MQTT publisher sample for both tls and non-tls using SIMCOM7080 modem

[DineshDK03]

What I am trying to do
I am doing MQTT publisher sample using SIMCOM7080 modem connected to esp32-wrover devkit.

1. For sample without TLS , getting ERROR Transport read error: -11
2. For sample with TLS , getting ERROR mqtt_connect: -9

To Reproduce
Steps to reproduce the behavior: Clone the sample folders from here
west build -p -b esp32 && west flash && west espressif monitor

Expected behavior
Expecting mqtt publish response OK without any errors.

Logs and console output

1. Output for MQTT publisher sample without TLS

[00:00:07.711,000] <inf> modem_simcom_sim7080: Manufacturer: SIMCOM_Ltd
[00:00:07.798,000] <inf> modem_simcom_sim7080: Model: SIMCOM_SIM7080
[00:00:07.944,000] <inf> modem_simcom_sim7080: Revision: 1951B04SIM7080
[00:00:08.031,000] <inf> modem_simcom_sim7080: IMEI: 860016040123775
[00:00:08.450,000] <inf> modem_simcom_sim7080: CPIN: 1
[00:00:11.508,000] <inf> modem_simcom_sim7080: RSSI: -72
[00:00:13.566,000] <inf> modem_simcom_sim7080: CGATT: 1
[00:00:14.566,000] <inf> modem_simcom_sim7080: Waiting for network
[00:00:14.627,000] <inf> modem_simcom_sim7080: CREG: 5
*** Booting Zephyr OS build v2.7.99-4492-g4cd0cd56c8b3  ***
[00:00:15.764,000] <inf> modem_simcom_sim7080: PDP context: 1
[00:00:15.764,000] <inf> modem_simcom_sim7080: Network active.
[00:00:15.764,000] <dbg> net_core: net_init: (0x3ffd73a0): Priority 90
[00:00:15.764,000] <dbg> net_pkt: net_pkt_init: (0x3ffd73a0): Allocating 4 RX (256 bytes), 4 TX (256 bytes), 0 RX data (0 bytes) and 0 TX data (0 bytes) buffers
[00:00:15.764,000] <dbg> net_core: l3_init: (0x3ffd73a0): Network L3 init done
[00:00:15.764,000] <dbg> net_if: net_if_init: (0x3ffd73a0): 
[00:00:15.764,000] <dbg> net_tc: net_tc_tx_init: (0x3ffd73a0): No TX thread created
[00:00:15.764,000] <dbg> net_if: init_iface: (0x3ffd73a0): On iface 0x3ffb0d0c
[00:00:15.764,000] <dbg> net_tc: net_tc_rx_init: (0x3ffd73a0): [0] Starting RX handler 0x3ffd5970 stack size 1504 prio 15 coop(-1)
[00:00:15.764,000] <dbg> net_if: net_if_post_init: (0x3ffd73a0): 
[00:00:15.764,000] <dbg> net_if: net_if_up: (0x3ffd73a0): iface 0x3ffb0d0c
[00:00:16.164,000] <inf> net_mqtt_publisher_sample: DNS resolved for broker.hivemq.com:1883
[00:00:16.164,000] <inf> net_mqtt_publisher_sample: get_mqtt_broker_addrinfo: 0 <OK>
[00:00:16.164,000] <inf> net_mqtt_publisher_sample: attempting to connect: 
[00:00:16.164,000] <dbg> net_mqtt_sock_tcp: mqtt_client_tcp_connect: (0x3ffd73a0): Created socket 0
[00:00:16.381,000] <inf> modem_simcom_sim7080: +CAOPEN: 0
[00:00:16.381,000] <dbg> net_mqtt_sock_tcp: mqtt_client_tcp_connect: (0x3ffd73a0): Connect completed
[00:00:16.381,000] <dbg> net_mqtt_enc: connect_request_encode: Encoding Protocol Description.
4d 51 54 54                                      |MQTT             
