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Problems with sockets and threads

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  Problems with sockets and threads Dexter Deejay <djdexter1389@gmail.com> - 2013-04-11 05:14 -0700
    Re: Problems with sockets and threads Wayne Werner <wayne@waynewerner.com> - 2013-04-11 07:27 -0500
    Re: Problems with sockets and threads Dexter Deejay <djdexter1389@gmail.com> - 2013-04-11 05:34 -0700
      Re: Problems with sockets and threads Wayne Werner <wayne@waynewerner.com> - 2013-04-11 08:03 -0500
    Re: Problems with sockets and threads Dexter Deejay <djdexter1389@gmail.com> - 2013-04-11 06:10 -0700
    Re: Problems with sockets and threads Dexter Deejay <djdexter1389@gmail.com> - 2013-04-11 06:11 -0700
      Re: Problems with sockets and threads Dexter Deejay <djdexter1389@gmail.com> - 2013-04-11 07:21 -0700
    Re: Problems with sockets and threads Peter Otten <__peter__@web.de> - 2013-04-11 16:41 +0200
      Re: Problems with sockets and threads Dexter Deejay <djdexter1389@gmail.com> - 2013-04-11 08:39 -0700
      Re: Problems with sockets and threads Dexter Deejay <djdexter1389@gmail.com> - 2013-04-11 08:39 -0700

#43357 — Problems with sockets and threads

When i try to run this code and to connect to server (server is written in java that part of code is ok) everything stalls. Thread that i created here occupies processor all the time and GUI freezes. It's supposed to be waiting for message from server. (asynchronous one) Is there something that i did wrong here, or is there better way to do this?


from tkinter import *
from threading import *
import time
import socket
import sys

comPort=0
msg=""
name=socket.gethostbyname(socket.gethostname())
sock=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
testArea=0
thread=0

def threadFunc():
    global sock
    global textArea
    data=""
    while(data==""):
        try:
            data=str((sock.recvfrom(256)),"UTF-8")
        except BlockingIOError:
            print("failed")
            time.sleep(1)
            data=""
    textArea.add((data+"\n"))

def sendMsg():
    global sock
    message=name+": "+msg.get()+"\n"
    sock.send(bytes(message,"UTF-8"))

def aboutCommand():
    messagebox.showinfo(title="About",message="This is first (serious) aplication in python.")

def helpCommand():
    messagebox.showinfo(title="Help",message="BAZINGA!")

def Connect():
    global sock
    global thread
    sock.connect((serverIPString.get(), 16000))
    sock.send(bytes("#connect request#\n",'UTF-8'))
    data=sock.recvfrom(256)
    reply=str(data[0],"UTF-8")
    answer=(reply.split("#",3))
    if(answer[1]!="connected"):
        messagebox.showinfo(title="Error",message="Connection failed!")
        return
    sock.close();
    sock=None
    comPort=int(answer[2])       #for new connection
    sock=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((serverIPString.get(), comPort))
    sock.setblocking(0)
    thread=Thread(target=threadFunc())
    thread.start()

def Disconnect():
    global sock
    sock.send(bytes("#END#\n","UTF-8"))
    sock.close()

def ExitApplication():
    Disconnect()
    mGui.destroy()
    return

mGui=Tk()
msg=StringVar()
serverIPString=StringVar()
mGui.geometry("400x600+200+20")
mGui.title("Chat client v1.0")

labServer=Label(mGui,text="Server IP adress: ").pack()
entServer=Entry(mGui,textvariable=serverIPString).pack()
btnConnect=Button(mGui,text="Connect",fg="red",bg="blue",command=Connect).pack()
btnDisconnect=Button(mGui,text="Disconnect",fg="red",bg="blue",command=Disconnect).pack()
textArea=Text(mGui,bg="yellow").pack()
entMessage=Entry(mGui,textvariable=msg).pack()
btnSendMsg=Button(mGui,text="Send message",fg="white",bg="black",command=sendMsg).pack()

menuBar=Menu(mGui)

fileMenu=Menu(menuBar,tearoff=0)
fileMenu.add_command(label="Exit",command=ExitApplication)
menuBar.add_cascade(label="File",menu=fileMenu)

optionsMenu=Menu(menuBar,tearoff=0)
optionsMenu.add_command(label="Change chat name")
optionsMenu.add_command(label="Connect",command=Connect)
optionsMenu.add_command(label="Disconnect",command=Disconnect)
menuBar.add_cascade(label="Options",menu=optionsMenu)

helpMenu=Menu(menuBar,tearoff=0)
helpMenu.add_command(label="Help",command=helpCommand)
helpMenu.add_command(label="About",command=aboutCommand)
menuBar.add_cascade(label="Info",menu=helpMenu)
mGui.config(menu=menuBar)
mGui.mainloop()

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#43359

On Thu, 11 Apr 2013, Dexter Deejay wrote:

> When i try to run this code and to connect to server (server is written in java that part of code is ok) everything stalls. Thread that i created here occupies processor all the time and GUI freezes. It's supposed to be waiting for message from server. (asynchronous one) Is there something that i did wrong here, or is there better way to do this?
>
>
> from tkinter import *
> from threading import *

Everything I've read or used suggests to me that threading+tkinter is a 
dangerous combination.

Mainly because tkinter already has an event loop, so when you start mixing 
threads things tend to go sideways.

Instead what you'll want to do is put processing in the .after or 
.after_idle callbacks - just make sure that whatever is doing is quick (or 
can do a portion of the activity quickly).

HTH,
-W

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#43361

Yeah, that seems to be problem. Waiting for message is in theory infinite. But why doesn't this separate thread leave processor while it is sleeping?

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#43363

On Thu, 11 Apr 2013, Dexter Deejay wrote:

> Yeah, that seems to be problem. Waiting for message is in theory infinite. But why doesn't this separate thread leave processor while it is sleeping?

As far as I've been able to tell? Magic ;)

But I haven't really dug into it. If you're really doing some waiting 
stuff you might want to look into some other type of message passing 
mechanism, e.g. launch a subprocess to do ths listening and then writing 
to a file and checking that from within Tkinter. I expect there are other 
possibilities that more advanced people may be able to recommend and are 
probably better. But that seems like it would work.

HTH,
-W

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#43364

Thanks for help. Do you have any reference to pint me out for that subprocess creation?

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#43365

Thanks for help. Do you have any reference to direct me for that subprocess creation? 

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#43373

FOUND ERROR! :D In creatin method of thread i wrote treadFunc() and should have said threadFunc (as pointer). Now i have problem with Text component. How to append string at end of it?

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#43376

Dexter Deejay wrote:

> When i try to run this code and to connect to server (server is written in
> java that part of code is ok) everything stalls. Thread that i created
> here occupies processor all the time and GUI freezes. It's supposed to be
> waiting for message from server. (asynchronous one) Is there something
> that i did wrong here, or is there better way to do this?

Fredrik Lundh has an example that shows how to update a Text widget from 
another thread:

http://effbot.org/zone/tkinter-threads.htm

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#43382

Thanks! :D

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#43383

Thanks! :D

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