doc/core/howto/listings/pb/trap_client.py

   1 #!/usr/bin/env python
   2
   3 # Copyright (c) Twisted Matrix Laboratories.
   4 # See LICENSE for details.
   5
   6 from twisted.spread import pb, jelly
   7 from twisted.python import log
   8 from twisted.internet import reactor
   9
  10 class MyException(pb.Error): pass
  11 class MyOtherException(pb.Error): pass
  12
  13 class ScaryObject:
  14     # not safe for serialization
  15     pass
  16
  17 def worksLike(obj):
  18     # the callback/errback sequence in class One works just like an
  19     # asynchronous version of the following:
  20     try:
  21         response = obj.callMethod(name, arg)
  22     except pb.DeadReferenceError:
  23         print " stale reference: the client disconnected or crashed"
  24     except jelly.InsecureJelly:
  25         print " InsecureJelly: you tried to send something unsafe to them"
  26     except (MyException, MyOtherException):
  27         print " remote raised a MyException" # or MyOtherException
  28     except:
  29         print " something else happened"
  30     else:
  31         print " method successful, response:", response
  32
  33 class One:
  34     def worked(self, response):
  35         print " method successful, response:", response
  36     def check_InsecureJelly(self, failure):
  37         failure.trap(jelly.InsecureJelly)
  38         print " InsecureJelly: you tried to send something unsafe to them"
  39         return None
  40     def check_MyException(self, failure):
  41         which = failure.trap(MyException, MyOtherException)
  42         if which == MyException:
  43             print " remote raised a MyException"
  44         else:
  45             print " remote raised a MyOtherException"
  46         return None
  47     def catch_everythingElse(self, failure):
  48         print " something else happened"
  49         log.err(failure)
  50         return None
  51
  52     def doCall(self, explanation, arg):
  53         print explanation
  54         try:
  55             deferred = self.remote.callRemote("fooMethod", arg)
  56             deferred.addCallback(self.worked)
  57             deferred.addErrback(self.check_InsecureJelly)
  58             deferred.addErrback(self.check_MyException)
  59             deferred.addErrback(self.catch_everythingElse)
  60         except pb.DeadReferenceError:
  61             print " stale reference: the client disconnected or crashed"
  62
  63     def callOne(self):
  64         self.doCall("callOne: call with safe object", "safe string")
  65     def callTwo(self):
  66         self.doCall("callTwo: call with dangerous object", ScaryObject())
  67     def callThree(self):
  68         self.doCall("callThree: call that raises remote exception", "panic!")
  69     def callShutdown(self):
  70         print "telling them to shut down"
  71         self.remote.callRemote("shutdown")
  72     def callFour(self):
  73         self.doCall("callFour: call on stale reference", "dummy")
  74
  75     def got_obj(self, obj):
  76         self.remote = obj
  77         reactor.callLater(1, self.callOne)
  78         reactor.callLater(2, self.callTwo)
  79         reactor.callLater(3, self.callThree)
  80         reactor.callLater(4, self.callShutdown)
  81         reactor.callLater(5, self.callFour)
  82         reactor.callLater(6, reactor.stop)
  83
  84 factory = pb.PBClientFactory()
  85 reactor.connectTCP("localhost", 8800, factory)
  86 deferred = factory.getRootObject()
  87 deferred.addCallback(One().got_obj)
  88 reactor.run()