Python - TCP server, connection closed by remote host

Question

I want to write a simple client/server application in Python to send and receive JSON objects. The server is running fine and receives input from the client-side:

λ python server.py
Server running on localhost:9091
Handle request from ('127.0.0.1', 50877)
Received command: {'command': 'hello'}
Sent reply: {'ok': True}

On the client-side im getting the following output:

λ python client.py 
Socket created
Socket connected to ('localhost', 9091)
Sent message {'command': 'hello'} to ('localhost', 9091)
Traceback (most recent call last):
  File "C:\Users\Admin\Sample\client.py", line 25, in 
<module>
    connection.send_request(req)
  File "C:\Users\Admin\Sample\client.py", line 19, in 
send_request
    reply = json.load(fp=socket_input)
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\json\__init__.py", line 293, in load
    return loads(fp.read(),
  File "C:\Users\Admin\AppData\Local\Programs\Python\Python39\lib\socket.py", line 704, in readinto
    return self._sock.recv_into(b)
ConnectionResetError: [WinError 10054] An existing connection was forcibly closed by the remote host

Client

import json
import socket


class ServerConnection:
    def __init__(self, host: str, port: int):
        self._host = host
        self._port = port

    def send_request(self, request: any) -> str:
        with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
            sock.connect((self._host, self._port))
            print(f"Connected to {(self._host, self._port)}")
            sock.sendall(bytes(json.dumps(request), "utf-8"))
            sock.shutdown(socket.SHUT_WR)
            print(f"Sent message {request} to {(self._host, self._port)}")
            with sock.makefile(mode="r", encoding="utf-8") as socket_input:
                reply = json.load(fp=socket_input)
            print(f"Received: {reply}")


req = {"command": "hello"}
connection = ServerConnection("localhost", 9091)
connection.send_request(req)

Server

import io
import json
import socketserver


host: str = "localhost"
port: int = 9091


class RequestHandler(socketserver.StreamRequestHandler):
    def send_reply(self, reply: any):
        json.dump(
            obj=reply,
            fp=io.TextIOWrapper(self.wfile, encoding="utf-8"),
            sort_keys=True,
        )
        print(f"Sent reply: {reply}")

    def handle(self) -> None:
        print(f"Handle request from {self.client_address}")

        command = json.load(
            fp=io.TextIOWrapper(self.rfile, encoding="utf-8"),
        )
        print(f"Received command: {command}")

        reply = {"ok": True}
        self.send_reply(reply)


class Server(socketserver.TCPServer):
    def __init__(self, server_address):
        super().__init__(
            server_address=server_address,
            RequestHandlerClass=RequestHandler,
            bind_and_activate=True,
        )
        self._active = True

    def shutdown(self) -> None:
        self._active = False

    def continue_handling(self) -> bool:
        return self._active


with Server(
    server_address=(host, port),
) as server:
    print(f"Server running on {host}:{port}")
    while server.continue_handling():
        server.handle_request()
    print(f"Server shut down on {host}:{port}")

I would like to understand why this happens. After researching for a bit I found these possible reasons:

• Running out of system resources (unlikely)
• Too many requests to the server (it's just a single request here, unlikely)
• Firewall problems (I tried turning my firewall off temporarily)

I would be very grateful if someone spots a possible error in my code or points out what parts of my system configuration might be responsible for this behavior.