http_response)
                print("Sent the Data!")
                client_connection.close()
                print("Connection Closed!")
        except:
                5+5

Answer 1

The problem is that the server is implemented in Python3 but the code mixes bytes and strings, which works in Python2 but not Python3.

This causes an error in the between function, because partition is being called on a bytes object but is being provided with str separator values.

>>> data = b'abc'
>>> data.partition('b')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: a bytes-like object is required, not 'str'

To fix this, decode the data from bytes to str when read from the socket, then encode back to bytes before sending the response (socket.sendall expects bytes as an argument).

Also, print out any exceptions that occur so that you can debug them.

import socket
import sys
import traceback

HOST, PORT = '', 80

def between(left,right,s):
    before,_,a = s.partition(left)
    a,_,after = a.partition(right)
    return a

filereq = ""
listen_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
listen_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
listen_socket.bind((HOST, PORT))
lines = []
print("Started!")
listen_socket.listen(1)
print("Listening")
while True:
        try:
                lines = []
                client_connection, client_address = listen_socket.accept()
                print("Connected")
                request = client_connection.recv(1024)
                print("Received Data!")

                # Decode the data before processing.
                decoded = request.decode('utf-8')
                filereq = between("GET /", " HT", decoded)
                print(filereq)
                filereq = open(filereq)
                for line in filereq:
                        lines.append(line)
                print(lines)
                sendata = ''.join(lines)
                print(sendata)
                http_response = """\
                HTTP/1.1 200 OK 

                {}
                """.format(sendata)
                print(http_response)

                # Encode the response before sending.
                encoded = http_response.encode('utf-8')
                client_connection.sendall(encoded)
                print("Sent the Data!")
                client_connection.close()
                print("Connection Closed!")
        except Exception:
                # Print the traceback if there's an error.
                traceback.print_exc(file=sys.stderr)