Socket module causing BGE to freeze

Game Engine Game Engine Support and Discussion
1

hi, long story, but i am trying to use one computer to control another in BGE

basic idea is that i want to have someone hit the spacebar on computer 1 and it starts a top spinning on computer 2, and then makes it spin faster and faster with every press of the spacebar

problem is that the code on computer 2 (the top) causes it to freeze every time i hit ‘p’ to start BGE

it freezes both on windows and mac os x, so i’m pretty sure i’m doing something that python doesn’t like
(this is a real freeze - it’s not like waiting for something to happen and nothing’s happening - on mac, i quickly get the spinning pinwheel of death - on windows, i immediately get the grayed-out screen with ‘not responding’)

so, here’s the code on computer 2 (the top):

import bge
import socket

cont = bge.logic.getCurrentController()
own = cont.owner
spin = cont.actuators[“spin”]
spin.useLocalAngV = True

host = ‘’ # that is two single quotes, by the way, not one double quote
port = 50001
size = 1024
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((host,port))
s.listen(1)
spinSpeed = 0

while 1:
client, address = s.accept()
data = client.recv(size)
if data == “spaceBar”:
spinSpeed = spinSpeed + 1
spin.angV = [0, 0, spinSpeed]
cont.activate(spin)

although i don’t think it matters, just in case, here is the code on computer 1 (the computer where you press the spacebar):

import bge
import socket

cont = bge.logic.getCurrentController()
own = cont.owner
hitSpacebar = cont.sensors[“spaceBar”] # this is a spacebar-triggered sensor brick attached to the python controller

host = ‘localHost’
port = 50001
size = 1024
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((host,port))

if hitSpacebar.positive:
s.send(“spaceBar”)

any thoughts why computer 2 is always freezing when i hit ‘p’?

if it helps, i have found that it does not freeze when i delete the s.listen(1) line, but it doesn’t work either, i just get this error:

Python script error - object ‘Top’, controller ‘Python’:
Traceback (most recent call last):
File “spin.py”, line 73, in <module>
File “/Applications/Blender/blender.app/Contents/MacOS/2.70/python/lib/python3.3/socket.py”, line 135, in accept
fd, addr = self._accept()
OSError: [Errno 22] Invalid argument

2

Please use [noparse]

[/noparse] tags.

To help you on your problem: read your code again. Then read it sgain and read it … Again … until 1 is not 1 anymore.

3

You need a timeout. If I remember correctly, it gets locked in a while loop somewhere in the socket library. And so without a timeout it will “lock up” blender. I think the function that you need is something along the lines of socket.timout() or socket.setTimeout()

4 

while 1: 
   client, address = s.accept() 
   data = client.recv(size) 
   if data == "spaceBar":
     spinSpeed = spinSpeed + 1
    spin.angV = [0, 0, spinSpeed]
    cont.activate(spin)

How do you escape the while loop?
The game waits for you to exit the script.

5

Scripts run inside a single frame, so ports need to be non-blocking and infinote loops aren’t what you want.

6

Use asyncio


help(__import__("asyncio"))
7

thanks. i haven’t tried asyncio yet, but i have modified the code as follows to get rid of the ‘while 1’ loop and to use non-blocking —


import bge
import socket
cont = bge.logic.getCurrentController()
own = cont.owner
spin = cont.actuators["spin"] 
spin.useLocalAngV = True

host = '' # that is two single quotes, by the way, not one double quote
port = 50001  
size = 1024 
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 
s.bind((host,port)) 
s.listen(1)
s.settimeout(0) # this ensures non-blocking

spinSpeed = 0

client, address = s.accept() 
data = client.recv(size) 
if data == "spaceBar":
        spinSpeed = spinSpeed + 1
        spin.angV = [0, 0, spinSpeed]
        cont.activate(spin)

so, i run this and hooray, it doesn’t freeze, but . . . i keep getting this error:


Python script error - object 'Top', controller 'Python':
Traceback (most recent call last):
  File "spin.py", line 73, in &lt;module&gt;
  File "/Applications/Blender/blender.app/Contents/MacOS/2.71/python/lib/python3.4/socket.py", line 184, in accept
    fd, addr = self._accept()
BlockingIOError: [Errno 35] Resource temporarily unavailable

any thoughts on ‘resource temporarily unavailable’? thanks.

8

You’ve got two things holding up your script. The most obvious is the while loop since it’ll never finish. The second being the .accept call:
client, address = s.accept()
This will block the script until you get an incoming connection, which keep Blender frozen too.

I would suggest initializing the socket (‘s’) into a GameLogic variable (maybe GameLogic.socket). Then, create a function with your while loop and spawn it into a new thread. This function will take any network input and append it to a different GameLogic variable (something like GameLogic.socket_input). Then have a pulsing script that’ll check that GameLogic variable and do things if it finds any data.

9

[moderation]reopened for further contribution.

Please be aware this thread is originated from 2014!

10

Thanks monster. I believe I have a solution to the second problem - this error:

Python script error - object 'Top', controller 'Python':
Traceback (most recent call last):
  File "spin.py", line 73, in &lt;module&gt;
  File "/Applications/Blender/blender.app/Contents/MacOS/2.71/python/lib/python3.4/socket.py", line 184, in accept
    fd, addr = self._accept()
BlockingIOError: [Errno 35] Resource temporarily unavailable

Can be resolved by making the socket async (either using .settimeout(0), as theOtherHolmes did, or using .setblocking(0)), wrapping your .listen() in a try-except, and appending each new connection to a list like so:

try:
    newconnection=s.accept()
    connections.append(newconnection)
except:
    pass

Then iterate over all connections later -

for i in connections:
    do something for each player...

or something similar.

I also found when testing this that sometimes, when running two tests, one right after the other, the port I was using would still be allocated to the previous instance of the program, and I had to wait ~10sec for the OS to free it up again. I would get an error “Address already allocated” or something. To fix this, call .shutdown() on the port before the program closes.

11

You should avoid using a bare except clause, as you will catch potentially unintended errors.