(issue #7) Do some clean up when server sockets close

Clients connecting to pyDriveWire over a socket can terminate suddenly.  If
the clients opened Virtual Serial channels those can remain open and may
cause problems when the client reconnects.  The fix adds a callback
mechanism to DWServerSocket and DWSimpleSocket when the connection closes.
The callback is set to the Server's cmdInit method.  This resets all the
open disk files and closes all of the Virtual Serial channels.

dwsocket.py

@@ -48,15 +48,15 @@ def _read(self, count=256):
             (ri, _, _) = select.select([self.conn.fileno()], [], [], 1)
         except Exception as e:
             print(str(e))
-            raise Exception("Connection closed")
+            raise Exception("%s: _read (1): Connection closed" % self)
             self._close()
         if any(ri):
             # print "dwsocket: reading"
             data = self.conn.recv(count)
         # else:
             # print "dwsocket: waiting"
         if data == '':
-            raise Exception("Connection closed")
+            raise Exception("%s: _read (2): Connection closed" % self)
             self._close()
         # if data:
         # 	print "r",data
@@ -73,7 +73,7 @@ def _write(self, data):
             (_, wi, _) = select.select([], [self.conn.fileno()], [], 1)
         except Exception as e:
             print(str(e))
-            raise ("Connection closed")
+            raise Exception("%s: _write: Connection closed" % self)
             self._close()
             n = -1
         if any(wi):
@@ -155,10 +155,11 @@ def _cleanup(self):
 
 
 class DWSocketServer(DWSocket):
-    def __init__(self, host='localhost', port=6809, debug=False):
+    def __init__(self, host='localhost', port=6809, debug=False, closedCb=None):
         DWSocket.__init__(self, host=host, port=port, debug=debug)
         self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
         self.sock.bind(('0.0.0.0', self.port))
+        self.closedCb = closedCb
 
     def accept(self):
         while not self.abort:
@@ -186,6 +187,9 @@ def _read(self, count=256):
             print(str(e))
             self.conn.close()
             self.conn = None
+            if self.closedCb:
+                print("%s: Calling callback: %s" % (self, self.closedCb))
+                self.closedCb(self)
         return data
 
 
@@ -249,7 +253,8 @@ def __init__(
             port=6809,
             conn=None,
             reconnect=False,
-            debug=False):
+            debug=False,
+            closedCb=None):
         self.host = host
         self.port = int(port)
         self.conn = conn
@@ -262,6 +267,7 @@ def __init__(
             self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
         self.reconnect = reconnect
         self.debug = debug
+        self.closedCb = closedCb
 
     def name(self):
         return "%s %s:%s" % (self.__class__, self.host, self.port)
@@ -295,6 +301,9 @@ def read(self, n=1, timeout=None):
             while not self.abort and d == '' and self.reconnect:
                 print("socket: %s: Disconnected" % (self))
                 self.close()
+                if self.closedCb:
+                    print("%s: Calling callback: %s" % (self, self.closedCb))
+                    self.closedCb(self)
                 print(
                     "socket: %s: Reconnecting to %s:%s" %
                     (self, self.host, self.port))

pyDriveWire.py

@@ -20,6 +20,8 @@
 import platform
 import tempfile
 
+from dwconstants import *
+
 VERSION = 'v0.5c'
 
 defaultConfigValues = {
@@ -388,6 +390,8 @@ def CreateServer(args, instance, instances, lock):
     for cmd in cmds:
         print parser.parse(cmd)
 
+    if isinstance(conn, DWSocket) or isinstance(conn, DWSimpleSocket):
+        conn.closedCb = lambda x: dws.cmdInit(OP_INIT)
     return dws