Get client role as first line

src/client.py

@@ -48,7 +48,11 @@ class Client:
 
     async def run_sending_client(self, file_path='~/output.txt'):
         self._file_path = file_path
-        _, writer = await asyncio.open_connection(host=self.host, port=self.port)
+        reader, writer = await asyncio.open_connection(host=self.host,
+                                                       port=self.port)
+        writer.write("sender\n".encode('utf-8'))
+        await writer.drain()
+        await reader.readline()  # Wait for server start signal
         await self.send(writer=writer)
 
     async def send(self, writer: asyncio.StreamWriter):
@@ -73,7 +77,11 @@ class Client:
 
     async def run_receiving_client(self, file_path='~/input.txt'):
         self._file_path = file_path
-        reader, _ = await asyncio.open_connection(host=self.host, port=self.port)
+        reader, writer = await asyncio.open_connection(host=self.host,
+                                                       port=self.port)
+        writer.write("receiver\n".encode('utf-8'))
+        await writer.drain()
+        await reader.readline()  # Wait for server start signal
         await self.receive(reader=reader)
 
     async def receive(self, reader: asyncio.StreamReader):

src/server.py

@@ -87,7 +87,10 @@ class Server:
 
         Decide whether client is sender or receiver and start transmission.
         """
-        peer_is_sender = not self.working  # TODO: ask peer role
+        client_hello = await reader.readline()
+        peer_is_sender = client_hello.decode('utf-8') == 'sender\n'
+        writer.write("Start!\n".encode('utf-8'))  # Send start signal to client
+        await writer.drain()
         self._working = True
         if peer_is_sender:
             logging.info("Sender is connecting...")