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Hello! I’m doing a server/ client schema program in Python in which I wanted to have only one server and several clients.
Imagine having 3 clients each make a request to the server via socket connection, how is it that:
1: The server could accept more than one socket connection at the same time?
2: The server would perform the tasks (had thought of a database to store the requests and serve as cache)
Thank you!
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The answer to your first point is "yes", the server can accept and process more than one connection we have is to prepare it for that.
In this example the server can handle a single connection, but by grabbing it we can implement support for multiple connections, we will have to implement threads, where each connection on the server is a thread/processo "independent".
Below is a simple example of a chat server, commented where I think it should be explained:
Server:
import socket, threading
def run(conn):
while True:
data = conn.recv(1024) # receber informacao
if not data: # se o cliente tiver desligado
conns.remove(conn)
break
for c in conns: # enviar mensagem para todos os outros clientes
if c is not conn: # excepto para o que a enviou
c.send('{}: {}'.format(conn.getpeername(), data.decode()).encode('utf-8'))
conns = set() # armazenar conxoes aqui
host, port = ('', 9999)
with socket.socket() as sock: # ligacao TCP
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) # reutilizar endereco logo a seguir a fechar o servidor
sock.bind((host, port))
sock.listen(5) # servidor ativo
print('Server started at {}:{}\n'.format(host, port))
while True:
conn, addr = sock.accept() # esperar que alguem se conect
conn.send('WELCOME {}'.format(addr).encode())
conns.add(conn) # adicionar conexao ao nosso set de coneccoes
threading.Thread(target=run, args=(conn,)).start() # esta coneccao vai ser independente das outra a partir de agora, vamos correr a thread na funcao run
Client:
import socket, threading, sys, select
with socket.socket() as s:
s.connect(('', 9999))
while True:
io_list = [sys.stdin, s]
ready_to_read,ready_to_write,in_error = select.select(io_list , [], [])
for io in ready_to_read:
if io is s: # se tivermos recebido mensagem
resp = s.recv(1024)
if not resp:
print('server shutdown')
sys.exit()
print('{}'.format(resp.decode()))
else:
msg = sys.stdin.readline() # vamos enviar mensagem
s.send(msg.encode())
sys.stdout.flush()
As for your point 2 also gives, although I don’t quite understand what you want to store in the database.
If you want to save the connections you can for example (in this example I will store in a file), add this below the last line (threading.Thread(...) of the server example I put on top:
...
with open('conns.txt', 'a') as f:
f.write('{}\n'.format(':'.join(addr)))
It helped a lot! Thanks for the explanation and the provided code examples!
From @Hiperbolt, thank goodness
Just one additional question, the function Sock.Accept() returns two arguments, in this case Conn and addr. Conn corresponds to what exactly? (I’m just checking that I’m getting it all)
It does not return two, it returns a tuple, ex: (connection, ('213.32.12.2', 4324)), we do the unpacking, in which connection is the connection itself, it is with it that your server will work, to send messages, close etc... for example instead of conn, addr = sock.accept() , you could just dados_conn = sock.accept() in which dados_conn[0] would be your connection and dados_conn[1] is the address of the
Got it, thanks again
Dispõe @Hiperbolt
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– Woss
When you give a Listen on an IP/Port, each new connection creates a new socket. Just go storing these sockets in a list whenever you have a new connection (without blocking) and then loop around the list and collecting the data of each one. Finally, it is good to release the CPU before closing the main loop. By doing non-blocking, you will be managing multiple connections at the same time. The secret is only to take an action when in any of the data captures contain a complete command to be answered. For a more objective answer, it is better to divide doubt into separate questions.
– Bacco
@Bacco Thanks for the explanation, there is some site where I could see an example of code to better understand?
– hiperbolt
I don’t know if this helps: https://pymotw.com/2/socket/tcp.html (I just looked over it, it’s something a little simpler than what I said, but maybe it serves as a basis). I don’t normally use Python on a day-to-day basis (but socket is similar in most languages).
– Bacco