twisted python self.transport is not working just after connecting to server

Question

I have been working on a P2P chat application based on kivy and twisted frameworks, I was hoping to get a lay of the land but I have run into this problem where if a client needs to connect to another client (via its server) it needs to perform a kind of handshake,

now the initial step was to connect to the client ;

conn = reactor.connectTCP(host, port, CommCoreClientFactory(self))

and then write into the connection;

conn.transport.write("data..\r\n")

Here the connection succeeds but the line doesn't go through, I have condensed the above code as per my intent, please see the method add_peer_to_swarm(self, pid, host) in comm/twisscomm.py

my clientProtocol/Factory and serverProtocol/Factory code can be found below; (they can be found in comm/commcoreclient.py and comm/commcoreserver.py resp.)

Client Protocol

class CommCoreClientProtocol(LineReceiver):

"""
Communications core client protocol code.
"""

def __init__(self, factory):

    self._peer_host = None
    self._peer_port = None
    self._peer_repr = None
    self.factory    = factory

def connectionMade(self):
    "Run when connection is established with server."

    self._peer_host = self.transport.getPeer().host
    self._peer_port = self.transport.getPeer().port
    self._peer_repr = self._peer_host + " on " + str(self._peer_port)

    Logger.debug(
        "Connection success! Connected to {}".format(self._peer_repr))

def connectionLost(self, reason):
    "Run when connection is lost with server."

    Logger.warn("Lost connection with peer {}".format(self._peer_repr))

def lineReceived(self, line):
    "Run when response is recieved from server."

    response = self.factory.app.handle_response(line)

    if response:
        print response

    Logger.debug("Recieved : {}".format(base64.b64encode(line)))

Client Factory

class CommCoreClientFactory(protocol.ReconnectingClientFactory):

protocol = CommCoreClientProtocol

def __init__(self, app):

    self.app = app

def startedConnecting(self, connector):
    "Run when initiaition of connection takes place."

    Logger.debug("Attempting connection...")

def buildProtocol(self, addr):
    "Build protocol on successful connection."

    Logger.debug("Connected.")
    Logger.debug("Resetting reconnection delay.")

    # Reset the delay on connection success
    self.resetDelay()

    # Overridden build protocol
    #client_protocol = self.protocol()
    #client_protocol.factory = self
    #return client_protocol

    return CommCoreClientProtocol(self)

def clientConnectionLost(self, connector, reason):
    "Run when connection with server is lost."

    #self.app.print_message("connection lost")
    Logger.debug("Lost connection: {}".format(reason.getErrorMessage()))

    return protocol.ReconnectingClientFactory.clientConnectionLost(
        self, connector, reason
    )

def clientConnectionFailed(self, connector, reason):
    "Run when attempt to connect with server fails."

    #self.app.print_message("connection failed")
    Logger.debug("Connection failed. {}".format(reason.getErrorMessage()))

    return protocol.ReconnectingClientFactory.clientConnectionFailed(
        self, connector, reason
    )

Server Protocol

class CommCoreServerProtocol(LineReceiver):

"Server backend to pocess the commands"

def __init__(self):

    self._peer_host = None
    self._peer_port = None
    self._peer_repr = None

def connectionMade(self):
    "Run when connection is established with server."

    self._peer_host = self.transport.getPeer().host
    self._peer_port = self.transport.getPeer().port
    self._peer_repr = self._peer_host + " on " + str(self._peer_port)

    Logger.debug(
        "Connection success! Connected to {}".format(self._peer_repr))

def connectionLost(self, reason):
    "Run when connection is lost with server."

    Logger.error("Lost connection with peer {}".format(self._peer_repr))

def lineReceived(self, line):

    print "REVCD LINE!", line

    response = self.factory.app.handle_recieved_data(line)

    if response:
        #self.transport.write(response)
        self.sendLine(response)

Server Factory

class CommCoreServerFactory(protocol.Factory):

protocol = CommCoreServerProtocol

def __init__(self, app):

    self.app = app

(Pardon the shoddy indent!)

I would like to know where I may be going wrong. Also If you are interested I have filed this issue. If you go through my code (comm/twiscomm.py) you will see some things may not work completely on the server side especially with the handle_received_data() but this is never even called as the data is not received.

Answer 1

The client howto explains and demonstrates how to use Twisted's network client APIs.

The API documentation for reactor.connectTCP also tells you things about its return value - an IConnector - notably, an interface lacking any transport attribute.