http_serve4.py

#!/usr/bin/env python

import socket 
import os

import httpdate

host = '' # listen on all connections (WiFi, etc) 
port = 50000 
backlog = 5 # how many connections can we stack up
size = 1024 # number of bytes to receive at once

print "point your browser to http://localhost:%i"%port

## create the socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 
# set an option to tell the OS to re-use the socket
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

# the bind makes it a server
s.bind( (host,port) ) 
s.listen(backlog) 

def OK_response(entity):
    """
    returns an HTTP response: header and entity in a string
    """
    resp = []
    resp.append('HTTP/1.1 200 OK')
    resp.append(httpdate.httpdate_now())
    resp.append( 'Content-Type: text/plain' )
    resp.append('Content-Length: %i'%len(entity))
    resp.append('')
    resp.append(entity)

    return "\r\n".join(resp)

def Error_response(URI):
    """
    returns an HTTP 404 Not Found Error response:
    
    URI is the name of the entity not found 
    """
    resp = []
    resp.append('HTTP/1.1 404 Not Found')
    resp.append(httpdate.httpdate_now())
    resp.append('Content-Type: text/plain')
    
    msg = "404 Error:\n %s \n not found"%( URI )    

    resp.append('Content-Length: %i'%( len(msg) ) )
    resp.append('')
    resp.append(msg)

    return "\r\n".join(resp)


def parse_request(request):
    """
    parse an HTTP request 
    
    returns the URI asked for
    
    note: minimal parsing -- only supprt GET
    
    example:
    GET / HTTP/1.1
    Host: localhost:50000
    User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:12.0) Gecko/20100101 Firefox/12.0
    Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
    Accept-Language: en-us,en;q=0.5
    Accept-Encoding: gzip, deflate
    Connection: keep-alive
    Cache-Control: max-age=0
    """
    # first line should be the method line:
    lines = request.split("\r\n")
    print lines
    
    method, URI, protocol = lines[0].split()
    print method
    print URI
    print protocol
    # a bit of checking:
    if method.strip() != "GET":
        raise ValueError("I can only process a GET request") 
    if protocol.split('/')[0] != "HTTP":
        raise ValueError("I can only process an HTTP request") 

    return URI

def format_dir_list(dir_list):
    msg = ["Directory Listing:"]
    for d in dir_list:
        msg.append(d)
    return "\n".join(msg)

def get_file(URI):
    root_dir = 'web' # must be run from code dir...
    URI = URI.lstrip('/') # os.path.join does not like a leading slash
    filename = os.path.join( root_dir, URI)
    print "path to file:", filename
    if os.path.isfile(filename):
        print "it's a file"
        raise NotImplementedError("I can't handle a file yet")
    elif os.path.isdir(filename):
        print "it's a dir"
        return format_dir_list(os.listdir(filename)), 'txt'
    else:
        raise ValueError("there is nothing by that name")    

while True: # keep looking for new connections forever
    client, address = s.accept() # look for a connection
    request = client.recv(size)
    if request: # if the connection was closed there would be no data
        print "received:", request
        URI = parse_request(request)
        print "URI requested is:", URI
        try:
            file_data, ext = get_file(URI)
            response = OK_response(file_data)
        except ValueError as err:
            print err
            response = Error_response(URI)
        print "sending:"
        print response[:200]
        client.send(response) 
        client.close()