Fix close bug in userver demo.

Author: peterhinch

v3/as_drivers/client_server/heartbeat.py

@@ -14,6 +14,11 @@ async def heartbeat(tms):
     elif platform == 'esp8266':
         from machine import Pin
         led = Pin(2, Pin.OUT, value=1)
+    elif platform == 'esp32':
+        # Some boards have an LED
+        #from machine import Pin
+        #led = Pin(2, Pin.OUT, value=1)
+        return  # Reference board has no LED
     elif platform == 'linux':
         return  # No LED
     else:

v3/as_drivers/client_server/userver.py

@@ -45,17 +45,17 @@ async def run_client(self, sreader, swriter):
         await sreader.wait_closed()
         print('Client {} socket closed.'.format(self.cid))
 
-    def close(self):
+    async def close(self):
         print('Closing server')
         self.server.close()
         await self.server.wait_closed()
-        print('Server closed')
+        print('Server closed.')
 
 server = Server()
 try:
     asyncio.run(server.run())
 except KeyboardInterrupt:
     print('Interrupted')  # This mechanism doesn't work on Unix build.
 finally:
-    server.close()
+    asyncio.run(server.close())
     _ = asyncio.new_event_loop()