Exit Python While Loop when socket disconnects

Question

I have a bit of code that receives a WiFi password from a Raspberry Pi. The Pi dishes out a new code every 2 minutes. The script below checks the password and updates the connection with the new password if needed.

        # Create a TCP/IP socket

s=socket(AF_INET, SOCK_DGRAM)


# Bind the socket to the port
s.bind (('',4446))
s.settimeout(10.0)
print ("Listening . . . .")

data=s.recv(1024).decode()
print ("Password:  "+data)
os.system('netsh wlan set profileparameter name=PI_AP Keymaterial='+data)
var1=data

try:
    while 1:
        data=s.recv(1024).decode()
        print ("Password:  "+data)

        if var1!=data:
            os.system('netsh wlan set profileparameter name=PI_AP Keymaterial='+data)
            print ("Password:  "+data)
            var1=data

except socket.timeout:
    print ("Timed Out")

Here is the output, with the error message I am seeing after I disconnect:

>>> ================================ RESTART ================================
>>> 
Listening . . . .
Password:  m9FyvpJCILQrZB4sq125AfUn9nfS9Z6qDlbBxy12pL48y5kJTLrH01osp4xXWN3
Password:  m9FyvpJCILQrZB4sq125AfUn9nfS9Z6qDlbBxy12pL48y5kJTLrH01osp4xXWN3
Password:  m9FyvpJCILQrZB4sq125AfUn9nfS9Z6qDlbBxy12pL48y5kJTLrH01osp4xXWN3

**Traceback (most recent call last):
  File "C:\Users\cave\Desktop\system_V1\UAD-V1.0.py", line 21, in <module>
    data=s.recv(1024).decode()
socket.timeout: timed out

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\cave\Desktop\system_V1\UAD-V1.0.py", line 29, in <module>
    except socket.timeout:
TypeError: catching classes that do not inherit from BaseException is not allowed
>>>**

can't you have while data: instead?

Chuck
– Chuck

2016-03-12 15:24:33 +00:00
Commented Mar 12, 2016 at 15:24 — Chuck
– Chuck, Commented Mar 12, 2016 at 15:24

Bharel · Accepted Answer · 2016-03-12 16:43:06Z

1

You should receive a socket disconnection exception, or empty data (as you tested in the if) in case of a disconnection.

If you do not receive the exception (which is kinda awkward) you may use the select (low-level) or the selectors (high-level) modules in order to see if you receive data on the line.

You may set a 2 minute timeout which afterwards the select() function will throw an exception.

UPDATE:

In order to catch the timeout exception, wrap your code like this:

try:
    while 1:
        ...
except socket.timeout:
    print("timed out")
...

UPDATE 2:

Seems like you're trying to catch socket.socket.timeout while you need to catch socket.timeout. I believe you used this line on top: from socket import *. If so, try catching timeout and not socket.timeout. That's the reason from ... import * is not recommended.

edited Mar 12, 2016 at 16:43

answered Mar 12, 2016 at 15:35

Bharel

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6 Comments

Jimdog Over a year ago

thanks for the quick reply. I do get the exception: Traceback (most recent call last): File "C:\Users\cave\Desktop\system_V1\UAD-V1.0.py", line 23, in <module> s.recv(1024).decode() socket.timeout: timed out. but I am unsure of how to handle this in a way so that I exit the loop.

Jimdog Over a year ago

to test I used 'print ("Success") after the While looop. I saw the disconnect exception but NOT the 'Success' message.

Bharel Over a year ago

@Jimdog Updated answer.

Jimdog Over a year ago

Different error this time, but I can see it try and handle the exception in some way... Traceback (most recent call last): File "C:\Users\cave\Desktop\system_V1\UAD-V1.0.py", line 21, in <module> data=s.recv(1024).decode() socket.timeout: timed out During handling of the above exception, another exception occurred: Traceback (most recent call last): File "C:\Users\cave\Desktop\system_V1\UAD-V1.0.py", line 29, in <module> except socket.timeout: TypeError: catching classes that do not inherit from BaseException is not allowed

Bharel Over a year ago

I'm not entirely sure what happened there, could you edit your question with the updated script and exception? (Hard to see in the comments)

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