Re: Sockets
- From: Jp Calderone <exarkun@xxxxxxxxxx>
- Date: Thu, 05 May 2005 13:19:21 GMT
On Thu, 05 May 2005 17:11:08 +0800, Dan <dan@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
I have a problem and I don't quite know how to implement the solution.
I'll have a server application that will listen on a tcp port and make many similtaneous connections to remote clients. From time to time, I'll need to write a small amount of data on one of those sockets. A notification to write to one of the sockets will come from another program/process.
I think that the best way to send the notification to this server application is via a udp message. Alternatively, I could use tcp, but I don't think I'll need the extra complexity for what I want to do. (Other suggestions welcome.)
UDP is actually more complex than TCP. I recommend sticking with TCP until you have a better reason (eg, you need to communicate simultaneously with tens of thousands of clients).
The server application will multiplex the connections using 'select', so much of the time it will be blocked on 'select'.
My problem is how to also listen on a udp port while the process is blocked by 'select'. Should I run a separate thread? And if so can I share the socket connection across the two threads? (Thread 1 will be accepting client connections, thread 2 will we writing data to it.) Or should I simply let 'select' time out after some period?
I'm a bit lost as to how to do this, I hope someone can put me on the right track. Any solution that I use should be applicable on Linux and Windows platforms.
I recommend using Twisted. Here's a sample application that accepts connections, waits on messages from each client, and then transmits another message to all other clients in response to receiving one (untested code):
from twisted.internet import reactor, protocol from twisted.protocols import basic
# Define the protocol with which we will handle all # incoming connections
class ClientMessageProtocol(protocol.LineReceiver):
# When a connection is established, append this # instance to the factory's list of connected # clients, so it can send messages to this client # when necessary.
def connectionMade(self):
self.factory.clients.append(self)
# Likewise, remove the instance when the connection # is lost.
def connectionLost(self):
self.factory.clients.remove(self)
# Every time a whole line is received, tell the factory # about it.
def lineReceiver(self, line):
self.factory.lineReceived(self, line)
class ClientMessageFactory(protocol.ServerFactory):
# Indicate the protocol to be instantiated for each
# connection to this factory.
protocol = ClientMessageProtocol # At startup, make an empty clients list.
def startFactory(self):
self.clients = [] # Whenever a client tells us they received a line, send
# a short message to every other connection client.
def lineReceived(self, client, line):
for cl in self.clientz:
if cl is not client:
cl.sendLine("%s sent me a message: %r" % (client, line))# Start the server on TCP port 54321 reactor.listenTCP(54321, ClientMessageFactory())
# Run the main event loop reactor.run()
Learn more about Twisted on its website: http://www.twistedmatrix.com/
Jp .
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- Sockets
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