Python script doesn't continue execution after creating thread

Question

i'm trying to write a socket-server program to send keyboard inputs from my PC to my Raspberry Pi, but when i create a new thread for a function, that has a while loop in it, the script execution does not continue as expected, instead it is stuck. These are my scripts:

import socket
import threading

class Server:
    def __init__(self, host: str, port: int):
        self.host = host
        self.port = port
        self.server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.server.bind((host, port))
        self.server.listen()
        self.client = None
        self.message = ""

    def stream(self):
        while True:
            self.client.send(self.message.encode('utf-8'))

    def run(self):
        while True:
            print('Server is running and listening ...')
            self.client, address = self.server.accept()
            print(f'Connection is established with {str(address)}')
            thread = threading.Thread(target=self.stream)
            thread.start()

from server import Server
import threading

server = Server('192.168.178.30', 8001)
thread = threading.Thread(target=server.run)
thread.start()

while True:
    try:
        print("A")
    except KeyboardInterrupt:
        break

When i executed the second program it didn't output A's, instead only executed, what's in the while loop of the run function of the first script.

Mark Tolonen · Accepted Answer · 2024-02-06 20:28:00Z

The code works with localhost, but has a few things that need correcting to handle clients properly:

server.py

import socket
import threading
import time

class Server:
    def __init__(self, host: str, port: int):
        self.host = host
        self.port = port
        self.server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.server.bind((host, port))
        self.server.listen()
        # self.client = None  # not needed.  Need a local client per client thread
        # self.message = ""   # not needed.  Sending a hard-coded message below.

    def stream(self, client, address):  # add arguments
        print(f'Connection is established with {address}')
        while True:
            client.send(b'hello\n')  # Send an actual message
            time.sleep(1)            # Slow things down for demo

    def run(self):
        while True:
            print('Server is running and listening ...')
            client, address = self.server.accept()  # local client value
            # pass arguments to thread
            thread = threading.Thread(target=self.stream, args=(client, address))
            thread.start()

test.py

from server import Server
import threading
import time

server = Server('', 8001)
thread = threading.Thread(target=server.run)
thread.start()

while True:
    try:
        print('.', end='', flush=True)  # Less noisy
        time.sleep(1)                   # slow down for demo
    except KeyboardInterrupt:
        break

Connecting demo:

>>> import socket
>>> s=socket.socket()
>>> s.connect(('localhost', 8001))
>>> s.recv(1024)
b'hello\nhello\nhello\nhello\n'
>>> s.recv(1024)
b'hello\n'

Output from test.py:

C:\>test
Server is running and listening ...
........Connection is established with ('127.0.0.1', 39750)
Server is running and listening ...
...................

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