Why can't I send sockets while I have a kivy app?

So, I'm trying to make a mobile multiplayer game, but either the kivy app is not working, either the server's not working, depends on what I put first.

import socket
import time
import kivy
from kivy.app import App
from kivy.uix.label import Label
import pickle






def server():
    HEADERSIZE = 10

    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.bind((socket.gethostname(), 1243))
    s.listen(5)

    while True:
        pos = 3
        clientsocket, address = s.accept()
        print(f"Connection from {address} has been established.")

        msg = pickle.dumps(pos)
        msg = bytes(f"{len(msg):<{HEADERSIZE}}", 'utf-8') + msg
        print(msg)
        clientsocket.send(msg)
        clientsocket.close()

def app():
    class MyApp(App):
        def build(self):
            return Label(text='text')
    MyApp().run()

server()
app()

If I run this I can make a connection with another device, but the app's window doesn't shows. I realized that this is because the server has an infinite loop, so I tried the other way around, but I had the problem that the application was also an infinite loop, so I tried using multiprocessing.

import socket
import time
import kivy
from kivy.app import App
from kivy.uix.label import Label
import pickle
from multiprocessing import Process






def server():
    HEADERSIZE = 10

    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.bind((socket.gethostname(), 1243))
    s.listen(5)

    while True:
        pos = 3
        clientsocket, address = s.accept()
        print(f"Connection from {address} has been established.")

        msg = pickle.dumps(pos)
        msg = bytes(f"{len(msg):<{HEADERSIZE}}", 'utf-8') + msg
        print(msg)
        clientsocket.send(msg)
        clientsocket.close()

def app():
    class MyApp(App):
        def build(self):
            return Label(text='text')
    MyApp().run()


if __name__=='__main__':

    Process(target=app()).start()
    Process(target=server()).start()

But the same thing happens. How could I solve this?