[00:00:16.381,000] <dbg> net_mqtt_enc: pack_utf8_str: (0x3ffd73a0): >> str_size:00000006 cur:0x3ffd78f2, end:0x3ffd796d
[00:00:16.381,000] <dbg> net_mqtt_enc: pack_uint16: (0x3ffd73a0): >> val:0004 cur:0x3ffd78f2, end:0x3ffd796d
[00:00:16.381,000] <dbg> net_mqtt_enc: connect_request_encode: (0x3ffd73a0): Encoding Protocol Version 04.
[00:00:16.381,000] <dbg> net_mqtt_enc: pack_uint8: (0x3ffd73a0): >> val:04 cur:0x3ffd78f8, end:0x3ffd796d
[00:00:16.381,000] <dbg> net_mqtt_enc: pack_uint8: (0x3ffd73a0): >> val:00 cur:0x3ffd78f9, end:0x3ffd796d
[00:00:16.381,000] <dbg> net_mqtt_enc: connect_request_encode: (0x3ffd73a0): Encoding Keep Alive Time 003c.
[00:00:16.381,000] <dbg> net_mqtt_enc: pack_uint16: (0x3ffd73a0): >> val:003c cur:0x3ffd78fa, end:0x3ffd796d
[00:00:16.381,000] <dbg> net_mqtt_enc: connect_request_encode: Encoding Client Id.
7a 65 70 68 79 72 5f 70  75 62 6c 69 73 68 65 72 |zephyr_p ublisher
[00:00:16.381,000] <dbg> net_mqtt_enc: pack_utf8_str: (0x3ffd73a0): >> str_size:00000012 cur:0x3ffd78fc, end:0x3ffd796d
[00:00:16.381,000] <dbg> net_mqtt_enc: pack_uint16: (0x3ffd73a0): >> val:0010 cur:0x3ffd78fc, end:0x3ffd796d
[00:00:16.381,000] <dbg> net_mqtt_enc: mqtt_encode_fixed_header: (0x3ffd73a0): << msg type:0x10 length:0x0000001c
[00:00:16.381,000] <dbg> net_mqtt_enc: packet_length_encode: (0x3ffd73a0): >> length:0x0000001c cur:(nil), end:(nil)
[00:00:16.381,000] <dbg> net_mqtt_enc: mqtt_encode_fixed_header: (0x3ffd73a0): Fixed header length = 02
[00:00:16.381,000] <dbg> net_mqtt_enc: pack_uint8: (0x3ffd73a0): >> val:10 cur:0x3ffd78f0, end:0x3ffd796d
[00:00:16.381,000] <dbg> net_mqtt_enc: packet_length_encode: (0x3ffd73a0): >> length:0x0000001c cur:0x3ffd78f1, end:0x3ffd796d
[00:00:16.698,000] <dbg> net_mqtt: client_connect: (0x3ffd73a0): Connect completed
[00:00:16.777,000] <inf> modem_simcom_sim7080: Data available on socket: 0
[00:00:16.777,000] <dbg> net_mqtt: mqtt_input: (0x3ffd73a0): state:0x00000002
[00:00:16.820,000] <dbg> net_mqtt_dec: unpack_uint8: (0x3ffd73a0): >> cur:0x3ffd796d, end:0x3ffd796f
[00:00:16.820,000] <dbg> net_mqtt_dec: unpack_uint8: (0x3ffd73a0): << val:20
[00:00:16.820,000] <dbg> net_mqtt_dec: packet_length_decode: (0x3ffd73a0): length:0x00000002
[00:00:16.820,000] <dbg> net_mqtt_rx: mqtt_read_message_chunk: (0x3ffd73a0): [CID 0x3ffd7484]: Transport read error: -11
[00:00:16.820,000] <dbg> net_mqtt_sock_tcp: mqtt_client_tcp_disconnect: (0x3ffd73a0): Closing socket 0
[00:00:16.820,000] <dbg> net_sock: z_impl_zsock_close: (0x3ffd73a0): close: ctx=0x3ffd6ebc, fd=0
[00:00:16.873,000] <inf> net_mqtt_publisher_sample: MQTT client disconnected -113
[00:00:16.873,000] <dbg> net_mqtt_sock_tcp: mqtt_client_tcp_connect: (0x3ffd73a0): Created socket 0
[00:00:17.035,000] <inf> modem_simcom_sim7080: +CAOPEN: 0
