Tidied up version of @cymplecy's code

sw.py

#Original Code Martin Bateman 2013
#Modified by Simon Walters
#GPLv2 applies
#PC End
#V0.2 04Aug13

import sys 
import time
import socket 
import Tkinter as Tk

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.bind(('', 0)) 
s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
four_digits = "12aa"

if len(sys.argv) > 1:
    message = sys.argv[1]
else:
    message = "Start SID" + four_digits

def onOpen():
    message = "Start SID" + four_digits
    progress.set("New Text!")
    for i in range(0,10):
        s.sendto(message, ('<broadcast>', 50000))
        time.sleep(2)

def onExit():
    sys.exit()

root = Tk.Tk()
progress = Tk.StringVar(root)
root.title('Find a SID')
Tk.Label (text='enter the file name').pack(side=Tk.TOP,padx=10,pady=10)
Tk.Label (textvariable=progress).pack(side=Tk.TOP,padx=10,pady=10)
Tk.Entry(root, width=10).pack(side=Tk.TOP,padx=10,pady=10)
Tk.Button(root, text='open', command=onOpen).pack(side=Tk.LEFT)
#Button(root, text='exit').pack(side= RIGHT)
#Button(root, text='close').pack(side= RIGHT)
root.mainloop()