new generic secop client

new client intended as base class for all clients

- based on Ennos secop client in nicos ([WIP] provide secop client)
- self healing connection singletons
- extension for other than TCP is foreseen (by extending new uri schemes)
- extensible name mangling
- seperate rx and tx threads supporting events
- internal cache
- extensible error handling
- callback for unhandled messages
- callback for descriptive data change
- callback for node stat change (connected, disconnected)
- a short close down and reconnect without change in descriptive data
  does not disturb the client side

works with secop-gui (change follows), planned to be used for Frappy
internal secop proxy and as a replacement for secop.client.baseclient.Client
in the nicos secop device.

-> secop/client/baseclient.py to be removed after planned changes

moved secop/client/__init__.py to secop/client/console.py because secop.client
would be the natural place to put the new base class.

Change-Id: I1a7b1f1ded2221a8f9fcdd52f9cc7414e8fbe035
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/22218
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

secop/protocol/interface/tcp.py

@@ -38,10 +38,7 @@ from secop.protocol.messages import ERRORPREFIX, \
 
 DEF_PORT = 10767
 MESSAGE_READ_SIZE = 1024
-
-CR = b'\r'
-SPACE = b' '
-
+HELP = HELPREQUEST.encode()
 
 class OutputBufferOverflow(Exception):
     pass
@@ -116,9 +113,12 @@ class TCPRequestHandler(socketserver.BaseRequestHandler):
                 if origin is None:
                     break  # no more messages to process
                 origin = origin.strip()
-                if origin in (HELPREQUEST, ''):  # empty string -> send help message
+                if origin in (HELP, b''):  # empty string -> send help message
                     for idx, line in enumerate(HelpMessage.splitlines()):
-                        self.queue_async_reply((HELPREPLY, '%d' % (idx+1), line))
+                        # not sending HELPREPLY here, as there should be only one reply for every request
+                        self.queue_async_reply(('_', '%d' % (idx+1), line))
+                    # ident matches request
+                    self.queue_async_reply((HELPREPLY, None, None))
                     continue
                 try:
                     msg = decode_msg(origin)