Toit

I am attempting to connect to the rsmb  MQTT-SN broker.  In my client, I have setup code:
```
  constructor --.gateway --.port=1885:

  open -> none:
    network = net.open
    udp_socket = network.udp_open
    server_address = net.SocketAddress (net.IpAddress.parse gateway) port
    udp_socket.connect server_address
```
and where I send the payload
```
  send_ payload/ByteArray -> none:
    msg := udp.Datagram payload server_address
    udp_socket.send msg
    packet_id++
```
On the server log, I see  `CWNAN0075W Socket error 107 (Transport endpoint is not connected) in getpeername for socket 4`
This is reported, running the client on either host or device.
Is there any obvious error you see in the snippets above?

Thx. Found a simple C test case (for QOS -1) in Eclipse Paho, rsmb broker responds correctly to that.  The `udp_socket.connect` is unnecessary.  Same behavior when removed.  Will use Wireshark, expect then I formatted the packet incorrectly.

Fixed.  Badly formatted flag field in the MQTT-SN packet, but strange rsmbroker reported  `Socket error 107`