Projects/Netlight

Project Netlight
Name	Netlight
Start	2012-07-27
End	2012-07-29
Contact	User:Pietdv
Website
Information	The network traffic light at haxogreen
Status	Production

Because of a faulty switch the network at haxogreen 2012 was quite buggy for a while. After a couple of hours we were sick of opening up a terminal and starting a ping to check if the internet was up. We had a raspi and a traffic light available, so we started hacking. We made a little relay board to let the raspi control the traffic light, and wrote a shell script to check if there was an internet connection and set the traffic light to green if there was, to red if there wasn't.

http://www.youtube.com/watch?v=uxdJv-h0Fks

Update 28/07/12

We made a new relay board so we can control the two light independently, When the raspi is booting both lights are now off.

Update 28/07/12 nr2

We ported the code to Python. When there is only a limited amount of package loss, the lights now blinks.

People who helped

• Pietdv
• gmc
• Zarya

Gallery

• 
• 

  Raspberry PI with a relay board connected to it

• 

  The schematic of the relay board

Script

1. !/usr/bin/env python

"""

   A pure python ping implementation using raw socket.


   Note that ICMP messages can only be sent from processes running as root.


   Derived from ping.c distributed in Linux's netkit. That code is
   copyright (c) 1989 by The Regents of the University of California.
   That code is in turn derived from code written by Mike Muuss of the
   US Army Ballistic Research Laboratory in December, 1983 and
   placed in the public domain. They have my thanks.

   Bugs are naturally mine. I'd be glad to hear about them. There are
   certainly word - size dependenceies here.

   Copyright (c) Matthew Dixon Cowles, <http://www.visi.com/~mdc/>.
   Distributable under the terms of the GNU General Public License
   version 2. Provided with no warranties of any sort.

   Original Version from Matthew Dixon Cowles:
     -> ftp://ftp.visi.com/users/mdc/ping.py

   Rewrite by Jens Diemer:
     -> http://www.python-forum.de/post-69122.html#69122

   Rewrite by George Notaras:
     -> http://www.g-loaded.eu/2009/10/30/python-ping/

   Revision history
   22:12, 28 July 2012 (CEST)22:12, 28 July 2012 (CEST)22:12, 28 July 2012 (CEST)~

   November 8, 2009
   ----------------
   Improved compatibility with GNU/Linux systems.

   Fixes by:
    * George Notaras -- http://www.g-loaded.eu
   Reported by:
    * Chris Hallman -- http://cdhallman.blogspot.com

   Changes in this release:
    - Re-use time.time() instead of time.clock(). The 2007 implementation
      worked only under Microsoft Windows. Failed on GNU/Linux.
      time.clock() behaves differently under the two OSes[1].

   [1] http://docs.python.org/library/time.html#time.clock

   May 30, 2007
   ------------
   little rewrite by Jens Diemer:
    -  change socket asterisk import to a normal import
    -  replace time.time() with time.clock()
    -  delete "return None" (or change to "return" only)
    -  in checksum() rename "str" to "source_string"

   November 22, 1997
   -----------------
   Initial hack. Doesn't do much, but rather than try to guess
   what features I (or others) will want in the future, I've only
   put in what I need now.

   December 16, 1997
   -----------------
   For some reason, the checksum bytes are in the wrong order when
   this is run under Solaris 2.X for SPARC but it works right under
   Linux x86. Since I don't know just what's wrong, I'll swap the
   bytes always and then do an htons().

   December 4, 2000
   ----------------
   Changed the struct.pack() calls to pack the checksum and ID as
   unsigned. My thanks to Jerome Poincheval for the fix.


   Last commit info:
   22:12, 28 July 2012 (CEST)22:12, 28 July 2012 (CEST)22:12, 28 July 2012 (CEST)~~
   $LastChangedDate: $
   $Rev: $
   $Author: $

"""

import os, sys, socket, struct, select, time

1. From /usr/include/linux/icmp.h; your milage may vary.

ICMP_ECHO_REQUEST = 8 # Seems to be the same on Solaris.

IP="8.8.8.8" TIMEOUT=0.4 GREENPIN=24 REDPIN=23 HISTORY=10

def checksum(source_string):

   """
   I'm not too confident that this is right but testing seems
   to suggest that it gives the same answers as in_cksum in ping.c
   """
   sum = 0
   countTo = (len(source_string)/2)*2
   count = 0
   while count<countTo:
       thisVal = ord(source_string[count + 1])*256 + ord(source_string[count])
       sum = sum + thisVal
       sum = sum & 0xffffffff # Necessary?
       count = count + 2

   if countTo<len(source_string):
       sum = sum + ord(source_string[len(source_string) - 1])
       sum = sum & 0xffffffff # Necessary?

   sum = (sum >> 16)  +  (sum & 0xffff)
   sum = sum + (sum >> 16)
   answer = ~sum
   answer = answer & 0xffff

