mqtt_simple counting received hexvalues above 0x7F double

[lowielameire]

USED SDK: v1.4.99-dev1

USED BOARD: nRF9160DK

Received hexvalues above 0x7F (decimal = 127) are counted double in p->message.payload.len

Any ideas what might be te problem?

void mqtt_evt_handler(struct mqtt_client *const c,
		      const struct mqtt_evt *evt)
{
	int err;

	switch (evt->type) {
	case MQTT_EVT_CONNACK:
		if (evt->result != 0) {
			LOG_ERR("MQTT connect failed: %d", evt->result);
			break;
		}

		LOG_INF("MQTT client connected");
		subscribe();
		break;

	case MQTT_EVT_DISCONNECT:
		LOG_INF("MQTT client disconnected: %d", evt->result);
		break;

	case MQTT_EVT_PUBLISH: {
		const struct mqtt_publish_param *p = &evt->param.publish;

		LOG_INF("MQTT PUBLISH result=%d len=%d",
			evt->result, p->message.payload.len);
		err = publish_get_payload(c, p->message.payload.len);

Kind regards,
Lowie

[Håkon Alseth]

Hi Lowie,

 

Received hexvalues above 0x7F (decimal = 127) are counted double in p->message.payload.len

Do you mean that any value over "127" decimal will show as 2 bytes? Or will they be represented as a "double"?

 

The protocol itself is agnostic to the data format that is send and received; it takes in byte aligned input and sends it. If you receive a different length than expected; it is likely because the sender packs it in a different format than you expect.

 

Kind regards,

Håkon

[lowielameire]

I meant that any value over 127 decimal will show as 2 bytes. I tested a "MQTT box" mqtt client and a "Node.js" mqtt client. The result is the same.

[Håkon Alseth]

A signed char has the range of -128 to 127; if you go outside of this scope, it'll be expanded to a signed short (2 byte).

 

Kind regards,

Håkon

[lowielameire]

Could mqtt_simple be using UTF-8 encoding?
When sending 0xFF and 0xA1 the received payload is 0xC3 0xBF 0xC2 0xA1

[lowielameire]

Problem solved. You were right, it was due to the mqtt clients and their encoding. Thanks for the help!