How to receive data from UDP socket (over WiFi)

[nadvorvo]

Hi everyone,
I am trying to send UDP packet using GPy. For testing I am using service QOTD (djxmmx.net).
On my desktop python the code if functional, on GPy no data received.

Thank you in advance for your assistance.
Regards, Vojtech

code snipet from GPy

>>> uos.uname()
(sysname='GPy', nodename='GPy', release='1.20.2.r3', version='v1.11-d945d33ee on 2020-03-08', machine='GPy with ESP32',pybytes='1.3.1')

>>> wifi1.wlan.isconnected()
True
>>> import socket
>>> UDP_IP = "68.228.188.226"
>>> UDP_PORT = 17
>>> MESSAGE = b''
>>> s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
>>> s.settimeout(5)
>>> s.sendto(MESSAGE, (UDP_IP, UDP_PORT))
0
>>> data, address = s.recvfrom(1024)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TimeoutError: timed out
>>>

when do same from my desktop the code is successful:

>>> import socket
>>> UDP_IP = "68.228.188.226"
>>> UDP_PORT = 17
>>> MESSAGE = b''
>>> s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
>>> s.settimeout(5)
>>> s.sendto(MESSAGE, (UDP_IP, UDP_PORT))
0
>>> data, address = s.recvfrom(1024)
>>> print(data.decode())
"The secret of being miserable is to have leisure to bother about whether
 you are happy or not.  The cure for it is occupation."
 George Bernard Shaw (1856-1950)

[nadvorvo]

Hi @robert-hh,
I really appreciate the support you’ve given me. Thank you.
Also functional on my side.

Regards, Vojtech

[robert-hh]

@nadvorvo Update: on all devices this modified code works:

import socket
UDP_IP = "68.228.188.226"
UDP_PORT = 17
MESSAGE = b' '
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.settimeout(5)
print(s.sendto(MESSAGE, (UDP_IP, UDP_PORT)))

data, address = s.recvfrom(1024)
print(data.decode())

[robert-hh]

@nadvorvo So I could replicate your problem. Interestingly it also exists in different flavors on other micropython (non-pycom) variants and devices.
With Pycom MicroPython the receive fails.
On ESP32 and Winnermicro W600 ports the send returns a timeout error, but the following receive succeeds.
On ESP8266 and Pyboard UD is not supported.
Big mess.

BUT: if you do not send an empty message, but for instance a single space, it works. So there is a problem dealing with an empty packet.

[nadvorvo]

Hi @robert-hh,
Thank you for your reply. I am connected to same wifi network from both devices (desktop notebook, GPy). Router settings should not be problem.

[robert-hh]

@nadvorvo Could it be a setting of your internet router?