~azzar1/unity/add-show-desktop-key

# 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 md5

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 = md5.new(env['content'] + magic).digest().encode('hex')

            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 = md5.new(content + magic).digest().encode("hex")

    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