[00:00:17.035,000] <dbg> net_mqtt_sock_tcp: mqtt_client_tcp_connect: (0x3ffd73a0): Connect completed
[00:00:17.035,000] <dbg> net_mqtt_enc: connect_request_encode: Encoding Protocol Description.
4d 51 54 54                                      |MQTT             
[00:00:17.035,000] <dbg> net_mqtt_enc: pack_utf8_str: (0x3ffd73a0): >> str_size:00000006 cur:0x3ffd78f2, end:0x3ffd796d
[00:00:17.035,000] <dbg> net_mqtt_enc: pack_uint16: (0x3ffd73a0): >> val:0004 cur:0x3ffd78f2, end:0x3ffd796d
[00:00:17.035,000] <dbg> net_mqtt_enc: connect_request_encode: (0x3ffd73a0): Encoding Protocol Version 04.
[00:00:17.035,000] <dbg> net_mqtt_enc: pack_uint8: (0x3ffd73a0): >> val:04 cur:0x3ffd78f8, end:0x3ffd796d
[00:00:17.035,000] <dbg> net_mqtt_enc: pack_uint8: (0x3ffd73a0): >> val:00 cur:0x3ffd78f9, end:0x3ffd796d
[00:00:17.035,000] <dbg> net_mqtt_enc: connect_request_encode: (0x3ffd73a0): Encoding Keep Alive Time 003c.
[00:00:17.035,000] <dbg> net_mqtt_enc: pack_uint16: (0x3ffd73a0): >> val:003c cur:0x3ffd78fa, end:0x3ffd796d
[00:00:17.035,000] <dbg> net_mqtt_enc: connect_request_encode: Encoding Client Id.
7a 65 70 68 79 72 5f 70  75 62 6c 69 73 68 65 72 |zephyr_p ublisher
[00:00:17.035,000] <dbg> net_mqtt_enc: pack_utf8_str: (0x3ffd73a0): >> str_size:00000012 cur:0x3ffd78fc, end:0x3ffd796d
[00:00:17.035,000] <dbg> net_mqtt_enc: pack_uint16: (0x3ffd73a0): >> val:0010 cur:0x3ffd78fc, end:0x3ffd796d
[00:00:17.035,000] <dbg> net_mqtt_enc: mqtt_encode_fixed_header: (0x3ffd73a0): << msg type:0x10 length:0x0000001c
[00:00:17.035,000] <dbg> net_mqtt_enc: packet_length_encode: (0x3ffd73a0): >> length:0x0000001c cur:(nil), end:(nil)
[00:00:17.035,000] <dbg> net_mqtt_enc: mqtt_encode_fixed_header: (0x3ffd73a0): Fixed header length = 02
[00:00:17.035,000] <dbg> net_mqtt_enc: pack_uint8: (0x3ffd73a0): >> val:10 cur:0x3ffd78f0, end:0x3ffd796d
[00:00:17.035,000] <dbg> net_mqtt_enc: packet_length_encode: (0x3ffd73a0): >> length:0x0000001c cur:0x3ffd78f1, end:0x3ffd796d
[00:00:17.352,000] <inf> modem_simcom_sim7080: Data available on socket: 0
[00:00:17.352,000] <dbg> net_mqtt: client_connect: (0x3ffd73a0): Connect completed
[00:00:17.352,000] <dbg> net_mqtt: mqtt_input: (0x3ffd73a0): state:0x00000002
[00:00:17.420,000] <dbg> net_mqtt_dec: unpack_uint8: (0x3ffd73a0): >> cur:0x3ffd796d, end:0x3ffd796f
[00:00:17.420,000] <dbg> net_mqtt_dec: unpack_uint8: (0x3ffd73a0): << val:20
[00:00:17.420,000] <dbg> net_mqtt_dec: packet_length_decode: (0x3ffd73a0): length:0x00000002
[00:00:17.420,000] <dbg> net_mqtt_rx: mqtt_read_message_chunk: (0x3ffd73a0): [CID 0x3ffd7484]: Transport read error: -11
[00:00:17.420,000] <dbg> net_mqtt_sock_tcp: mqtt_client_tcp_disconnect: (0x3ffd73a0): Closing socket 0
[00:00:17.420,000] <dbg> net_sock: z_impl_zsock_close: (0x3ffd73a0): close: ctx=0x3ffd6ebc, fd=0
[00:00:17.472,000] <inf> net_mqtt_publisher_sample: MQTT client disconnected -113

