Re: link indirection

Daniel W. Connolly (connolly@hal.com)
Wed, 04 May 1994 10:40:05 -0500


In message <199405041523.AA03204@RA.DEPT.CS.YALE.EDU>, Stan Letovsky writes:
>into my code. I looked at Mosaic-2.4, and libwww2/HTTP.c seems to be
>the relevant piece, but it depends on a lot of other code in this
>module, and I would rather not have to include all of it if I
>don't have to.

You noticed this too, huh...

> Is there a bare-bones description of the client-side
>of the httpd protocol anywhere?

Lately, python is my favorite quick-and-dirty, but
precise programming language.

The cool think about python is that it's pretty easy
to grok, right out of the box. See for yourself:

(I didn't write this...guido did)

>From http://www.cwi.nl/~guido/python-src/Lib/httplib.py

# HTTP client class
#
# See the following document for a tentative protocol description:
# Hypertext Transfer Protocol (HTTP) Tim Berners-Lee, CERN
# Internet Draft 5 Nov 1993
# draft-ietf-iiir-http-00.txt Expires 5 May 1994
#
# Example:
#
# >>> from httplib import HTTP
# >>> h = HTTP('www.cwi.nl')
# >>> h.putreqest('GET', '/index.html')
# >>> h.putheader('Accept', 'text/html')
# >>> h.putheader('Accept', 'text/plain')
# >>> errcode, errmsg, headers = h.getreply()
# >>> if errcode == 200:
# ... f = h.getfile()
# ... print f.read() ## Print the raw HTML
# ...
# <TITLE>Home Page of CWI, Amsterdam</TITLE>
# [...many more lines...]
# >>>
#
# Note that an HTTP object is used for a single request -- to issue a
# second request to the same server, you create a new HTTP object.
# (This is in accordance with the protocol, which uses a new TCP
# connection for each request.)

import os
import socket
import string
import regex
import regsub
import rfc822

HTTP_VERSION = 'HTTP/1.0'
HTTP_PORT = 80

replypat = regsub.gsub('\\.', '\\\\.', HTTP_VERSION) + \
'[ \t]+\([0-9][0-9][0-9]\)\(.*\)'
replyprog = regex.compile(replypat)

class HTTP:

def __init__(self, *args):
self.debuglevel = 0
if args: apply(self.connect, args)

def set_debuglevel(self, debuglevel):
self.debuglevel = debuglevel

def connect(self, host, *args):
if args:
if args[1:]: raise TypeError, 'too many args'
port = args[0]
else:
i = string.find(host, ':')
port = None
if i >= 0:
host, port = host[:i], host[i+1:]
try: port = string.atoi(port)
except string.atoi_error: pass
if not port: port = HTTP_PORT
self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
if self.debuglevel > 0: print 'connect:', (host, port)
self.sock.connect(host, port)

def send(self, str):
if self.debuglevel > 0: print 'send:', `str`
self.sock.send(str)

def putrequest(self, request, selector):
str = '%s %s %s\r\n' % (request, selector, HTTP_VERSION)
self.send(str)

def putheader(self, header, *args):
str = '%s: %s\r\n' % (header, string.joinfields(args,'\r\n\t'))
self.send(str)

def endheaders(self):
self.send('\r\n')

def endrequest(self):
if self.debuglevel > 0: print 'shutdown: 1'
self.sock.shutdown(1)

def getreply(self):
self.endrequest()
self.file = self.sock.makefile('r')
line = self.file.readline()
if self.debuglevel > 0: print 'reply:', `line`
if replyprog.match(line) < 0:
self.headers = None
return -1, line, self.headers
errcode, errmsg = replyprog.group(1, 2)
errcode = string.atoi(errcode)
errmsg = string.strip(errmsg)
self.headers = rfc822.Message(self.file)
return errcode, errmsg, self.headers

def getfile(self):
return self.file

def test():
import sys
import getopt
opts, args = getopt.getopt(sys.argv[1:], 'd')
dl = 0
for o, a in opts:
if o == '-d': dl = dl + 1
host = 'www.cwi.nl:80'
selector = '/index.html'
if args[0:]: host = args[0]
if args[1:]: selector = args[1]
h = HTTP()
h.set_debuglevel(dl)
h.connect(host)
h.putrequest('GET', selector)
errcode, errmsg, headers = h.getreply()
print 'errcode =', errcode
print 'headers =', headers
print 'errmsg =', errmsg
if headers:
for header in headers.headers: print string.strip(header)
print h.getfile().read()

if __name__ == '__main__':
test()