[Tutor] Help debuging a small program

[Kent Johnson]

Mark Kels wrote:
> Hi list !
> Here is a small port scanner I made to practice sockets and GUI
> programming ( WARNING: the program crash when scan button is clicked):

How far does it get? How do you know?

I would put some debug print statements in. Also you should call sk.close() in the else clause of 
scan(). Finally, I don't think you will see any output in the result window until get_info() 
returns; you have to give some time to mainloop() for it to be able to trigger the updates.

> 
> #----------Imports----------
> from Tkinter import * 
> import socket
> #----------The result GUI window function---------
> def result():
>     global result_t #I made result_t global so I will be able to
> insert data into it from the scan function
>     r_root=Toplevel(root)
>     result_t=Text(r_root)
>     result_t.pack()
>     
> #----------Command Functions----------
> # + ---Function to get the info from the gui and start the scan---
> def get_info():
>     result()
>     host=host_e.get()
>     start_port=int(start_port_e.get())
>     end_port=int(end_port_e.get())
>     scan(host,start_port,end_port)
> 
> # + ---The Scan---
> def scan(host,start_port,end_port):
>     sk=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
>     while start_port<=end_port:
>         try:
>             sk.connect((host,start_port))
>         except:
>             result_t.insert(END,"Port",start_port,"is CLOSED on",host,"\n")
>         else:
>             result_t.insert(END,"Port",start_port,"is OPENED on",host,"\n")
>         start_port=start_port+1
>         
> #----------The main GUI window----------        
> root=Tk()
> Label(root,text="Host: ").grid(row=1,column=1)
> host_e=Entry(root)
> host_e.grid(row=1,column=2)
> Label(root,text="Start port: ").grid(row=2,column=1)
> start_port_e=Entry(root)
> start_port_e.grid(row=2,column=2)
> Label(root,text="End port: ").grid(row=3,column=1)
> end_port_e=Entry(root)
> end_port_e.grid(row=3,column=2)
> Button(root,text="Scan",command=get_info).grid(row=5,column=1)
> 
> root.mainloop()
> 
> Why does the program crash (without any errors :-/ ) when I click the
> Scan button ??
>