Simplify transport_serial (modbus use)

pymodbus/transport/transport_serial.py

@@ -12,29 +12,27 @@
 class SerialTransport(asyncio.Transport):
     """An asyncio serial transport."""
 
+    force_poll: bool = False
+
     def __init__(self, loop, protocol, *args, **kwargs):
         """Initialize."""
         super().__init__()
         self.async_loop = loop
         self._protocol: asyncio.BaseProtocol = protocol
         self.sync_serial = serial.serial_for_url(*args, **kwargs)
         self._write_buffer = []
-        self._has_reader = False
-        self._has_writer = False
+        self.poll_task = None
         self._poll_wait_time = 0.0005
         self.sync_serial.timeout = 0
         self.sync_serial.write_timeout = 0
 
     def setup(self):
         """Prepare to read/write"""
-        self.async_loop.call_soon(self._protocol.connection_made, self)
-        if os.name == "nt":
-            self._has_reader = self.async_loop.call_later(
-                self._poll_wait_time, self._poll_read
-            )
+        if os.name == "nt" or self.force_poll:
+            self.poll_task = asyncio.create_task(self._polling_task())
         else:
             self.async_loop.add_reader(self.sync_serial.fileno(), self._read_ready)
-            self._has_reader = True
+        self.async_loop.call_soon(self._protocol.connection_made, self)
 
     def close(self, exc=None):
         """Close the transport gracefully."""
@@ -43,13 +41,13 @@ def close(self, exc=None):
         with contextlib.suppress(Exception):
             self.sync_serial.flush()
 
-        if self._has_reader:
-            if os.name == "nt":
-                self._has_reader.cancel()
-            else:
-                self.async_loop.remove_reader(self.sync_serial.fileno())
-            self._has_reader = False
         self.flush()
+        if self.poll_task:
+            self.poll_task.cancel()
+            _ = asyncio.ensure_future(self.poll_task)
+            self.poll_task = None
+        else:
+            self.async_loop.remove_reader(self.sync_serial.fileno())
         self.sync_serial.close()
         self.sync_serial = None
         with contextlib.suppress(Exception):
@@ -58,21 +56,13 @@ def close(self, exc=None):
     def write(self, data):
         """Write some data to the transport."""
         self._write_buffer.append(data)
-        if not self._has_writer:
-            if os.name == "nt":
-                self._has_writer = self.async_loop.call_soon(self._poll_write)
-            else:
-                self.async_loop.add_writer(self.sync_serial.fileno(), self._write_ready)
-                self._has_writer = True
+        if not self.poll_task:
+            self.async_loop.add_writer(self.sync_serial.fileno(), self._write_ready)
 
     def flush(self):
         """Clear output buffer and stops any more data being written"""
-        if self._has_writer:
-            if os.name == "nt":
-                self._has_writer.cancel()
-            else:
-                self.async_loop.remove_writer(self.sync_serial.fileno())
-            self._has_writer = False
+        if not self.poll_task:
+            self.async_loop.remove_writer(self.sync_serial.fileno())
         self._write_buffer.clear()
 
     # ------------------------------------------------
@@ -141,34 +131,32 @@ def _write_ready(self):
         """Asynchronously write buffered data."""
         data = b"".join(self._write_buffer)
         try:
-            if nlen := self.sync_serial.write(data) < len(data):
-                self._write_buffer = data[nlen:]
-                return True
+            if (nlen := self.sync_serial.write(data)) < len(data):
+                self._write_buffer = [data[nlen:]]
+                if not self.poll_task:
+                    self.async_loop.add_writer(
+                        self.sync_serial.fileno(), self._write_ready
+                    )
+                return
             self.flush()
         except (BlockingIOError, InterruptedError):
-            return True
+            return
         except serial.SerialException as exc:
             self.close(exc=exc)
-        return False
 
-    def _poll_read(self):
-        if self._has_reader:
-            try:
-                self._has_reader = self.async_loop.call_later(
-                    self._poll_wait_time, self._poll_read
-                )
+    async def _polling_task(self):
+        """Poll and try to read/write."""
+        try:
+            while True:
+                await asyncio.sleep(self._poll_wait_time)
+                while self._write_buffer:
+                    self._write_ready()
                 if self.sync_serial.in_waiting:
                     self._read_ready()
-            except serial.SerialException as exc:
-                self.close(exc=exc)
-
-    def _poll_write(self):
-        if not self._has_writer:
-            return
-        if self._write_ready():
-            self._has_writer = self.async_loop.call_later(
-                self._poll_wait_time, self._poll_write
-            )
+        except serial.SerialException as exc:
+            self.close(exc=exc)
+        except asyncio.CancelledError:
+            pass
 
 
 async def create_serial_connection(loop, protocol_factory, *args, **kwargs):

test/sub_transport/test_basic.py

@@ -325,6 +325,10 @@ async def test_external_methods(self):
         comm.close()
         comm = SerialTransport(mock.MagicMock(), mock.Mock(), "dummy")
         comm.abort()
-        assert await create_serial_connection(
+        transport, protocol = await create_serial_connection(
             asyncio.get_running_loop(), mock.Mock, url="dummy"
         )
+        await asyncio.sleep(0.1)
+        assert transport
+        assert protocol
+        transport.close()

test/sub_transport/test_comm.py

@@ -9,6 +9,7 @@
     CommType,
     ModbusProtocol,
 )
+from pymodbus.transport.transport_serial import SerialTransport
 
 
 FACTOR = 1.2 if not pytest.IS_WINDOWS else 4.2
@@ -125,6 +126,61 @@ async def test_connected(self, client, server, use_comm_type):
             assert not server.active_connections
         server.transport_close()
 
+    def wrapped_write(self, data):
+        """Wrap serial write, to split parameters."""
+        return self.serial_write(data[:2])
+
+    @pytest.mark.parametrize(
+        ("use_comm_type", "use_host"),
+        [
+            (CommType.SERIAL, "socket://localhost:5020"),
+        ],
+    )
+    async def test_split_serial_packet(self, client, server):
+        """Test connection and data exchange."""
+        assert await server.transport_listen()
+        assert await client.transport_connect()
+        await asyncio.sleep(0.5)
+        assert len(server.active_connections) == 1
+        server_connected = list(server.active_connections.values())[0]
+        test_data = b"abcd"
+
+        self.serial_write = (  # pylint: disable=attribute-defined-outside-init
+            client.transport.sync_serial.write
+        )
+        with mock.patch.object(
+            client.transport.sync_serial, "write", wraps=self.wrapped_write
+        ):
+            client.transport_send(test_data)
+            await asyncio.sleep(0.5)
+        assert server_connected.recv_buffer == test_data
+        assert not client.recv_buffer
+        client.transport_close()
+        server.transport_close()
+
+    @pytest.mark.parametrize(
+        ("use_comm_type", "use_host"),
+        [
+            (CommType.SERIAL, "socket://localhost:5020"),
+        ],
+    )
+    async def test_serial_poll(self, client, server):
+        """Test connection and data exchange."""
+        assert await server.transport_listen()
+        SerialTransport.force_poll = True
+        assert await client.transport_connect()
+        await asyncio.sleep(0.5)
+        SerialTransport.force_poll = False
+        assert len(server.active_connections) == 1
+        server_connected = list(server.active_connections.values())[0]
+        test_data = b"abcd" * 1000
+        client.transport_send(test_data)
+        await asyncio.sleep(0.5)
+        assert server_connected.recv_buffer == test_data
+        assert not client.recv_buffer
+        client.transport_close()
+        server.transport_close()
+
     @pytest.mark.parametrize(
         ("use_comm_type", "use_host"),
         [