I have a really short and easy question:
How to invoke the send() method from another python file/class? I want to send a message from another component to client (connection is established).
I thought Ijust have to get the reference of the singleton instance and then just "send" like this:
server = Server(ip,port)
server.send("hello")
If I do it like that, I get the error:
NoneType' object has no attribute 'send'
Maybe "self" is here the problem...
here is the server class:
class Server(threading.Thread):
##############################################################################
# Server: Singleton Instance
##############################################################################
_instance = None
def __new__(cls, *args, **kwargs):
if not cls._instance:
cls._instance = super(Server, cls).__new__(cls, *args, **kwargs)
return cls._instance
##############################################################################
# Constructor of Server
##############################################################################
def __init__(self, host, port):
threading.Thread.__init__(self)
print "[SERVER____] Creating Server Thread"
self.host = host
self.port = port
self.__reset__()
##############################################################################
# Resetting local attributes
##############################################################################
def __reset__(self):
print "[SERVER____] Reset"
self.serverSock = None
self.clientSock = None
self.clientAddr = None
self.clientData = None
self.isRunning = None
self.isWaiting = None
###########################################################################
def send(self, message):
print "[SERVER____] Sending Message", message
self.clientSock.send(message)
##############################################################################
# Stop the Server: Close the Socket and Reset
##############################################################################
def stop(self):
# Close The Client Socket
if(self.clientSock):
self.clientSock.close()
print "[SERVER____] Aborting Client Socket"
# Close The Server Socket
if(self.serverSock):
self.serverSock.close()
print "[SERVER____] Aborting Server Socket"
# Reset the Member Fields
self.__reset__()
print "[SERVER____] Aborting Server Thread"
self._Thread__stop()
##############################################################################
# Server.start()
##############################################################################
def run(self):
try:
# Create The Socket
self.serverSock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print "[SERVER____] Creating Server Socket"
# Set Socket Options
#self.serverSock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1);
# Bind The New Socket
self.serverSock.bind((self.host, self.port))
print "[SERVER____] Binding Server Socket"
print "[SERVER____] IP: ", self.host, " Port: ", self.port
# Set The Awaiting Flag
self.isWaiting = True;
# Start The Server Loop
while self.isWaiting:
# Listen On New Socket
self.serverSock.listen(1)
print "[SERVER____] Listening Server Socket"
# Accept New Connection
self.clientSock, self.clientAddr = self.serverSock.accept()
print "[SERVER____] Accepting New Connection: " , self.clientAddr
# Set The Running Flag
self.isRunning = True;
# Serve The Connection
while self.isRunning:
print "[SERVER____] Want to recv message...."
try:
# Receive A New Data Block
self.clientData = self.clientSock.recv(config.BUFFERSIZE)
# Process The New Data Block
if not self.clientData:
print "[SERVER____] Reset By Client Connection"
break
else:
print "[SERVER____] Receiving Message: ", self.clientData
parser = MessageParser()
parser.parseSMMessage(self.clientData)
except socket.error:
print "[SERVER_ERR] Error at receiving data from client."
except Exception as exc:
print "[SERVER____] Server Thread Exception ", exc
Your implementation of the singleton pattern is wrong, and this causes self.clientSock to be set to None before calling self.clientSock.send. The implementation is wrong because it will call __init__ each time you get the singleton instance. Basically, what happens is:
Server(...) to get the instance.run is called on that instance. This sets self.clientSock.Server(...) to get the instance again. This will return the same instance due to your implementation of __new__, but __init__ will be called on it again and self.clientSock will be reset to None.self.clientSock.send causes an exception.I recommend avoiding using __new__ to implement a singleton if you need one (though not using a singleton at all is probably best). Some other methods are listed here.
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