I've been working on a game using a number of Raspberry Pis, Python, and some buttons/switches. My game requires a central server that issues commands to multiple clients.
I'm not new to programming but new to Python and lower-er level network communication and have been lost in the weeds for the past 2 days on how exactly to write my server code.
The client program is a simple socket.connect and then waits for data to be sent. No problems there.
I have had a tough time determining exactly how to write and how to make work the server.
Here's what my server code looks like at the moment:
import socket, time, sys
import threading
TCP_IP = ''
TCP_PORT = 8888
BUFFER_SIZE = 1024
CLIENTS = {}
clientCount = 0
def listener():
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((TCP_IP,TCP_PORT))
s.listen(5)
while True:
conn, addr = s.accept()
print("new connection from:"+ str(addr))
#print(len(CLIENTS))
global clientCount
clientCount = clientCount+1
print (clientCount)
# register client
CLIENTS[conn.fileno()] = conn
def broadcast():
for client in CLIENTS.values():
client.send('this is a broadcats msg')
if __name__ == '__main__':
listener()
while clientCount > 0:
broadcast()
print(len(CLIENTS)) #print out the number of connected clients every 5s
time.sleep(5)
Here's the desired flow:
1. Server starts and waits for first connection or more. I believe this "Server" should be running on a background thread?
2. If connectionCount > 0 start the main program loop
3. For now the main program loop should just display the number of connected clients and broadcast a message to all of them every 5 seconds.
I have about 5 versions of this server. I have tried async, select.select, and several threaded approaches but can't quite nail down the behavior I seek. Should I be putting the server in a background thread? If so how to broadcast to all the connections?
The only thing I haven't tried is Twisted and that is because I could not get it installed in Windows... so I'm ruling that optino out for the moment. If anyone has a pointer on where to go on this I would really appreciate it!
Update
Ok, based on @Armans suggestion I have updated my code so that there is a server class but it still performs the same.
class server():
def __init__(self):
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((TCP_IP,TCP_PORT))
s.listen(10)
while 1:
client_socket, addr = s.accept()
print ('Connected with ' + addr[0] + ':' + str(addr[1]))
global clientCount
clientCount = clientCount+1
print (clientCount)
# register client
CLIENTS[client_socket.fileno()] = client_socket
threading.Thread(target=self.handler, args=(client_socket, addr)).start()
def handler(self, client_socket, addr):
while 1:
data = client_socket.recv(BUFFER_SIZE)
print ('Data : ' + repr(data) + "\n")
data = data.decode("UTF-8")
def broadcast(self, message):
for c in self.CLIENTS:
c.send(message.encode("utf-8"))
if __name__ == '__main__':
s = server() #create new server listening for connections
while clientCount > 0:
s.broadcast('msg here')
print(len(CLIENTS)) #print out the number of connected clients every 5s
time.sleep(5)
I can connect multiple clients and the console displays the following:
Connected with 10.0.0.194:38406
1
Connected with 10.0.0.169:36460
2
But the code in the "while clientCount" loop never runs. This is the zone where I have been stuck for some time so if you have a couple more ideas I would love to here any ideas!
2 Answers 2
Finally got it working! Much thanks to @Arman for pointing me in the right direction with the threading. I finally feel like I understand how everything is working!
Here is my complete Server & Client code. Hopefully this helps someone else with a master> client setup. The _broadcast() function is working as you will see it just broadcasts a static msg at the moment but that should be an easy update.
If anyone has any advice on code cleanup, python best practices using this code as the sample I would love to hear and learn more. Thanks again SE!
##Client
import socket
import sys
import json
#vars
connected = False
#connect to server
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_socket.connect(('10.0.0.158',8888))
connected = True
while connected == True:
#wait for server commands to do things, now we will just display things
data = client_socket.recv(1024)
cmd = json.loads(data) #we now only expect json
if(cmd['type'] == 'bet'):
bet = cmd['value']
print('betting is: '+bet)
elif (cmd['type'] == 'result'):
print('winner is: '+str(cmd['winner']))
print('payout is: '+str(cmd['payout']))
##Server
import socket, time, sys
import threading
import pprint
TCP_IP = ''
TCP_PORT = 8888
BUFFER_SIZE = 1024
clientCount = 0
class server():
def __init__(self):
self.CLIENTS = []
def startServer(self):
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((TCP_IP,TCP_PORT))
s.listen(10)
while 1:
client_socket, addr = s.accept()
print ('Connected with ' + addr[0] + ':' + str(addr[1]))
global clientCount
clientCount = clientCount+1
print (clientCount)
# register client
self.CLIENTS.append(client_socket)
threading.Thread(target=self.playerHandler, args=(client_socket,)).start()
s.close()
except socket.error as msg:
print ('Could Not Start Server Thread. Error Code : ') #+ str(msg[0]) + ' Message ' + msg[1]
sys.exit()
#client handler :one of these loops is running for each thread/player
def playerHandler(self, client_socket):
#send welcome msg to new client
client_socket.send(bytes('{"type": "bet","value": "1"}', 'UTF-8'))
while 1:
data = client_socket.recv(BUFFER_SIZE)
if not data:
break
#print ('Data : ' + repr(data) + "\n")
#data = data.decode("UTF-8")
# broadcast
for client in self.CLIENTS.values():
client.send(data)
# the connection is closed: unregister
self.CLIENTS.remove(client_socket)
#client_socket.close() #do we close the socket when the program ends? or for ea client thead?
def broadcast(self, message):
for c in self.CLIENTS:
c.send(message.encode("utf-8"))
def _broadcast(self):
for sock in self.CLIENTS:
try :
self._send(sock)
except socket.error:
sock.close() # closing the socket connection
self.CLIENTS.remove(sock) # removing the socket from the active connections list
def _send(self, sock):
# Packs the message with 4 leading bytes representing the message length
#msg = struct.pack('>I', len(msg)) + msg
# Sends the packed message
sock.send(bytes('{"type": "bet","value": "1"}', 'UTF-8'))
if __name__ == '__main__':
s = server() #create new server listening for connections
threading.Thread(target=s.startServer).start()
while 1:
s._broadcast()
pprint.pprint(s.CLIENTS)
print(len(s.CLIENTS)) #print out the number of connected clients every 5s
time.sleep(5)
Comments
I have a multithread approach here :
s.listen(10)
while 1:
client_socket, addr = s.accept()
print ('Connected with ' + addr[0] + ':' + str(addr[1]))
threading.Thread(target=self.handler, args=(client_socket, addr)).start()
def handler(self, client_socket, addr):
while 1:
data = client_socket.recv(BUFF)
print ('Data : ' + repr(data) + "\n")
data = data.decode("UTF-8")
I strongly recommend you two write a class for Server and Client, for each client create a Client object and connect it to Server, and store each connected Client (its socket and a name for example) to a dictionary as you did, then you want to broadcast a message you can go through all connected Clients in Server and broadcast message you want like this:
def broadcast(self, client_socket, message):
for c in self.clients:
c.send(message.encode("utf-8"))
Update
Because you have a thread that runs main you need another thread for running server , I suggest you write a start method for server and call it in a thread :
def start(self):
# all server starts stuff comes here as define socket
self.s.listen(10)
while 1:
client_socket, addr = self.s.accept()
print ('Connected with ' + addr[0] + ':' + str(addr[1]))
threading.Thread(target=self.handler, args=(client_socket, addr)).start()
now in main section or main file after create server object run the start thread :
a = server()
threading.Thread(target=a.start).start()