   # Swap bytes. Bugger me if I know why.
   answer = answer >> 8 | (answer << 8 & 0xff00)

   return answer

def receive_one_ping(my_socket, ID, timeout):

   """
   receive the ping from the socket.
   """
   timeLeft = timeout
   while True:
       startedSelect = time.time()
       whatReady = select.select([my_socket], [], [], timeLeft)
       howLongInSelect = (time.time() - startedSelect)
       if whatReady[0] == []: # Timeout
           return

       timeReceived = time.time()
       recPacket, addr = my_socket.recvfrom(1024)
       icmpHeader = recPacket[20:28]
       type, code, checksum, packetID, sequence = struct.unpack(
           "bbHHh", icmpHeader
       )
       if packetID == ID:
           bytesInDouble = struct.calcsize("d")
           timeSent = struct.unpack("d", recPacket[28:28 + bytesInDouble])[0]
           return timeReceived - timeSent

       timeLeft = timeLeft - howLongInSelect
       if timeLeft <= 0:
           return

def send_one_ping(my_socket, dest_addr, ID):

   """
   Send one ping to the given >dest_addr<.
   """
   dest_addr  =  socket.gethostbyname(dest_addr)

   # Header is type (8), code (8), checksum (16), id (16), sequence (16)
   my_checksum = 0

   # Make a dummy heder with a 0 checksum.
   header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, my_checksum, ID, 1)
   bytesInDouble = struct.calcsize("d")
   data = (192 - bytesInDouble) * "Q"
   data = struct.pack("d", time.time()) + data

   # Calculate the checksum on the data and the dummy header.
   my_checksum = checksum(header + data)

   # Now that we have the right checksum, we put that in. It's just easier
   # to make up a new header than to stuff it into the dummy.
   header = struct.pack(
       "bbHHh", ICMP_ECHO_REQUEST, 0, socket.htons(my_checksum), ID, 1
   )
   packet = header + data
   my_socket.sendto(packet, (dest_addr, 1)) # Don't know about the 1

def do_one(dest_addr, timeout):

   """
   Returns either the delay (in seconds) or none on timeout.
   """
   icmp = socket.getprotobyname("icmp")
   try:
       my_socket = socket.socket(socket.AF_INET, socket.SOCK_RAW, icmp)
   except socket.error, (errno, msg):
       if errno == 1:
           # Operation not permitted
           msg = msg + (
               " - Note that ICMP messages can only be sent from processes"
               " running as root."
           )
           raise socket.error(msg)
       raise # raise the original error

   my_ID = os.getpid() & 0xFFFF

   send_one_ping(my_socket, dest_addr, my_ID)
   delay = receive_one_ping(my_socket, my_ID, timeout)

   my_socket.close()
   return delay

def verbose_ping(dest_addr, timeout = 2, count = 4):

   """
   Send >count< ping to >dest_addr< with the given >timeout< and display
   the result.
   """
   for i in xrange(count):
       print "ping %s..." % dest_addr,
       try:
           delay  =  do_one(dest_addr, timeout)
       except socket.gaierror, e:
           print "failed. (socket error: '%s')" % e[1]
           break

       if delay  ==  None:
           print "failed. (timeout within %ssec.)" % timeout
       else:
           delay  =  delay * 1000
           print "get ping in %0.4fms" % delay
   print

def set_pin(pin,value):

   file('/sys/class/gpio/gpio'+str(pin)+'/value','w').write(str(value))

def blink_pin(pin,f):

   t=time.time()
   t=t-int(t)
   if t < 0.5:
     set_pin(pin,1)
   else:
     set_pin(pin,0)

def init_pin(pin):

 file('/sys/class/gpio/export','w').write(str(pin))
 file('/sys/class/gpio/gpio'+str(pin)+'/direction','w').write('out')

if __name__ == '__main__':

   count=0
   loss=0

   init_pin(REDPIN);
   init_pin(GREENPIN);
 
   while 1 == 1:
       lasttime=time.time() 
       print time.time()
       if count>(HISTORY-1):
           count=count-1
           if loss>(HISTORY-1):
             loss=loss-1
       ping = None
       try:
         ping = do_one(IP,TIMEOUT)
       except:
         pass
       count=count+1
       if ping == None:
           loss=loss+1
       elif loss>0:
           loss=loss-1
       
       print "ping "+str(count)+", loss "+str(loss)
       if loss==0:
           set_pin(REDPIN,0)
           set_pin(GREENPIN,1)
       elif loss==count:
           set_pin(GREENPIN,0)
           set_pin(REDPIN,1)
       else:
           set_pin(GREENPIN,1)
           blink_pin(REDPIN,0.2+((1.0-(float(loss)/float(count)))/2.0))
       wait = lasttime+1 - time.time()
       print wait
       if loss==0 and wait:
          time.sleep(wait)