Add OgQMP recv method

recv method is useful for receiving information that was not previously
requested (such as "events"). This patch also implements automatic handshake
on OgQMP by sending an "qmp_capabilities" request.

src/virtual/ogOperations.py

@@ -50,6 +50,10 @@ class OgQMP:
                 if err.errno == errno.ECONNREFUSED:
                     raise Exception('cannot connect to qemu')
 
+        out = self.talk(str({"execute": "qmp_capabilities"}))
+        if 'QMP' not in out:
+            raise Exception('cannot handshake qemu')
+
     def talk(self, data):
         try:
             self.sock.send(bytes(data, 'utf-8'))
@@ -61,6 +65,21 @@ class OgQMP:
         if self.sock in readable:
             try:
                 out = self.sock.recv(4096).decode('utf-8')
+                out = json.loads(out)
+            except socket.error as err:
+                raise Exception('cannot talk to qemu')
+        else:
+            raise Exception('timeout when talking to qemu')
+        return out
+
+    def recv(self, timeout=QMP_TIMEOUT):
+        readset = [self.sock]
+        readable, _, _ = select.select(readset, [], [], timeout)
+
+        if self.sock in readable:
+            try:
+                out = self.sock.recv(4096).decode('utf-8')
+                out = json.loads(out)
             except socket.error as err:
                 raise Exception('cannot talk to qemu')
         else:
@@ -68,7 +87,10 @@ class OgQMP:
         return out
 
     def disconnect(self):
-        self.sock.close()
+        try:
+            self.sock.close()
+        except:
+            pass
 
 class OgVirtualOperations:
     def __init__(self):