--- a/client/client.py	Fri Mar 01 16:32:42 2019 +0100
+++ b/client/client.py	Fri Mar 01 16:33:03 2019 +0100
@@ -1,9 +1,11 @@
 #!/usr/bin/env python3
 
 import arguments
+import json
 import os
 import os.path as path
 import sys
+import urllib.parse as url
 import zmq
 
 import PyQt5.QtWidgets as wid
@@ -157,6 +159,13 @@
             value += stock.current_num * stock.current_price
         return value
 
+    def serialize(self):
+        s = {'cash': self.cash, 'stock': {}, '_stockdepot': True}
+        for sym, stock in self.stock.items():
+            stock_sum = {'num': stock.current_num}
+            s['stock'][sym] = stock_sum
+        return json.dumps(s)
+
 # A stock position in a depot.
 class DepotStock:
     sym = ''
@@ -211,7 +220,6 @@
             self.max = value
 
         previous, nxt = (self.current - 1) % self.MAX_LEN, (self.current + 1) % self.MAX_LEN
-        # Shift graph to the left
         self.series.replace(self.current, self.current, value)
         self.series.replace(nxt, nxt, 0)
 
@@ -315,16 +323,17 @@
 
     on_new_message = core.pyqtSignal(dict)
 
-    def __init__(self, creds):
+    def __init__(self, zctx, creds):
         """callback is a function taking received data dicts."""
         super().__init__()
 
-        self.zctx = zmq.Context()
+        self.zctx = zctx
         self.sock = self.zctx.socket(zmq.SUB)
         self.sock.setsockopt(zmq.IPV6, 1)
         self.sock.subscribe('')
+        self.sock.setsockopt(zmq.RCVTIMEO, 0)
+
         self.sock.connect('tcp://{}'.format(creds.addr))
-        self.sock.setsockopt(zmq.RCVTIMEO, 0)
         fd = self.sock.getsockopt(zmq.FD)
         self.socknot = core.QSocketNotifier(fd, core.QSocketNotifier.Read)
         self.socknot.activated.connect(self.on_activated)
@@ -337,9 +346,70 @@
                 if '_stockdata' not in msg:
                     return
                 self.on_new_message.emit(msg)
-        except Exception:
+        except Exception as e:
             return
 
+# Manages communication back to the server, like depot settings etc.
+class CallbackSocket(core.QObject):
+    creds = None
+    socket = None
+    waiting = False
+    queue = []
+
+    def __init__(self, zctx, creds):
+        super().__init__()
+        self.creds = creds
+        socket = zctx.socket(zmq.REQ)
+        socket.setsockopt(zmq.IPV6, 1)
+        socket.setsockopt(zmq.RCVTIMEO, 0)
+        socket.setsockopt(zmq.SNDTIMEO, 10)
+        
+        u = url.urlparse(creds.addr)
+        hostport = u.netloc or u.path
+        (host, _, port) = hostport.partition(':')
+        socket.connect('tcp://{}:{}'.format(host, int(port if port else '9988') + 1))
+        self.socket = socket
+
+        fd = self.socket.getsockopt(zmq.FD)
+        self.socknot = core.QSocketNotifier(fd, core.QSocketNotifier.Read)
+        self.socknot.activated.connect(self.on_reply)
+
+    def login(self):
+        self.try_send({'_stocklogin': True})
+
+    def send_depot(self, depot):
+        summary = depot.serialize()
+        self.try_send(summary)
+
+    def wrap(self, msg):
+        return json.dumps({'_stockcallback': True, 'user': self.creds.user, 'password': self.creds.password, 'msg': msg})
+
+    def try_send(self, msg):
+        msg = self.wrap(msg)
+        if self.waiting:
+            self.queue.append(msg)
+        else:
+            try:
+                self.socket.send_string(msg)
+                self.waiting = True
+            except Exception as e:
+                print ('DEBUG: Send failed on REQ socket: ', e)
+                self.queue.append(msg)
+        assert len(self.queue) < 5
+
+    @core.pyqtSlot(int)
+    def on_reply(self, _sock):
+        try:
+            msg = self.socket.recv_json()
+            print('DEBUG: Received response: {}'.format(msg))
+            self.waiting = False
+
+            # Try sending oldest message.
+            if len(self.queue) > 0:
+                self.try_send(self.queue.pop(0))
+        except Exception as e:
+            print ('DEBUG: RECV failed on REQ socket: ', e)
+
 
 class Client(arguments.BaseArguments, wid.QWidget):
     _doc = """
@@ -353,6 +423,9 @@
     creds = Creds()
     depot = Depot()
     depot_widget = None
+    zctx = zmq.Context()
+    timer = None
+    callback_sock = None
 
     def __init__(self):
         super(wid.QWidget, self).__init__()
@@ -366,17 +439,25 @@
         ccd.accepted.connect(self.start_wait_window)
         ccd.show_dialog()
 
+        self.timer = core.QTimer(self)
+        self.timer.setInterval(1500)
+        self.timer.timeout.connect(self.on_periodic_timer)
+        self.timer.start()
+
     def set_creds(self, creds):
         self.creds = creds
 
     def start_wait_window(self):
-        self.sock = ClientSocket(self.creds)
-        self.sock.on_new_message.connect(self.on_new_data)
-
-        self.start_main_window()
+        self.mainvbox = wid.QVBoxLayout(self)
         self.waiting = wid.QLabel("Waiting for incoming stock data - hang tight!", self)
         self.mainvbox.addWidget(self.depot_widget)
         self.mainvbox.addWidget(self.waiting)
+        self.show()
+        
+        self.sock = ClientSocket(self.zctx, self.creds)
+        self.sock.on_new_message.connect(self.on_new_data)
+        self.callback_sock = CallbackSocket(self.zctx, self.creds)
+        self.callback_sock.login()
 
     stock_widgets = {}
 
@@ -394,6 +475,13 @@
                 self.depot.add_stock(sym, depotstock)
                 self.depot.priceUpdated.connect(sw.update)
 
+    @core.pyqtSlot()
+    def on_periodic_timer(self):
+        print('DEBUG: timer expired!')
+        if not self.callback_sock:
+            return
+        self.callback_sock.send_depot(self.depot)
+    
     mainvbox = None
     hboxes = []
     widgets_per_hbox = 2
@@ -408,10 +496,6 @@
             self.hboxes[-1].addWidget(sw)
         return
 
-    def start_main_window(self):
-        self.mainvbox = wid.QVBoxLayout(self)
-        self.show()
-
 
 def main():
     app = wid.QApplication(sys.argv)