2. Output for MQTT publisher sample with TLS

*** Booting Zephyr OS build v2.7.99-4492-g4cd0cd56c8b3  ***
[00:00:15.684,000] <dbg> modem_cmd_handler: cmd_handler_process_rx_buf: match cmd [OK] (len:2)
[00:00:15.736,000] <dbg> modem_cmd_handler: cmd_handler_process_rx_buf: match cmd [OK] (len:2)
[00:00:15.765,000] <dbg> modem_cmd_handler: cmd_handler_process_rx_buf: match cmd [+APP PDP: ] (len:18)
[00:00:15.765,000] <inf> modem_simcom_sim7080: PDP context: 1
[00:00:15.765,000] <inf> modem_simcom_sim7080: Network active.
[00:00:15.765,000] <dbg> modem_simcom_sim7080: change_state: Changing state to (1)
[00:00:15.875,000] <dbg> modem_cmd_handler: cmd_handler_process_rx_buf: match cmd [OK] (len:2)
[00:00:16.303,000] <dbg> modem_cmd_handler: cmd_handler_process_rx_buf: match cmd [+CDNSGIP: ] (len:80)
[00:00:16.303,000] <inf> mqtt_publisher_sample: DNS resolved for awvvdv9pe6z46-ats.iot.ap-southeast-1.amazonaws.com:8883
[00:00:16.303,000] <inf> mqtt_publisher_sample: get_mqtt_broker_addrinfo: 0 <OK>
[00:00:16.303,000] <inf> mqtt_publisher_sample: tls_init: 0 <OK>
[00:00:16.303,000] <inf> mqtt_publisher_sample: attempting to connect:
[00:00:16.303,000] <dbg> net_sock: z_impl_zsock_close: (0x3ffc9420): close: ctx=0x3ffc8f3c, fd=0
[00:00:16.303,000] <inf> mqtt_publisher_sample: mqtt_connect: -9 <ERROR>
[00:00:16.803,000] <dbg> net_sock: z_impl_zsock_close: (0x3ffc9420): close: ctx=0x3ffc8fc0, fd=0
[00:00:16.803,000] <inf> mqtt_publisher_sample: mqtt_connect: -9 <ERROR>
[00:00:17.304,000] <dbg> net_sock: z_impl_zsock_close: (0x3ffc9420): close: ctx=0x3ffc9044, fd=0
[00:00:17.304,000] <inf> mqtt_publisher_sample: mqtt_connect: -9 <ERROR>
[00:00:17.804,000] <inf> mqtt_publisher_sample: try_to_connect: -22 <ERROR>

Environment (please complete the following information):

• OS: Manjaro Linux
• Toolchain zephyr-sdk-0.13.2
• Latest

[rlubos]

Try calling wait()/mqtt_input() in a loop (https://github.com/DineshDK03/zephyr-mqtt-sim7080/blob/main/mqtt_publisher_modem/src/main.c#L221) until connected flag is set or an error occurs. If this does not help then it's likely an issue with the offloaded socket implementation, I can't help here, I don't know this modem nor have means to reproduce.

As for TLS, that offloaded implementation does not to support TLS on their side.

[ghost]

Hi @rlubos
I also met a similar issue. I am doing an MQTT publisher sample: https://docs.zephyrproject.org/latest/samples/net/mqtt_publisher/README.html using NRF5340DK connected to Module sim: SIM7090G-EVB Kit.
This is log console:

