netcat in python

netcat.py

import socket
import socketserver
import threading

def sender(hostname, port, content):
    """Connect to a TCP port and send content, then wait for reply
    """
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
        sock.connect((hostname, port))
        sock.sendall(content)
        print("Sent {}".format(content))
        sock.shutdown(socket.SHUT_WR)
        while 1:
            data = sock.recv(1024)
            if data == "":
                break
            print("Received:", repr(data))
        print("Connection closed.")

class ServerHandler(socketserver.StreamRequestHandler):
    """Syntax sugar to avoid socket.bind, socket.listen, and socket.accept calls
    """
    def handle(self):
        """Deal with the TCP socket at self.request once a client has connected. Echo back what is received in uppercase"""
        data = self.rfile.readline().strip()
        print("{}: {}".format(self.client_address[0], repr(data)))
        self.wfile.write(data.upper())

def main(host, port):
    try:
        with socketserver.TCPServer((host, port), ServerHandler) as server:
            server.serve_forever()
    except KeyboardInterrupt:
        print("Server shutdown")

if __name__ == "__main__":
    import sys
    import random
    if sys.argv[1:2] == ["server"]:
        main("", 9999)
    elif sys.argv[1:2] == ["client"]:
        N = 30
        data = ''.join(random.choices(string.ascii_uppercase + string.ascii_lowercase + " " + string.digits, k=N))
        sender("localhost", 9999, data.encode("utf-8"))
    else:
        print("need command line argument 'server' or 'client'")