add ping / pong to keep the websockets running

owrx/websocket.py

@@ -9,6 +9,12 @@ import logging
 
 logger = logging.getLogger(__name__)
 
+OPCODE_TEXT_MESSAGE = 0x01
+OPCODE_BINARY_MESSAGE = 0x02
+OPCODE_CLOSE = 0x08
+OPCODE_PING = 0x09
+OPCODE_PONG = 0x0A
+
 
 class IncompleteRead(Exception):
     pass
@@ -55,6 +61,8 @@ class WebSocketConnection(object):
                 ws_key_toreturn.decode()
             ).encode()
         )
+        self.pingTimer = None
+        self.resetPing()
 
     def get_header(self, size, opcode):
         ws_first_byte = 0b10000000 | (opcode & 0x0F)
@@ -90,13 +98,17 @@ class WebSocketConnection(object):
 
         # string-type messages are sent as text frames
         if type(data) == str:
-            header = self.get_header(len(data), 1)
+            header = self.get_header(len(data), OPCODE_TEXT_MESSAGE)
             data_to_send = header + data.encode("utf-8")
         # anything else as binary
         else:
-            header = self.get_header(len(data), 2)
+            header = self.get_header(len(data), OPCODE_BINARY_MESSAGE)
             data_to_send = header + data
 
+        self._sendBytes(data_to_send)
+
+    def _sendBytes(self, data_to_send):
+
         def chunks(l, n):
             """Yield successive n-sized chunks from l."""
             for i in range(0, len(l), n):
@@ -122,44 +134,50 @@ class WebSocketConnection(object):
             logger.exception("ValueError while writing data")
             self.close()
 
-    def protected_read(self, num):
-        data = self.handler.rfile.read(num)
-        if data is None:
-            raise Drained()
-        if len(data) != num:
-            raise IncompleteRead()
-        return data
-
     def interrupt(self):
         self.interruptPipeSend.send(bytes(0x00))
 
     def read_loop(self):
+        def protected_read(num):
+            data = self.handler.rfile.read(num)
+            if data is None:
+                raise Drained()
+            if len(data) != num:
+                raise IncompleteRead()
+            return data
+
         WebSocketConnection.connections.append(self)
         self.open = True
         while self.open:
             (read, _, _) = select.select([self.interruptPipeRecv, self.handler.rfile], [], [])
             if self.handler.rfile in read:
                 available = True
+                self.resetPing()
                 while self.open and available:
                     try:
-                        header = self.protected_read(2)
+                        header = protected_read(2)
                         opcode = header[0] & 0x0F
                         length = header[1] & 0x7F
                         mask = (header[1] & 0x80) >> 7
                         if length == 126:
-                            header = self.protected_read(2)
+                            header = protected_read(2)
                             length = (header[0] << 8) + header[1]
                         if mask:
-                            masking_key = self.protected_read(4)
-                        data = self.protected_read(length)
+                            masking_key = protected_read(4)
+                        data = protected_read(length)
                         if mask:
                             data = bytes([b ^ masking_key[index % 4] for (index, b) in enumerate(data)])
-                        if opcode == 1:
+                        if opcode == OPCODE_TEXT_MESSAGE:
                             message = data.decode("utf-8")
                             self.messageHandler.handleTextMessage(self, message)
-                        elif opcode == 2:
+                        elif opcode == OPCODE_BINARY_MESSAGE:
                             self.messageHandler.handleBinaryMessage(self, data)
-                        elif opcode == 8:
+                        elif opcode == OPCODE_PING:
+                            self.sendPong()
+                        elif opcode == OPCODE_PONG:
+                            # since every read resets the ping timer, there's nothing to do here.
+                            pass
+                        elif opcode == OPCODE_CLOSE:
                             logger.debug("websocket close frame received; closing connection")
                             self.open = False
                         else:
@@ -176,17 +194,12 @@ class WebSocketConnection(object):
         logger.debug("websocket loop ended; shutting down")
 
         self.messageHandler.handleClose()
+        self.cancelPing()
 
         logger.debug("websocket loop ended; sending close frame")
 
-        try:
-            header = self.get_header(0, 8)
-            self.handler.wfile.write(header)
-            self.handler.wfile.flush()
-        except ValueError:
-            logger.exception("ValueError while writing close frame:")
-        except OSError:
-            logger.exception("OSError while writing close frame:")
+        header = self.get_header(0, OPCODE_CLOSE)
+        self._sendBytes(header)
 
         try:
             WebSocketConnection.connections.remove(self)
@@ -197,6 +210,24 @@ class WebSocketConnection(object):
         self.open = False
         self.interrupt()
 
+    def cancelPing(self):
+        if self.pingTimer:
+            self.pingTimer.cancel()
+
+    def resetPing(self):
+        self.cancelPing()
+        self.pingTimer = threading.Timer(30, self.sendPing)
+        self.pingTimer.start()
+
+    def sendPing(self):
+        header = self.get_header(0, OPCODE_PING)
+        self._sendBytes(header)
+        self.resetPing()
+
+    def sendPong(self):
+        header = self.get_header(0, OPCODE_PONG)
+        self._sendBytes(header)
+
 
 class WebSocketException(Exception):
     pass