[Twisted-Python] data update to multiple clients

[Phil Mayers]

On 04/05/2010 12:39 PM, Chris Cusack wrote:
> Probably another newbie question but after much effort I am not
> progressing on the following.
>
> I am trying to design a system where I have a microprocessor
> periodically feeding data on a serial connection to a server script. I
> would then like the server script to notify one or more client scripts
> of the changed data across a local network. I have tried a few simple
> tcp server and client script examples which communicate well for a
> single call but do not seem to suit my application which is not client
> event driven. I considered having each client connect to the server
> every ?? seconds to query for new data but there may be a better way.

Perhaps I'm misunderstanding, but it's pretty simple. Just have the 
clients connect & stay connected. Keep a list of currently connected 
clients somewhere (see below) and every time you receive data on the 
serial port, write it out to all the clients. For example:

# ack, global variable!
client_list = []

class MyProtocol(Protocol):
   def connectionMade(self):
     client_list.append(self)

   def connectionLost(self, reason):
     if self in client_list:
       client_list.remove(self)

   def notifyClient(self, data):
     # you will probably want some framing here e.g. Netstring, len+data
     self.transport.write(data)

class ServerProto(Protocol):
   def dataReceived(self, data):
     for cli in client_list:
       cli.notifyClient(data)

...or am I misunderstanding you?