Merge pull request #11 from andreas-amlabs/nad_telnet_filter_response

Wait for the requested response

README.md

@@ -1,7 +1,11 @@
 # nad_receiver
-Simple python API to connect to NAD receivers through the RS232 interface, and to the NAD D 7050 amplifier via tcp/ip. For the RS232 interface use the NADReceiver class, for the D 7050 use the D7050 class.
+Simple python API to connect to NAD receivers through the RS232 interface, Telnet interface or the TCP/IP interface.
+For the RS232 interface use the NADReceiver class
+For the Telnet interface use the NADReceiverTelnet class
+For the TCP/IP interface use the D7050 class
 
 Note that the RS232 interface is only tested with the NAD T748v2. Commands are implemented based on the T748v2. Those commands should work with more NAD receivers.
+The Telnet interface is only tested with the NAD T787. The Telnet interface share documentation with the RS232 interface and supports the same commands
 The supported commands can easily be extended for receivers which support more commands.
 
 For more information see the official documentation at http://nadelectronics.com/software 
@@ -26,6 +30,13 @@ D7050.select_source('Optical 1')
 D7050.mute()
 D7050.unmute()
 D7050.power_off()
+
+receiver = NADReceiverTelnet(my_nad.local)
+
+receiver.main_volume('+')  #  will increase volume with 1 and return new value
+receiver.main_volume('-')  #  will decrease volume with 1 and return new value
+receiver.main_volume('=', '-40')  # specify dB, will return new value
+print(receiver.main_volume('?'))  # will return current value
 ```
 
 supported commands with supported operators for the RS232 interface

nad_receiver/__init__.py

@@ -246,7 +246,7 @@ def mute(self):
     def unmute(self):
         """Unmute the device."""
         self._send(self.CMD_UNMUTE)
- 
+
     def select_source(self, source):
         """Select a source from the list of sources."""
         status = self.status()
@@ -267,20 +267,39 @@ class NADReceiverTelnet(NADReceiver):
 
     Known supported model: Nad T787.
     """
+    def _open_connection(self):
+        if not self.telnet:
+            try:
+                self.telnet = telnetlib.Telnet(self.host, self.port, 3)
+                # Some versions of the firmware report Main.Model=T787.
+                # some versions do not, we want to clear that line
+                self.telnet.read_until('\n'.encode(), self.timeout)
+                # Could raise eg. EOFError, UnicodeError
+            except:
+                return False
+
+        return True
+
+    def _close_connection(self):
+        """
+        Close any telnet session
+        """
+        if self.telnet:
+            self.telnet.close()
+
     def __init__(self, host, port=23, timeout=DEFAULT_TIMEOUT):
-        """Create Telnet connection."""
-        self.telnet = telnetlib.Telnet(host, port, 5)
+        """Create NADTelnet."""
+        self.telnet = None
+        self.host = host
+        self.port = port
         self.timeout = timeout
-        # Some versions of the firmware report Main.Model=T787.
-        # some versions do not, we want to clear that line
-        msg = self.telnet.read_until('\n'.encode(), self.timeout)
-        #msg.decode().strip().split('=')[1]
+        # __init__ must never raise
 
     def __del__(self):
         """
         Close any telnet session
         """
-        self.telnet.close()
+        self._close_connection()
 
     def exec_command(self, domain, function, operator, value=None):
         """
@@ -298,14 +317,33 @@ def exec_command(self, domain, function, operator, value=None):
         else:
             raise ValueError('Invalid operator provided %s' % operator)
 
-        # Not possible to test for open Telnet connection
-        # let is raise if any issues
-        # Yes, for telnet the first \r / \n is recommended only
-        self.telnet.write((''.join([cmd, '\n']).encode()))
+        if self._open_connection():
+            # For telnet the first \r / \n is recommended only
+            self.telnet.write((''.join(['\r', cmd, '\n']).encode()))
+            # Could raise eg. socket.error, UnicodeError, let the client handle it
 
-        msg = self.telnet.read_until('\n'.encode(), self.timeout)
-        msg = msg.decode().strip('\r\n')
-        #print("NAD reponded with '%s'" % msg)
+            # Test 3 x buffer is completely empty
+            # With the default timeout that means a delay at
+            # about 3+ seconds
+            loop = 3
+            while loop:
+                msg = self.telnet.read_until('\n'.encode(), self.timeout)
+                # Could raise eg. EOFError, UnicodeError, let the client handle it
 
-        return msg.strip().split('=')[1]
-        # b'Main.Volume=-12\r will return -12
+                if msg == "":
+                    # Nothing in buffer
+                    loop -= 1
+                    continue
+
+                msg = msg.decode().strip('\r\n')
+                # Could raise eg. UnicodeError, let the client handle it
+
+                #print("NAD reponded with '%s'" % msg)
+                # Wait for the response that equals the requested domain.function
+                if msg.strip().split('=')[0].lower() == '.'.join([domain, function]).lower():
+                    # b'Main.Volume=-12\r will return -12
+                    return msg.strip().split('=')[1]
+
+            raise RuntimeError('Failed to read response')
+
+        raise RuntimeError('Failed to open connection')