Port Scanner com Tkinter

from tkinter import *
from socket import *

fonte = font=("Arial","11")
c = "gray15"
co = "green2"
scanner = Tk()

lb = Label(scanner, text="Port Scanner", font=("Gang of Three", "20"), bg=c, fg=co)
lb.place(x=1, y=1)

lb1 = Label(scanner, text="URL ou IP", font=fonte, bg=c, fg=co)
lb1.place(x=5, y=50)

inf = Entry(scanner, font=fonte, bg="gray10", fg="white")
inf.place(x=80, y=50)

ed12 = Text(scanner, font=("Arial","12", "bold"), bg="gray10", fg="white", width=43, height=18, selectbackground="green2", selectforeground="gray10")
ed12.place(x=5, y=140)

lb2 = Label(scanner, text="Início", font=fonte, bg=c, fg=co)
lb2.place(x=5, y=80)

ini = Entry(scanner, font=fonte, bg="gray10", fg="white")
ini.place(x=80, y=80)

lb3 = Label(scanner, text="Fim", font=fonte, bg=c, fg=co)
lb3.place(x=5, y=110)

fim = Entry(scanner, font=fonte, bg="gray10", fg="white")
fim.place(x=80, y=110)

def scan():
    ed12.delete(0.0)
    a = int(ini.get())
    b = int(fim.get())
    aa = a-1
    url = inf.get()
    lista = range(b, aa, -1)
    for i in lista:
        a = socket(AF_INET, SOCK_STREAM)
        a.settimeout(0.5)
        b = a.connect_ex((url, i))
        if b!= 0:
            ed12.insert(0.0, "A porta {} está fechada\n".format(i))
        else:
            ed12.insert(0.0, "A porta {} está aberta\n".format(i))
bt = Button(scanner, text="Iniciar", width=15, font=fonte, bg="gray10", fg=co, activebackground=c, activeforeground=co, command=scan)
bt.place(x=243, y=500)

scanner["bg"] = "gray15"
scanner.resizable(height=False, width=False)
scanner.title("Port Scanner")
scanner.geometry("400x540+450+20")
scanner.mainloop()