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# IVLE - Informatics Virtual Learning Environment
# Copyright (C) 2007-2008 The University of Melbourne
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
# Module: Chat
# Author: Thomas Conway
# Date: 5/2/2008
import cjson
import cStringIO
import hashlib
import sys
import os
import socket
import traceback
class Terminate(Exception):
"""Exception thrown when server is to be shut down. It will attempt to sned
the final_response to the client and then exits"""
def __init__(self, final_response=None):
self.final_response = final_response
def __str__(self):
return repr(self.final_response)
def start_server(port, magic, daemon_mode, handler, initializer = None):
# Attempt to open the socket.
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(('', port))
s.listen(1)
# Excellent! It worked. Let's turn ourself into a daemon,
# then get on with the job of being a python interpreter.
if daemon_mode:
if os.fork(): # launch child and...
os._exit(0) # kill off parent
os.setsid()
if os.fork(): # launch child and...
os._exit(0) # kill off parent again.
os.umask(077)
try:
MAXFD = os.sysconf("SC_OPEN_MAX")
except:
MAXFD = 256
# Close all file descriptors, except the socket.
for i in xrange(MAXFD):
if i == s.fileno():
continue
try:
os.close(i)
except OSError:
pass
si = os.open(os.devnull, os.O_RDONLY)
os.dup2(si, sys.stdin.fileno())
so = os.open(os.devnull, os.O_WRONLY)
os.dup2(so, sys.stdout.fileno())
se = os.open(os.devnull, os.O_WRONLY)
os.dup2(se, sys.stderr.fileno())
if initializer:
initializer()
while True:
(conn, addr) = s.accept()
try:
# Grab the input
buf = cStringIO.StringIO()
blk = conn.recv(1024)
while blk:
buf.write(blk)
try:
blk = conn.recv(1024, socket.MSG_DONTWAIT)
except:
# Exception thrown if it WOULD block (but we
# told it not to wait) - ie. we are done
blk = None
inp = buf.getvalue()
env = cjson.decode(inp)
# Check that the message is
digest = hashlib.md5(env['content'] + magic).hexdigest()
if env['digest'] != digest:
conn.close()
continue
content = cjson.decode(env['content'])
response = handler(content)
conn.sendall(cjson.encode(response))
conn.close()
except Terminate, t:
# Try and send final response and then terminate
if t.final_response:
conn.sendall(cjson.encode(t.final_response))
conn.close()
sys.exit(0)
except Exception:
# Make a JSON object full of exceptional goodness
tb_dump = cStringIO.StringIO()
e_type, e_val, e_tb = sys.exc_info()
traceback.print_tb(e_tb, file=tb_dump)
json_exc = {
"type": e_type.__name__,
"value": str(e_val),
"traceback": tb_dump.getvalue()
}
conn.sendall(cjson.encode(json_exc))
conn.close()
def chat(host, port, msg, magic, decode = True):
sok = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sok.connect((host, port))
content = cjson.encode(msg)
digest = hashlib.md5(content + magic).hexdigest()
env = {'digest':digest,'content':content}
sok.send(cjson.encode(env))
buf = cStringIO.StringIO()
blk = sok.recv(1024)
while blk:
buf.write(blk)
try:
blk = sok.recv(1024, socket.MSG_DONTWAIT)
except socket.error, e:
if e[0] != 11:
raise
# Exception thrown if it WOULD block (but we
# told it not to wait) - ie. we are done
blk = None
inp = buf.getvalue()
sok.close()
if decode:
return cjson.decode(inp)
else:
return inp
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