server.py

####################################################################################
# variables   b1,b2
# threads     main,thread_to_read_bot1_move_from_file,thread_to_read_bot2_move_from_file
# locks       bot1move_lock,bot2_move_lock
##################################################################################


#!/usr/bin/python

import threading
import time
import sys
b1='U' #bot1s current move
b2='R' #bot2s current move

bot1_move_lock=threading.Lock() #lock to provide synchronisation to b1
bot2_move_lock=threading.Lock() #lock ot provide syncrhonisation to b2


exitFlag = 0


class thread_to_read_bot1_move_from_file (threading.Thread):

    def __init__(self, threadID,filename):
        self.threadID = threadID
        threading.Thread.__init__(self)

    def run(self):
        global b1
        print "Starting " + str(self.threadID)
        bot1_move_lock.acquire()
        print "Before" +  b1
        b1='L'
        print "After" +  b1
        bot1_move_lock.release()
        print "Exiting " + str(self.threadID)

class thread_to_read_bot2_move_from_file (threading.Thread):

    def __init__(self, threadID,filename):
        self.threadID = threadID
        threading.Thread.__init__(self)

    def run(self):
        global b1
        print "Starting " + str(self.threadID)
        bot2_move_lock.acquire()
        print "Before" +  b1
        b2='L'
        print "After" +  b1
        bot2_move_lock.release()
        print "Exiting " + str(self.threadID)

#start threads
bot1_move_file=open("files/bot1_move","r")
bot2_move_file=open("files/bot2_move","r")
thread1 = thread_to_read_bot1_move_from_file(1,bot1_move_file)
thread2 = thread_to_read_bot2_move_from_file(1,bot2_move_file)
thread1.start()
thread2.start()




#    the rest of the engine code which will constantly read the variables b1 and b2
#    and update the map. The variables b1 and b2 will have to be locked before reading 
#    (or may b not)
#    This is jus test code. b1 initaised as above . The threads individually write to
#    it by reading from the respective files. This main thread will read b1 and b2 and
#    move the bot accordingly.
while(True):
    if ( thread1.isAlive() or thread2.isAlive()):
        continue
    if( bot1_move_lock.acquire(False) && bot2_move_lock_acquire(False)):

        print b1,b2
        break
    else:
        pass
                

print "Exiting main thread"