MicroPython Forum (Archive)

Hi,

I'm new to MicroPython and a bit new to Python too. I'm trying to send data using sockets to an ESP8266. I want the ESP8266 to be the server and my pc to be the client but I get an error when trying to receive data and I can't find any helpfull documentation to help me in this case.

This is my code:
[code]
import machine
import network
import socket

p = machine.Pin(2, machine.Pin.OUT)

p.low()

print('connecting to network...')

sta_if = network.WLAN(network.STA_IF)

ap_if = network.WLAN(network.AP_IF)

if (ap_if.active()):
ap_if.active(False)

sta_if.active(True)
sta_if.connect('MY_AP','PASSWORD')

while not sta_if.isconnected():
pass
print('network config:', sta_if.ifconfig())
ips = sta_if.ifconfig()


def server_init():
s = socket.socket()
s.bind( ('', 3266) )
s.listen(1)
c, a = s.accept()
time.sleep(5)
while True:
data= s.recv()
print(dato)


server_init()

[/code]


It connects to the ap perfectly and when I try to connect using nc 192.168.1.133 3266, it accepts and then it fails. in the data = s.recv() line.


I try to reproduce the error using repl and when I get to the s.recv() line I get:


Traceback (most recent call last):
File "<stdin>", line 1, in <module>
OSError: 0

It just fails.

Can anyone give me any hints?

Thank you.

Are you sure that these two lines are in your code?
The second line should fire an error, unless your codes says:

Hi Roberthh

Yes, they are.

It even throws an error when I try it via repl directly.

So that's how my test code looks like: Edit: Simplified to you base code

Hi,

Thank you very much. My problem was that I was using the socket (s) with the recv method instead of the client (c).

Now it works but I think documentation is not right then:

https://docs.micropython.org/en/latest/ ... k_tcp.html
http://docs.micropython.org/en/latest/w ... ocket.send

Right?

Or am I missing something?

Thank you very much.

Hi @Twistx77. The example you point at shows a client, which opens a connection to a server, while you code creates a server which accepts connections opened by a client.

Twistx77 wrote:Hi,

Thank you very much. My problem was that I was using the socket (s) with the recv method instead of the client (c).

Now it works but I think documentation is not right then:

https://docs.micropython.org/en/latest/ ... k_tcp.html
http://docs.micropython.org/en/latest/w ... ocket.send

Right?

Or am I missing something?

Thank you very much.

You can only call send and recv against a connected socket and a listening socket is not connected to anything.

If a server listens on 192.168.1.1:5000 and a client connects to that address/port combination the server will create a new socket on 192.168.1.1:<random_port_number> and connect the client to it. This is transparent to the client which sees it as a connection on port 5000 but from a server perspective the port (and therefore socket) the client connected to is not the one that actually gets connected and carries the data.

Thanks to both for the clarification.

I understand now what my problem is.

I couldn't find an example of my case so I hope this helps someone else .

Once again thanks again to both.