diff --git a/lib/network.py b/lib/network.py
index 3bf478ad..99e78641 100644
--- a/lib/network.py
+++ b/lib/network.py
@@ -40,9 +40,11 @@ import traceback
 from . import util
 from . import bitcoin
 from .bitcoin import *
+from . import constants
 from .interface import Interface
 from . import blockchain
 from .version import ELECTRUM_VERSION, PROTOCOL_VERSION
+from .i18n import _
 
 
 NODES_RETRY_INTERVAL = 60
@@ -63,7 +65,7 @@ def parse_servers(result):
             for v in item[2]:
                 if re.match("[st]\d*", v):
                     protocol, port = v[0], v[1:]
-                    if port == '': port = bitcoin.NetworkConstants.DEFAULT_PORTS[protocol]
+                    if port == '': port = constants.net.DEFAULT_PORTS[protocol]
                     out[protocol] = port
                 elif re.match("v(.?)+", v):
                     version = v[1:]
@@ -97,7 +99,7 @@ def filter_protocol(hostmap, protocol = 's'):
 
 def pick_random_server(hostmap = None, protocol = 's', exclude_set = set()):
     if hostmap is None:
-        hostmap = bitcoin.NetworkConstants.DEFAULT_SERVERS
+        hostmap = constants.net.DEFAULT_SERVERS
     eligible = list(set(filter_protocol(hostmap, protocol)) - exclude_set)
     return random.choice(eligible) if eligible else None
 
@@ -326,8 +328,10 @@ class Network(util.DaemonThread):
             await self.queue_request('blockchain.scripthash.subscribe', [h])
 
     async def request_fee_estimates(self):
+        from .simple_config import FEE_ETA_TARGETS
         self.config.requested_fee_estimates()
-        for i in bitcoin.FEE_TARGETS:
+        await self.queue_request("mempool.get_fee_histogram", [])
+        for i in FEE_ETA_TARGETS:
             await self.queue_request('blockchain.estimatefee', [i])
 
     def get_status_value(self, key):
@@ -337,6 +341,8 @@ class Network(util.DaemonThread):
             value = self.banner
         elif key == 'fee':
             value = self.config.fee_estimates
+        elif key == "fee_histogram":
+            value = self.config.mempool_fees
         elif key == 'updated':
             value = (self.get_local_height(), self.get_server_height())
         elif key == 'servers':
@@ -364,7 +370,7 @@ class Network(util.DaemonThread):
         return list(self.interfaces.keys())
 
     def get_servers(self):
-        out = bitcoin.NetworkConstants.DEFAULT_SERVERS
+        out = constants.net.DEFAULT_SERVERS
         if self.irc_servers:
             out.update(filter_version(self.irc_servers.copy()))
         else:
@@ -571,6 +577,11 @@ class Network(util.DaemonThread):
         elif method == 'server.donation_address':
             if error is None:
                 self.donation_address = result
+        elif method == "mempool.get_fee_histogram":
+            if error is None:
+                self.print_error("fee_histogram", result)
+                self.config.mempool_fees = result
+                self.notify("fee_histogram")
         elif method == 'blockchain.estimatefee':
             if error is None and result > 0:
                 i = params[0]
@@ -771,21 +782,22 @@ class Network(util.DaemonThread):
         error = response.get('error')
         result = response.get('result')
         params = response.get('params')
+        blockchain = interface.blockchain
         if result is None or params is None or error is not None:
             interface.print_error(error or 'bad response')
             return
         index = params[0]
-        connect = interface.blockchain.connect_chunk(index, result)
+        connect = blockchain.connect_chunk(index, result)
         if not connect:
             await self.connection_down(interface.server, "could not connect chunk")
             return
         # If not finished, get the next chunk
-        if interface.blockchain.height() < interface.tip:
+        if index >= len(blockchain.checkpoints) and interface.blockchain.height() < interface.tip:
             await self.request_chunk(interface, index+1)
         else:
             interface.mode = 'default'
-            interface.print_error('catch up done', interface.blockchain.height())
-            interface.blockchain.catch_up = None
+            interface.print_error('catch up done', blockchain.height())
+            blockchain.catch_up = None
         self.notify('updated')
 
     async def request_header(self, interface, height):
@@ -978,7 +990,7 @@ class Network(util.DaemonThread):
     def init_headers_file(self):
         b = self.blockchains[0]
         filename = b.path()
-        length = 80 * len(bitcoin.NetworkConstants.CHECKPOINTS) * 2016
+        length = 80 * len(constants.net.CHECKPOINTS) * 2016
         if not os.path.exists(filename) or os.path.getsize(filename) < length:
             with open(filename, 'wb') as f:
                 if length>0:
@@ -1243,7 +1255,7 @@ class Network(util.DaemonThread):
         try:
             r = q.get(True, timeout)
         except queue.Empty:
-            raise BaseException('Server did not answer')
+            raise util.TimeoutException(_('Server did not answer'))
         if r.get('error'):
             raise BaseException(r.get('error'))
         return r.get('result')
@@ -1265,7 +1277,7 @@ class Network(util.DaemonThread):
             f.write(json.dumps(cp, indent=4))
 
     def max_checkpoint(self):
-        return max(0, len(bitcoin.NetworkConstants.CHECKPOINTS) * 2016 - 1)
+        return max(0, len(constants.net.CHECKPOINTS) * 2016 - 1)
 
     async def send_async(self, messages, callback=None):
         """ if callback is None, it returns the result """
diff --git a/lib/util.py b/lib/util.py
index 9122609c..a2b4c885 100644
--- a/lib/util.py
+++ b/lib/util.py
@@ -29,6 +29,7 @@ import traceback
 import urllib
 import threading
 import hmac
+import asyncio
 
 from .i18n import _