Script that sets up a server to accept connections and a client to flood the server with connections.

tcp_conn_blaster.py

import logging
import socket
import sys
import threading
import time

CLIENT_CONN_ADDR="127.0.0.1"
CLIENT_NUM_CONNS=10
SERVER_PORT=8888
SERVER_SYN_BACKLOG=128
SERVER_WAIT_BEFORE_CLOSE=True
SERVER_WAIT_BEFORE_CLOSE_SECS=3
HELP_MESSAGE="Please specify either \"server\" or \"client\" as an argument."

def handle_client_conn(conn, addr):
    try:
        logging.info("Handling new client connection from %s:%d" % (addr[0], addr[1]))
        if SERVER_WAIT_BEFORE_CLOSE:
            time.sleep(SERVER_WAIT_BEFORE_CLOSE_SECS)
        logging.info("Closing connection to %s:%d" % (addr[0], addr[1]))
        conn.close()
    except Exception as e:
        logging.error("Error handling connection %s: %s" % (addr, e))

def conn_to_server():
    try:
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        logging.info("Connecting to server %s..." % (CLIENT_CONN_ADDR))
        start_time = time.time()
        sock.connect((CLIENT_CONN_ADDR, SERVER_PORT))
        end_time = time.time()
        conn_time = end_time - start_time
        logging.info("New connection took %.4f seconds" % conn_time)
        logging.info("Succesful connection to server.")
        sock.close()
    except Exception as e:
        logging.error("Error connection to server: %s" % e)

def main():
    if len(sys.argv) != 2:
        print(HELP_MESSAGE)
        return

    if sys.argv[1] == "client":
        server = False
    elif sys.argv[1] == "server":
        server = True
    else:
        print(HELP_MESSAGE)
        return

    logging.basicConfig(level=logging.DEBUG)
    threads = []

    if server:
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.bind(("0.0.0.0", SERVER_PORT))
        sock.listen(SERVER_SYN_BACKLOG)
        logging.info("Server now listening on 0.0.0.0:%d..." % SERVER_PORT)
        while True:
            try:
                conn, addr = sock.accept()
                thread = threading.Thread(target=handle_client_conn, args=(conn, addr))
                threads.append(thread)
                thread.start()
            except Exception as e:
                logging.error("Failed to handle connection %s with error %s" % (addr, e))
            except KeyboardInterrupt:
                logging.info("Got Ctrl-C, killing threads")
                for t in threads:
                    t.kill_received = True
                sock.close()
                return
    else:
        num_of_conns = 0
        try:
            while True:
                try:
                    if num_of_conns >= CLIENT_NUM_CONNS:
                        logging.info("Hit maximum number of client connections outgoing, sleeping.")
                        break
                    else:
                        thread = threading.Thread(target=conn_to_server)
                        threads.append(thread)
                        thread.start()
                        num_of_conns = num_of_conns + 1
                except Exception as e:
                    logging.error("Failed to connect to server: %s" % e)
            while True:
                    time.sleep(10)
        except KeyboardInterrupt:
            logging.info("Got Ctrl-C, killing threads")
            for t in threads:
                t.kill_received = True
            return

if __name__ == "__main__":
    sys.exit(main())