uart:~$
[00:00:06.851,043] <inf> modem_simcom_sim7080: Manufacturer: SIMCOM_Ltd
[00:00:06.904,785] <inf> modem_simcom_sim7080: Model: SIMCOM_SIM7090
[00:00:06.959,808] <inf> modem_simcom_sim7080: Revision: 1951B03SIM7090
[00:00:07.013,763] <inf> modem_simcom_sim7080: IMEI: 863213040071917
[00:00:07.227,355] <inf> modem_simcom_sim7080: CPIN: 1
[00:00:10.280,639] <inf> modem_simcom_sim7080: RSSI: -78
[00:00:12.283,935] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:13.287,261] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:14.290,527] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:15.293,853] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:16.297,119] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:17.300,415] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:18.303,710] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:19.306,976] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:20.310,211] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:21.313,568] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:22.316,833] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:23.320,129] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:24.323,516] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:25.326,812] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:26.330,078] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:27.333,374] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:28.336,639] <inf> modem_simcom_sim7080: CGATT: 0
[00:00:29.339,965] <inf> modem_simcom_sim7080: CGATT: 1
[00:00:30.340,515] <inf> modem_simcom_sim7080: Waiting for network
[00:00:30.343,414] <inf> modem_simcom_sim7080: CREG: 1
[00:00:31.368,316] <inf> modem_simcom_sim7080: PDP context: 1
[00:00:31.368,377] <inf> modem_simcom_sim7080: Network active.
*** Booting Zephyr OS build v3.3.99-ncs1-1 ***
[00:00:31.368,896] <inf> net_config: Initializing network
[00:00:31.368,957] <inf> net_config: IPv4 address: 192.0.2.1
[00:00:31.369,018] <inf> net_mqtt_publisher_sample: attempting to connect:
[00:00:31.970,458] <inf> modem_simcom_sim7080: +CAOPEN: 0
[00:00:31.980,346] <inf> net_mqtt: Connect completed
[00:00:33.215,301] <inf> modem_simcom_sim7080: Data available on socket: 0
[00:00:33.219,665] <inf> net_mqtt_sock_tcp: Closing socket 0
[00:00:33.225,494] <inf> net_mqtt_publisher_sample: MQTT client disconnected -113
[00:00:33.794,097] <inf> modem_simcom_sim7080: +CAOPEN: 0
[00:00:33.804,992] <inf> net_mqtt: Connect completed
[00:00:34.567,016] <inf> modem_simcom_sim7080: Data available on socket: 0
[00:00:34.571,350] <inf> net_mqtt_sock_tcp: Closing socket 0
[00:00:34.577,178] <inf> net_mqtt_publisher_sample: MQTT client disconnected -113
[00:00:35.350,982] <inf> modem_simcom_sim7080: +CAOPEN: 0
[00:00:35.360,839] <inf> net_mqtt: Connect completed
[00:00:36.001,495] <inf> modem_simcom_sim7080: Data available on socket: 0
[00:00:36.005,889] <inf> net_mqtt_sock_tcp: Closing socket 0
[00:00:36.012,268] <inf> net_mqtt_publisher_sample: MQTT client disconnected -113
[00:00:36.631,408] <inf> modem_simcom_sim7080: +CAOPEN: 0
[00:00:36.641,387] <inf> net_mqtt: Connect completed
[00:00:37.162,322] <inf> modem_simcom_sim7080: Data available on socket: 0
[00:00:37.166,656] <inf> net_mqtt_sock_tcp: Closing socket 0
[00:00:37.172,668] <inf> net_mqtt_publisher_sample: MQTT client disconnected -113
[00:00:37.667,297] <inf> modem_simcom_sim7080: +CAOPEN: 0
[00:00:37.677,185] <inf> net_mqtt: Connect completed
[00:00:38.241,302] <inf> modem_simcom_sim7080: Data available on socket: 0
[00:00:38.245,635] <inf> net_mqtt_sock_tcp: Closing socket 0
[00:00:38.251,647] <inf> net_mqtt_publisher_sample: MQTT client disconnected -113
[00:00:38.755,371] <inf> modem_simcom_sim7080: +CAOPEN: 0
[00:00:38.765,869] <inf> net_mqtt: Connect completed
[00:00:39.297,363] <inf> modem_simcom_sim7080: Data available on socket: 0
[00:00:39.301,696] <inf> net_mqtt_sock_tcp: Closing socket 0
[00:00:39.307,403] <inf> net_mqtt_publisher_sample: MQTT client disconnected -113
[00:00:39.814,025] <inf> modem_simcom_sim7080: +CAOPEN: 0
[00:00:39.824,432] <inf> net_mqtt: Connect completed
[00:00:40.355,529] <inf> modem_simcom_sim7080: Data available on socket: 0
[00:00:40.359,893] <inf> net_mqtt_sock_tcp: Closing socket 0
[00:00:40.365,661] <inf> net_mqtt_publisher_sample: MQTT client disconnected -113
[00:00:40.933,349] <inf> modem_simcom_sim7080: +CAOPEN: 0
[00:00:40.943,298] <inf> net_mqtt: Connect completed

Environment:

• Window 11
• Zephyr version: Zephyr 3.4.0

[rlubos]

Looks as if an incomplete/malformed CONNACK was received. You can check if it's a TCP fragmentation issue by replacing

if (wait(APP_CONNECT_TIMEOUT_MS)) {

with

while (wait(APP_CONNECT_TIMEOUT_MS) > 0) {

here. If it helps, feel free to send a PR. If this doesn't help, it may be an issue with the offloaded socket implementation (which I'm not familiar with for this particular modem.

