multicon-client.py

import sys
import socket
import selectors
import types


sel = selectors.DefaultSelector()

messages = [b'message 1 from client.', b'message 2 from client.']



def start_connections(host, port, num_conns):

	server_addr = (host, port)

	for i in range(0, num_conns):
		
		connid = i + 1
		print("starting connection: ", connid, "to", server_addr)

		sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

		sock.setblocking(False)

		sock.connect_ex(server_addr)

		events = selectors.EVENT_READ | selectors.EVENT_WRITE

		data = types.SimpleNamespace(
			connid=connid,
			msg_total=sum(len(m) for m in messages),
			recv_total=0,
			messages=list(messages),
			outb=b''
		)

		sel.register(sock, events, data=data)


def service_connection(key, mask):

	sock = key.fileobj
	data = key.data

	if mask & selectors.EVENT_READ:
		recv_data = sock.recv(1024)

		if recv_data:
			print("received: ", repr(recv_data), " from connection: ", data.connid)
			data.recv_total += len(recv_data)

		if not recv_data or data.recv_total == data.msg_total:
			print("closing connection to: ", data.connid)
			sel.unregister(sock)
			sock.close()

	if mask & selectors.EVENT_WRITE:

		if not data.outb and data.messages:
			data.outb = data.messages.pop(0)

		if data.outb:

			print("sending: ", repr(data.outb), "to connection: ", data.connid)
			sent = sock.send(data.outb)
			data.outb = data.outb[sent:]



if len(sys.argv) != 4:
	print("usage: ", sys.argv[0], "<host> <port> <num_connections>")
	sys.exit(1)

host, port, num_conns = sys.argv[1:4]

start_connections(host, int(port), int(num_conns))

try:
	while True:
		events = sel.select(timeout=None)

		if events:
			for key, mask in events:
				service_connection(key, mask)

		if not sel.get_map():
			break

except KeyboardInterrupt:
	print("caught keyboard interrupt")

finally:
	sel.close()