Telematica: minor bug fixes.

telematica/ass1/async.py

@@ -80,7 +80,7 @@ class ClientConnection(object, AsyncBase, asyncore.dispatcher):
                     tb.tb_frame.f_code.co_filename,
                     tb.tb_frame.f_code.co_name,
                     str(tb.tb_lineno)
-                    ))
+                ))
                 tb = tb.tb_next
 
             file, function, line = tbinfo[-1]
@@ -110,9 +110,8 @@ class ClientConnection(object, AsyncBase, asyncore.dispatcher):
             try:
                 chunk = self.recv(1)
             except socket.error, e:
-                # Suppress "Resource temporarily unavailable" exceptions.
+                # Handle "Resource temporarily unavailable" exceptions.
                 if e.errno == EAGAIN:
-                    # Wait 5 ms
                     import time
                     time.sleep(0.005)
                     continue
@@ -207,7 +206,7 @@ class ClientConnection(object, AsyncBase, asyncore.dispatcher):
         Helper function used to parse the server notifications. This way,
         message parsing is separated from the notification logic.
         """
-        match = re.match('^SAY ([^\r\n:/]+)/(.+)', buf)
+        match = re.match('^SAY ([^\x00-\x1F:/]+)/([^\x00-\x1F]+)', buf)
         if match:
             if 'message' in self.event_list:
                 self.event_list['message'](self, match.group(1), match.group(2))

telematica/ass1/doc/implementation.rst

@@ -32,7 +32,8 @@ Since some functionality of the chat connection is used in both the client and
 server, it is wise to create a base class containing those methods: *AsyncBase*.
 We used the *asyncore.dispatcher* class (part of the python standard library) to
 create a nice abstraction layer on top of the socket. The abstraction layer is
-event-oriented and provides various event callback functions:
+event-oriented and provides the following event callback functions (among some
+other less relevant ones):
 
  1. **handle_write**.
 
@@ -76,6 +77,12 @@ connection does take messages from the queue, if its local message buffer is
 empty (which means all its data is sent to the server or the connection is
 just initialised).
 
+The protocol uses the Backus-Naur form and therefore, we chose regular
+expressions to validate incoming messages from the server. Regexes are easier to
+maintain than handwritten parsers, since they allow you to check for certain
+ranges of characters (for example, the control character range is
+**[\\x00-\\x1F]**).
+
 Text-based interface (using curses)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -191,5 +198,11 @@ We implemented the following commands:
 Server side
 ----------
 
-Foo
+Multiple client handling
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+The class *Server* accepts the incoming connections from clients and initialises
+a request handler (see class *RequestHandler*) for each accepted connection. The
+servers logs all its information, warnings and errors to stdout. To change the
+behaviour of the server log, alter the configuration file *logging.conf*.
 

telematica/ass1/server.py

@@ -32,6 +32,9 @@ class Server(asyncore.dispatcher):
         self.port = port
         self.handler = handler
 
+        # Dictonary which maps ip/port tuple to client data object.
+        self.clients = {}
+
         logging.config.fileConfig('logging.conf')
         self.log = logging.getLogger('Server')
 
@@ -42,9 +45,6 @@ class Server(asyncore.dispatcher):
         self.log.info('waiting for incoming connections on port %s.' % port)
         self.listen(5)
 
-        # Dictonary which maps ip/port tuple to client data object.
-        self.clients = {}
-
     def handle_accept(self):
         """
         Handle the incoming connection's request.
@@ -149,12 +149,27 @@ class RequestHandler(AsyncBase, asyncore.dispatcher):
         self.parse_response(buf)
 
     def handle_error(self):
+        import sys
+        t, v, tb = sys.exc_info()
+        tbinfo = []
+        while tb:
+            tbinfo.append((
+                tb.tb_frame.f_code.co_filename,
+                tb.tb_frame.f_code.co_name,
+                str(tb.tb_lineno)
+            ))
+            tb = tb.tb_next
+        file, function, line = tbinfo[-1]
+
+        self.log.error('%s raised "%s" in %s:%s' \
+                % (str(v), function, file, line))
+        self.log.error(' '.join(['[%s|%s|%s]' % x for x in tbinfo]))
         self.server.disconnect_client(self.address)
 
     def parse_response(self, buf):
         """
         >>> class DummyServer(object):
-        ...     def __init__(self): self.log = None
+        ...     def __init__(self): self.log = None; self.clients = {}
         ...     def change_username(self, addr, username): pass
         ...     def send_all(self, msg, sender): pass
         >>> req = RequestHandler(None, None, None, DummyServer())
@@ -171,14 +186,20 @@ class RequestHandler(AsyncBase, asyncore.dispatcher):
             # Client wants to chat.
             return self.send_positive('Ok')
         if cmd == 'USER':
-            # User changes/sets its username.
-            if re.match(ur'^[^\u0000-\u001f\u007f-\u009f/:]+$', buf[5:]):
+            # User changes/sets its username. Make sure the username is not
+            # already taken. If the name is valid, notify the other clients.
+            name = buf[5:]
+            for c in self.server.clients:
+                if self.server.clients[c].username == name \
+                        and self.server.clients[c].handler != self:
+                    return self.send_negative('Username already taken.')
+            if re.match(ur'^[^\u0000-\u001f\u007f-\u009f/:]+$', name):
                 if not self.username:
-                    self.send_all('JOIN %s' % buf[5:], True)
+                    self.send_all('JOIN %s' % name, True)
                 else:
                     self.send_all('RENAME %s/%s' \
-                            % (self.username, buf[5:]), True)
-                self.set_username(buf[5:])
+                            % (self.username, name), True)
+                self.set_username(name)
                 return self.send_positive('Ok')
             return self.send_negative('Invalid username.')