make ip/port voice packet logic more clear

Adds comments and also rewrites the logic in a way that is much easier
to see what is going on. For example you can now easily see that the
port is actually encoded in little endian (which is different from
everything else).

discord/voice_client.py

@@ -211,16 +211,16 @@ class VoiceClient:
         self.socket.sendto(packet, (self.endpoint_ip, self.voice_port))
         recv = yield from self.loop.sock_recv(self.socket, 70)
         log.debug('received packet in initial_connection: {}'.format(recv))
-        ip = []
 
-        for x in range(4, len(recv)):
-            val = recv[x]
-            if val == 0:
-                break
-            ip.append(chr(val))
+        # the ip is ascii starting at the 4th byte and ending at the first null
+        ip_start = 4
+        ip_end = recv.index(0, ip_start)
+        self.ip = recv[ip_start:ip_end].decode('ascii')
+
+        # the port is a little endian unsigned short in the last two bytes
+        # yes, this is different endianness from everything else
+        self.port = struct.unpack_from('<H', recv, len(recv) - 2)[0]
 
-        self.ip = ''.join(ip)
-        self.port = recv[len(recv) - 2] | recv[len(recv) - 1] << 8
         log.debug('detected ip: {} port: {}'.format(self.ip, self.port))
 
         payload = {