CoAP server (FTD) to client (SED) communication failure.

[Jis]

Hi,

I am currently working on a two way communication between an nrf52840 thread host and an nrf52840 thread client over coap. I have nrf connect sdk version 2.9.0 in both host and client. Sending data from the coap client to the server is working properly. But sending an acknowledgement packet from the host back to the client after receiving a data packet from the client, seems to be not working. Though the coap_send_request function runs successfully, when I sniffed for packets using wireshark, I do not see any ACK packets being sent out from the host and is also missing in the client's host packet handler function. Please find attached the wireshark capture file (1c00 is my host rloc16 and 1c01 is my client rloc16). The code snippet I use to send the ACK packets are shown below. Please let me know if you need more details.

Thanks,
Jis

#define COAP_CMD_SEND_HOST_DATA 53
#define COAP_ACK_ID 85
const struct sockaddr *coap_client_addr = <Client IPv6 address>;
const char *const hostinfo_option[] = { "host-info", NULL };

uint8_t ack_payload[] = {COAP_CMD_SEND_HOST_DATA, COAP_ACK_ID, 0};

if (coap_send_request(COAP_METHOD_PUT, coap_client_addr, hostinfo_option, ack_payload, sizeof(ack_payload), on_client_ack_reply) < 0)
{
    LOG_ERR("Sending ACK failed");
}
else
{
    LOG_INFO("Sending ACK success");
}

static int on_client_ack_reply(const struct coap_packet *response, struct coap_reply *reply, const struct sockaddr *from)
{
    LOG_INF("Received reply after sending ACK");
    return 0;
}

Host2waycomms.pcapng

[dejans]

Hi,

I will look into this tomorrow or at the beginning of next week. I expect to get back to you by the middle of next week.

Best regards,
Dejan

[Jis]

Thanks. Also I would like to share an update on my tests. Although by using the coap_send_request API, the host never sent out the packet, but if I create a new CoAP message using otCoapNewMessage and transmit it using otCoapSendResponse API call, the host is sending the packet and the client is receiving it correctly. I would like to know whether the coap_send_request API should not be used for my purpose or is there any step I am missing. Thank you.

[dejans]

Hi,

Can you share your network key to decrypt your pcap?

It is recommended that you use (if possible) OpenThread CoAP implementation rather than the Zephyr one. Here are some API examples
github.com/.../cli_coap.cpp
This could minimize the size of the application in the future.

Best regards,
Dejan

[Jis]

Hi dejans,

Thanks for getting back. Please use the key - 01b784d43453af0ca6a1fa19f3cf3131 - for decrypting the pcap file.

Cheers,
Jis

[dejans]

Hi Jis,

We are looking into this issue. I expect to get back to you during next week.

Best regards,
Dejan

[dejans]

Hi Jis,

CoAP messages are interpreted in Wireshark as malformed. Would it be possible for you to start start using OT CoAP API which is well integrated into Thread stack?

Best regards,
Dejan