diff --git a/iec62056_21/client.py b/iec62056_21/client.py
index 756d4ae..9220167 100644
--- a/iec62056_21/client.py
+++ b/iec62056_21/client.py
@@ -61,6 +61,12 @@ def __init__(
         self.error_parser = error_parser_class()
         self._current_baudrate: int = 300
 
+        if self.transport.TRANSPORT_REQUIRES_ADDRESS and not self.device_address:
+            raise exceptions.Iec6205621ClientError(
+                f"The transported used ({self.transport}) requires a device address "
+                f"and none was supplied."
+            )
+
     @property
     def switchover_baudrate(self):
         """
@@ -82,7 +88,7 @@ def read_single_value(self, address, additional_data="1"):
         # TODO: When not using the additional data on an EMH meter we get an ack back.
         #   a bit later we get the break message. Is the device waiting?
 
-        request = messages.CommandMessage.for_single_read(address)
+        request = messages.CommandMessage.for_single_read(address, additional_data)
         logger.info(f"Sending read request: {request}")
         self.transport.send(request.to_bytes())
 
@@ -151,7 +157,6 @@ def startup(self):
 
         # Setting the baudrate to the one propsed by the device.
         self._switchover_baudrate_char = ident_msg.switchover_baudrate_char
-        print(self.BAUDRATES_MODE_C[self._switchover_baudrate_char])
         self.identification = ident_msg.identification
         self.manufacturer_id = ident_msg.manufacturer
 
@@ -241,11 +246,7 @@ def send_init_request(self):
          you want to talk to by adding the address in the request.
 
         """
-        if self.transport.TRANSPORT_REQUIRES_ADDRESS:
-            request = messages.RequestMessage(device_address=self.device_address)
-        else:
-            request = messages.RequestMessage()
-
+        request = messages.RequestMessage(device_address=self.device_address)
         logger.info(f"Sending request message: {request}")
         self.transport.send(request.to_bytes())
         self.rest()
diff --git a/iec62056_21/exceptions.py b/iec62056_21/exceptions.py
index 858a96f..c8eee46 100644
--- a/iec62056_21/exceptions.py
+++ b/iec62056_21/exceptions.py
@@ -2,6 +2,10 @@ class Iec6205621Exception(Exception):
     """General IEC62056-21 Exception"""
 
 
+class Iec6205621ClientError(Iec6205621Exception):
+    """Client error"""
+
+
 class Iec6205621ParseError(Iec6205621Exception):
     """Error in parsing IEC62056-21 data"""
 
diff --git a/iec62056_21/transports.py b/iec62056_21/transports.py
index a2da05a..d2ecc1d 100644
--- a/iec62056_21/transports.py
+++ b/iec62056_21/transports.py
@@ -1,5 +1,6 @@
 import time
 import logging
+from typing import Tuple, Union, Optional
 
 import serial
 import socket
@@ -17,18 +18,18 @@ class BaseTransport:
     Base transport class for IEC 62056-21 communication.
     """
 
-    TRANSPORT_REQUIRES_ADDRESS = True
+    TRANSPORT_REQUIRES_ADDRESS: bool = True
 
-    def __init__(self, timeout=30):
+    def __init__(self, timeout: int = 30):
         self.timeout = timeout
 
-    def connect(self):
+    def connect(self) -> None:
         raise NotImplemented("Must be defined in subclass")
 
-    def disconnect(self):
+    def disconnect(self) -> None:
         raise NotImplemented("Must be defined in subclass")
 
-    def read(self, timeout=None):
+    def read(self, timeout: Optional[int] = None) -> bytes:
         """
         Will read a normal readout. Supports both full and partial block readout.
         When using partial blocks it will recreate the messages as it was not sent with
@@ -49,7 +50,7 @@ def read(self, timeout=None):
         while True:
 
             in_data = b""
-            duration = 0
+            duration: float = 0.0
             start_time = time.time()
             while True:
                 b = self.recv(1)
@@ -130,7 +131,12 @@ def read(self, timeout=None):
 
         return total_data
 
-    def simple_read(self, start_char, end_char, timeout=None):
+    def simple_read(
+        self,
+        start_char: Union[str, bytes],
+        end_char: Union[str, bytes],
+        timeout: Optional[int] = None,
+    ) -> bytes:
         """
         A more flexible read for use with some messages.
         """
@@ -140,7 +146,7 @@ def simple_read(self, start_char, end_char, timeout=None):
         in_data = b""
         start_char_received = False
         timeout = timeout or self.timeout
-        duration = 0
+        duration: float = 0.0
         start_time = time.time()
         while True:
             b = self.recv(1)
@@ -167,7 +173,7 @@ def simple_read(self, start_char, end_char, timeout=None):
         logger.debug(f"Received {in_data!r} over transport: {self.__class__.__name__}")
         return in_data
 
-    def send(self, data: bytes):
+    def send(self, data: bytes) -> None:
         """
         Will send data over the transport
 
@@ -176,7 +182,7 @@ def send(self, data: bytes):
         self._send(data)
         logger.debug(f"Sent {data!r} over transport: {self.__class__.__name__}")
 
-    def _send(self, data: bytes):
+    def _send(self, data: bytes) -> None:
         """
         Transport dependant sending functionality.
 
@@ -184,7 +190,7 @@ def _send(self, data: bytes):
         """
         raise NotImplemented("Must be defined in subclass")
 
-    def recv(self, chars):
+    def recv(self, chars: int) -> bytes:
         """
         Will receive data over the transport.
 
