HELP - Program stuck at socket data recovering

[Stalketeer]

Hello. I need help with socket data send-receive in Python, on Raspberry Pi

I have 2 Raspberry Pi. No 2 is sending data to No 1. I speak into No 1 microphone, and No 1 will send data to No 2 when it detect my voice. No 2 will play a response sound using a .wav file.
There is absolutely no problem with No 1 - No 2 data transmission.

But I noticed that the loop will stuck at this line, until data is received from No 1.
dataByte, addr = sock.recvfrom(1024) # buffer size is 1024 bytes
Then the loop will continue, until it's stuck there again when there is no data received.

How can I make the loop progress, regardless of whether data is received or not?
How can I un-stuck the program loop from that socket waiting for data?

Thanks in advance. Any idea is appreciated.

This is the full code on the receiving Pi:

# receive.py
import time
import socket
import pprint
import pygame

soundstarttime = time.time()
soundendtime = time.time()
soundplaytime = time.time()
soundplaying = 0

#Initialise pygame and the mixer
pygame.init()
pygame.mixer.init()
#load the sound file
voicepath = pygame.mixer.Sound("/home/pi/Desktop/voice/yaaa.wav")
voicepath.play()

mainloop = 1
#---------------------------------------------------------------------------
UDP_IP = "192.168.1.5"
UDP_PORT = 5005

sock = socket.socket(socket.AF_INET, # Internet
                     socket.SOCK_DGRAM) # UDP
sock.bind((UDP_IP, UDP_PORT))

while mainLoop == 1:

    #while True:
    dataByte, addr = sock.recvfrom(1024) # buffer size is 1024 bytes
    dataString = dataByte.decode("utf-8")
    print("received message: ", dataString)

    #------------------------------------------------------------------------
    # PROBLEM!!!! loop stuck at sock.recvfrom(1024) if no data received by LAN

if dataString == "cibo":                       
            voicepath = pygame.mixer.Sound("/home/pi/Desktop/voice/yaaa.wav")
            voicepath.play()
#####################################################################

[Fourier]

Have a test/if check, if there is any data in sockets buffer.

[Stalketeer]

Err what command should I use to check for data in the socket buffer?

Update
I took out the SD card for backup, and after that it plays just fine np matter how many time I called aplay

[AtomiC]

I can't really help with python but "waiting/blocking until data is received" is usually intended behaviour. But usually there is a way to set the socket to be non-blocking.

https://docs.python.org/2/howto/sockets.html

Scroll down to the Non-blocking Sockets part. socket.setblocking(0) should be what you are looking for.

[Stalketeer]

Yep non blocking socket works. Can't find any downside from setting it to be non-blocking. Why would they made sockets to be blocking anyway is the first place?
Thank you guys.

[Fourier]

Sockets can run on separate threats, which can block anyway.