[ghost]

Hi @rlubos , I found out that when I comment out the block code:

packet_size = modem_socket_next_packet_size(&mdata.socket_config, sock);
if (!packet_size) {
if (flags & ZSOCK_MSG_DONTWAIT) {
errno = EAGAIN;
return -1;
}
modem_socket_wait_data(&mdata.socket_config, sock);
packet_size = modem_socket_next_packet_size(&mdata.socket_config, sock);
}

in simcom-sim7080.c file, I am able to connect with MQTT successfully:

660,919] net_mqtt_publisher_sample: Bye!
[00:00:49.661,010] net_mqtt_publisher_sample: attempting to connect:
[00:00:50.327,087] modem_simcom_sim7080: +CAOPEN: 0
[00:00:50.339,447] net_mqtt: Connect completed
[00:00:50.841,827] modem_simcom_sim7080: Data available on socket: 0
[00:00:50.850,830] net_mqtt_rx: err_code = 0
[00:00:50.850,830] net_mqtt_publisher_sample: MQTT client connected!
[00:00:50.850,860] net_mqtt_publisher_sample: try_to_connect: 0
[00:00:50.859,680] net_mqtt_publisher_sample: mqtt_ping: 0
[00:00:50.909,698] modem_simcom_sim7080: RSSI: -70
[00:00:51.169,982] modem_simcom_sim7080: Data available on socket: 0
[00:00:51.174,499] net_mqtt_rx: err_code = 0
[00:00:51.174,530] net_mqtt_publisher_sample: PINGRESP packet
[00:00:51.378,540] net_mqtt_publisher_sample: mqtt_publish: 0
[00:00:51.897,735] net_mqtt_publisher_sample: mqtt_publish: 0
[00:00:52.417,724] net_mqtt_publisher_sample: mqtt_publish: 0
[00:00:52.473,724] modem_simcom_sim7080: Data available on socket: 0
[00:00:52.482,574] net_mqtt_rx: err_code = 0

As far as I know, the driver does not support non-blocking sockets, leading to a lack of data segment when calling the driver layer and parsing wrong data when opening a new TCP connection and reading. That's why I comment out to force it to block and it works well.

[ghost]

Hi @rlubos , I found out that when I comment out the block code:

packet_size = modem_socket_next_packet_size(&mdata.socket_config, sock);
if (!packet_size) {
if (flags & ZSOCK_MSG_DONTWAIT) {
errno = EAGAIN;
return -1;
}
modem_socket_wait_data(&mdata.socket_config, sock);
packet_size = modem_socket_next_packet_size(&mdata.socket_config, sock);
}

in simcom-sim7080.c file, I am able to connect with MQTT successfully:

660,919] net_mqtt_publisher_sample: Bye!
[00:00:49.661,010] net_mqtt_publisher_sample: attempting to connect:
[00:00:50.327,087] modem_simcom_sim7080: +CAOPEN: 0
[00:00:50.339,447] net_mqtt: Connect completed
[00:00:50.841,827] modem_simcom_sim7080: Data available on socket: 0
[00:00:50.850,830] net_mqtt_rx: err_code = 0
[00:00:50.850,830] net_mqtt_publisher_sample: MQTT client connected!
[00:00:50.850,860] net_mqtt_publisher_sample: try_to_connect: 0
[00:00:50.859,680] net_mqtt_publisher_sample: mqtt_ping: 0
[00:00:50.909,698] modem_simcom_sim7080: RSSI: -70
[00:00:51.169,982] modem_simcom_sim7080: Data available on socket: 0
[00:00:51.174,499] net_mqtt_rx: err_code = 0
[00:00:51.174,530] net_mqtt_publisher_sample: PINGRESP packet
[00:00:51.378,540] net_mqtt_publisher_sample: mqtt_publish: 0
[00:00:51.897,735] net_mqtt_publisher_sample: mqtt_publish: 0
[00:00:52.417,724] net_mqtt_publisher_sample: mqtt_publish: 0
[00:00:52.473,724] modem_simcom_sim7080: Data available on socket: 0
[00:00:52.482,574] net_mqtt_rx: err_code = 0

As far as I know, the driver does not support non-blocking sockets, leading to a lack of data segment when calling the driver layer and parsing wrong data when opening a new TCP connection. That's why I comment out to force it to block and it works wells.