@@ -192,7 +198,7 @@ def recv(self, chars):
         """
         return self._recv(chars)
 
-    def _recv(self, chars):
+    def _recv(self, chars: int) -> bytes:
         """
         Transport dependant sending functionality.
 
@@ -200,7 +206,7 @@ def _recv(self, chars):
         """
         raise NotImplemented("Must be defined in subclass")
 
-    def switch_baudrate(self, baud):
+    def switch_baudrate(self, baud: int) -> None:
         """
         The protocol defines a baudrate switchover process. Though it might not be used
         in all available transports.
@@ -219,13 +225,13 @@ class SerialTransport(BaseTransport):
 
     TRANSPORT_REQUIRES_ADDRESS = False
 
-    def __init__(self, port, timeout=10):
+    def __init__(self, port: str, timeout: int = 10):
 
         super().__init__(timeout=timeout)
-        self.port_name = port
-        self.port = None
+        self.port_name: str = port
+        self.port: Optional[serial.Serial] = None
 
-    def connect(self, baudrate: int = 300):
+    def connect(self, baudrate: int = 300) -> None:
         """
         Creates a serial port.
         """
@@ -242,36 +248,48 @@ def connect(self, baudrate: int = 300):
             xonxoff=False,
         )
 
-    def disconnect(self):
+    def disconnect(self) -> None:
         """
         Closes and removes the serial port.
         """
+        if self.port is None:
+            raise TransportError("Serial port is closed.")
+
         self.port.close()
         self.port = None
 
-    def _send(self, data: bytes):
+    def _send(self, data: bytes) -> None:
         """
         Sends data over the serial port.
 
         :param data:
         """
+        if self.port is None:
+            raise TransportError("Serial port is closed.")
+
         self.port.write(data)
         self.port.flush()
 
-    def _recv(self, chars=1):
+    def _recv(self, chars: int = 1) -> bytes:
         """
         Receives data over the serial port.
 
         :param chars:
         """
+        if self.port is None:
+            raise TransportError("Serial port is closed.")
+
         return self.port.read(chars)
 
-    def switch_baudrate(self, baud):
+    def switch_baudrate(self, baud: int) -> None:
         """
         Creates a new serial port with the correct baudrate.
 
         :param baud:
         """
+        if self.port is None:
+            raise TransportError("Serial port is closed.")
+
         logger.info(f"Switching baudrate to: {baud}")
         self.port = self.port = serial.Serial(
             self.port_name,
@@ -300,13 +318,13 @@ class TcpTransport(BaseTransport):
     Transport class for TCP/IP communication.
     """
 
-    def __init__(self, address, timeout=30):
+    def __init__(self, address: Tuple[str, int], timeout: int = 30):
 
         super().__init__(timeout=timeout)
         self.address = address
-        self.socket = self._get_socket()
+        self.socket: Optional[socket.socket] = self._get_socket()
 
-    def connect(self):
+    def connect(self) -> None:
         """
         Connects the socket to the device network interface.
         """
@@ -316,34 +334,43 @@ def connect(self):
         logger.debug(f"Connecting to {self.address}")
         self.socket.connect(self.address)
 
-    def disconnect(self):
+    def disconnect(self) -> None:
         """
         Closes and removes the socket.
         """
+        if self.socket is None:
+            raise TransportError("Socket is closed")
+
         self.socket.close()
         self.socket = None
 
-    def _send(self, data: bytes):
+    def _send(self, data: bytes) -> None:
         """
         Sends data over the socket.
 
         :param data:
         """
+        if self.socket is None:
+            raise TransportError("Socket is closed")
+
         self.socket.sendall(data)
 
-    def _recv(self, chars=1):
+    def _recv(self, chars: int = 1) -> bytes:
         """
         Receives data from the socket.
 
         :param chars:
         """
+        if self.socket is None:
+            raise TransportError("Socket is closed")
+
         try:
             b = self.socket.recv(chars)
         except (OSError, IOError, socket.timeout, socket.error) as e:
             raise TransportError from e
         return b
 
-    def switch_baudrate(self, baud):
+    def switch_baudrate(self, baud: int) -> None:
         """
         Baudrate has not meaning in TCP/IP so we just dont do anything.
 
@@ -351,7 +378,7 @@ def switch_baudrate(self, baud):
         """
         pass
 
-    def _get_socket(self):
+    def _get_socket(self) -> socket.socket:
         """
         Create a correct socket.
         """
diff --git a/tests/test_client.py b/tests/test_client.py
new file mode 100644
index 0000000..c69c8fc
--- /dev/null
+++ b/tests/test_client.py
@@ -0,0 +1,22 @@
+import pytest
+from iec62056_21 import exceptions, client, transports
+
+
+class TestIec6205621Client:
+    def test_with_no_address_when_required_raises_client_error(self):
+        with pytest.raises(exceptions.Iec6205621ClientError):
+            c = client.Iec6205621Client.with_tcp_transport(("192.168.1.1", 5000))
+
+    def test_can_create_client_with_tcp_transport(self):
+        c = client.Iec6205621Client.with_tcp_transport(
+            "192.168.1.1", device_address="00000000"
+        )
+
+    def test_no_address_when_required_raises_client_error(self):
+        trans = transports.TcpTransport(address=("192.168.1.1", 5000))
+        with pytest.raises(exceptions.Iec6205621ClientError):
+            c = client.Iec6205621Client(transport=trans)
+
+    def test_can_create_client_tcp_transport(self):
+        trans = transports.TcpTransport(address=("192.168.1.1", 5000))
+        c = client.Iec6205621Client(transport=trans, device_address="00000000")