PyGi: tcpclientsrc : not linked

#!/usr/bin/env python

import os, platform

try:
  import gi
except:
  print("No GI")
try:
  gi.require_version('Gtk', '3.0')
  from gi.repository import GObject,Gtk as Gtk
except:
  print("No Gtk")
try:
  gi.require_version ('Gst', '1.0')
  from gi.repository import Gst
except:
  print("No Gst")
try:
# Needed for window.get_xid(), xvimagesink.set_window_handle(), respectively:
  gi.require_version('GdkX11', '3.0')
  from gi.repository import GdkX11
except:
  print("No GdkX11 3.0")
try:
  gi.require_version('GstVideo', '1.0')
  from gi.repository import GstVideo
except:
  print("No GstVideo 1.0")
  sys.exit(1)


class GTK_Main(object):

    def __init__(self):
        ## Create a window,
        self.gladefile = ("hello_Gstream_tcpclient_work.glade")
        self.builder = Gtk.Builder()
        self.builder.add_from_file(self.gladefile)
        self.builder.connect_signals(self)

        ## Create objects by name from Glade
        self.window = self.builder.get_object("window")
        self.movie_window = self.builder.get_object("movie_window")
        self.button1 = self.builder.get_object("button1")
        self.button2 = self.builder.get_object("button2")
        self.button3 = self.builder.get_object("button3")
        self.entry_host_1 = self.builder.get_object("entry_host_1")
        self.entry_host_2 = self.builder.get_object("entry_host_2")
        self.entry_host_3 = self.builder.get_object("entry_host_3")
        self.entry_port_1 = self.builder.get_object("entry_port_1")
        self.entry_port_2 = self.builder.get_object("entry_port_2")
        self.entry_port_3 = self.builder.get_object("entry_port_3")
        self.window.show_all()

        ## Create pibeline & connect bus
        self.player = Gst.Pipeline.new("player")
        bus = self.player.get_bus()
        bus.add_signal_watch()
        bus.enable_sync_message_emission()
        bus.connect("message", self.on_message)
        bus.connect("sync-message::element", self.on_sync_message)

        ## Create tcpclientsr, gdpdepay, rtph264depay, h264parse, decodebin,
        ## videoconvert, autovideosink
        self.tcpclientsrc_1 = Gst.ElementFactory.make("tcpclientsrc", "tcpclientsrc_1")
        self.gdpdepay_1 = Gst.ElementFactory.make("gdpdepay", "gdpdepay_1")
        self.rtph264depay_1 = Gst.ElementFactory.make("rtph264depay", "rtph264depay_1")
        self.h264parse_1 = Gst.ElementFactory.make("h264parse", "h264parse_1")
        self.decodebin_1 = Gst.ElementFactory.make("decodebin", "decodebin_1")
        self.videoconvert_1 = Gst.ElementFactory.make("videoconvert", "videoconvert_1")
        self.autovideosink = Gst.ElementFactory.make("autovideosink", "autovideosink")

        ## Add elements to pibeline
        self.player.add(self.tcpclientsrc_1)
        self.player.add(self.gdpdepay_1)
        self.player.add(self.rtph264depay_1)
        self.player.add(self.h264parse_1)
        self.player.add(self.decodebin_1)
        self.player.add(self.videoconvert_1)
        self.player.add(self.autovideosink)

        ## Link elements
        self.tcpclientsrc_1.link(self.gdpdepay_1)
        self.gdpdepay_1.link(self.rtph264depay_1)
        self.rtph264depay_1.link(self.h264parse_1)
        self.h264parse_1.link(self.decodebin_1)
        self.decodebin_1.link(self.videoconvert_1)
        self.videoconvert_1.link(self.autovideosink)

    ## Create handles
    def on_window_destroy(self, object, data=None):
        Gtk.main_quit()

    def on_button1_clicked(self, object, data=None):
        w = self.entry_host_1.get_text().strip()
        self.start_stop(w)

	## Play - Stop
    def start_stop(self, w):
        if self.button1.get_label() == "Start":
            tcpiphost_1 = self.entry_host_1.get_text().strip()
            tcpport_1 = int(self.entry_port_1.get_text().strip())
            #print tcpiphost_1
            #print tcpport_1
            self.tcpclientsrc_1.set_property("host", tcpiphost_1)
            self.tcpclientsrc_1.set_property("port", tcpport_1)
            self.button1.set_label("Stop")
            self.player.set_state(Gst.State.PLAYING)
        else:
            self.player.set_state(Gst.State.NULL)
            self.button1.set_label("Start")

	## Message system
    def on_message(self, bus, message):
        t = message.type
        if t == Gst.MessageType.EOS:
            self.player.set_state(Gst.State.NULL)
            self.button1.set_label("Start")
        elif t == Gst.MessageType.ERROR:
            self.player.set_state(Gst.State.NULL)
            err, debug = message.parse_error()
            print "Error: %s" % err, debug
            self.button1.set_label("Start")

    def on_sync_message(self, bus, message):
        if message.get_structure().get_name() == 'prepare-window-handle':
            imagesink = message.src
            imagesink.set_property("force-aspect-ratio", True)
            imagesink.set_window_handle(self.movie_window.get_property('window').get_xid())


GObject.threads_init()
Gst.init(None)
GTK_Main()
Gtk.main()