First version of a API for the receiverLiveViewer

APIs/receiverLiveViewerAPI.py

+# API to communicate with receiverLiveViewer
+
+import zmq
+import socket
+
+
+class ReceiverQuery():
+
+    context      = None
+
+    signalIp     = None
+    signalPort   = None
+    dataIp       = None
+    hostname     = None
+    dataPort     = None
+
+    signalSocket = None
+    dataSocket   = None
+
+    context = None
+
+
+    def __init__(self, signalPort, signalIp, dataPort, dataIp = "0.0.0.0"):
+
+        # ZMQ applications always start by creating a context,
+        # and then using that for creating sockets
+        # (source: ZeroMQ, Messaging for Many Applications by Pieter Hintjens)
+        self.context = zmq.Context()
+
+        self.signalIp   = signalIp
+        self.signalPort = signalPort
+        self.dataIp     = dataIp
+        self.hostname   = socket.gethostname()
+        self.dataPort   = dataPort
+
+
+        # To send a notification that a Displayer is up and running, a communication socket is needed
+        self.signalSocket = self.context.socket(zmq.REQ)
+        connectionStr = "tcp://" + str(self.signalIp) + ":" + str(self.signalPort)
+        print connectionStr
+        self.signalSocket.connect(connectionStr)
+        print  "signalSocket is connected to ", connectionStr
+
+
+        # An additional socket is needed to establish the data retriving mechanism
+        self.dataSocket = self.context.socket(zmq.REQ)
+        connectionStr = "tcp://" + str(self.dataIp) + ":" + str(self.dataPort)
+        self.dataSocket.bind(connectionStr)
+        print  "dataSocket is bound to ", connectionStr
+
+
+        # Send the signal that the communication infrastructure should be established
+        print "Sending Start Signal to receiver"
+        sendMessage = "START_DISPLAYER," + str(self.hostname) + "," + str(self.dataPort)
+        try:
+            self.signalSocket.send (sendMessage)
+            #  Get the reply.
+            message = self.signalSocket.recv()
+            print "Recieved signal: ", message
+        except Exception as e:
+            print "Could not communicate with receiver"
+            print "Error was: ", e
+
+
+    ##
+    #
+    # Queries the receiver for new files
+    #
+    # returns the path of the newest file
+    #
+    ##
+    def communicateWithReceiver(self):
+
+        sendMessage = "NEXT_FILE"
+        print "Asking for next file with message", sendMessage
+        try:
+            self.dataSocket.send (sendMessage)
+        except Exception as e:
+            print "Could not communicate with receiver"
+            print "Error was: ", e
+            return ""
+
+        try:
+            #  Get the reply.
+            message = self.dataSocket.recv()
+        except Exception as e:
+            message = ""
+            print "Could not communicate with receiver"
+            print "Error was: ", e
+
+        return message
+
+
+    ##
+    #
+    # Send signal that the displayer is quitting, close ZMQ connections, destoying context
+    #
+    ##
+    def stopZmq(self):
+
+        print "Sending Start Signal to receiver"
+        sendMessage = "STOP_DISPLAYER," + str(self.hostname) + "," + str(self.dataPort)
+        try:
+            self.signalSocket.send (sendMessage)
+            #  Get the reply.
+            message = self.signalSocket.recv()
+            print "Recieved signal: ", message
+        except Exception as e:
+            print "Could not communicate with receiver"
+            print "Error was: ", e
+
+        try:
+            print "closing ZMQ sockets..."
+            if self.signalSocket:
+                self.signalSocket.close(linger=0)
+            if self.dataSocket:
+                self.dataSocket.close(linger=0)
+            print "closing ZMQ Sockets...done."
+        except Exception as e:
+            print "closing ZMQ Sockets...failed."
+            print e
+
+        try:
+            print"closing zmqContext..."
+            if self.context:
+                self.context.destroy()
+                self.context = None
+            "closing zmqContext...done."
+        except Exception as e:
+            print "closing zmqContext...failed."
+            print e
+
+
+    def __exit__(self):
+        self.stopZmq()
+
+
+    def __del__(self):
+        self.stopZmq()
+
+