[Twisted-Python] Writing a plug-in for an online game that uses UDP

[Jp Calderone]

Ibrahim Mubarak wrote:
> Hi,
> 
> [snip]
>     def sendingOutput(self, result, host, port):
>         """
>             A callback for the deferred object returned
>         """
>         self.transport.write(str(result) + "\n" + str(self) + "\n", (host, port))
>         return
>     
>     def datagramReceived(self, data, (host, port)):
>         msg = data.split()
>         if len(msg) != 1 and len(msg) != 3:
>             self.sendingOutput("error" , host, port)
>             return
>         
>         if msg[0] == "log" and len(msg) == 3:
>             user = msg[1]
>             pswd = msg[2]
>             self.iiwuservice.logUser(user, pswd, host, port).addCallback(self.sendingOutput(self,
> host, port))

   The above line is a problem.  I believe you want it to read:

     self.iiwuservice.logUser(user, pswd, host, port
         ).addCallback(self.sendingOutput, host, port
         )

   You cannot put self.sendingOutput(self, host, port) directly in the 
arguments list, because Python would treat it like any other function 
call: call it, and then use the return value as the argument to 
addCallback().  In general,

     d.addCallback(f, *a, **kw)

   will lead to Twisted invoking f like this:

     f(result, *a, **kw)

   where result is the value with which the Deferred eventually fires.

   Jp