MQTT Client Connection Closes Immediately

[NathanielDayLewis]

Hi,

v7.17

I'm having trouble getting the mongoose MQTT client to stay connected. The project I'm working on was built with the Wizard for Nucleo-H743ZI baremetal Make. The ultimate goal is to connect to Azure IoT Hub broker (which requires TLS), but I'm also testing with a HiveMQ Cluster. I haven't had success with the built-in TLS implementation, so I've been using MbedTLS v2.28.2.

I've been able to connect and complete authentication for both Azure IoT Hub and the HiveMQ Cluster, but the connection almost always closes immediately after processing the CONNACK despite a return code of 0. I made some modifications to mg_tls_recv in mongoose.c that kept the connection to HiveMQ alive (not closing when mbedtls_ssl_read returns 0), but haven't found an approach that keeps the connection to Azure IoT Hub open.

Does anyone have tips on how to troubleshoot this issue? Do my configurations look appropriate?

I'm running a separate client on my PC with python and paho.mqtt and haven't had any issues staying connected to either broker. I'm also monitoring the traffic with Wireshark.

Please let me know if there is any other information I can provide to contextualize my problem. Thanks in advance for your help!

mongoose_config.h

#pragma once

// See https://mongoose.ws/documentation/#build-options
#define MG_ARCH MG_ARCH_NEWLIB
#define MG_TLS MG_TLS_MBED
#define MG_OTA MG_OTA_STM32H7

#define MG_ENABLE_TCPIP 1
#define MG_ENABLE_CUSTOM_MILLIS 1
#define MG_ENABLE_CUSTOM_RANDOM 1
#define MG_ENABLE_DRIVER_STM32H 1
#define MG_ENABLE_PACKED_FS 1

// #define MG_DRIVER_MDC_CR 4   // RMII MDC clock divider, from 0 to 5
// #define MG_TCPIP_PHY_ADDR 0  // PHY address

// For static IP configuration, define MG_TCPIP_{IP,MASK,GW}
// By default, those are set to zero, meaning that DHCP is used
//
// #define MG_TCPIP_IP MG_IPV4(192, 168, 0, 10)     // IP
// #define MG_TCPIP_GW MG_IPV4(192, 168, 0, 1)      // Gateway
// #define MG_TCPIP_MASK MG_IPV4(255, 255, 255, 0)  // Netmask

// Construct MAC address from the MCU unique ID. It is defined in the
// ST CMSIS header as UID_BASE
#define MGUID ((uint32_t *) 0x1ff1e800)  // Unique 96-bit chip ID
#define MG_SET_MAC_ADDRESS(mac)      \
  do {                               \
    mac[0] = 2;                      \
    mac[1] = MGUID[0] & 255;         \
    mac[2] = (MGUID[0] >> 10) & 255; \
    mac[3] = (MGUID[0] >> 19) & 255; \
    mac[4] = MGUID[1] & 255;         \
    mac[5] = MGUID[2] & 255;         \
  } while (0)

mbedtls_config.h

/* Workaround for some mbedtls source files using INT_MAX without including limits.h */
#include <limits.h>

/* Config values from mongoose example */
#define MBEDTLS_NO_PLATFORM_ENTROPY
#define MBEDTLS_ENTROPY_HARDWARE_ALT
#define MBEDTLS_SSL_OUT_CONTENT_LEN    2048
#define MBEDTLS_ALLOW_PRIVATE_ACCESS
#define MBEDTLS_HAVE_TIME
#define MBEDTLS_SSL_SESSION_TICKETS

#define MBEDTLS_CIPHER_MODE_CBC
#define MBEDTLS_ECP_DP_SECP256R1_ENABLED
#define MBEDTLS_KEY_EXCHANGE_RSA_ENABLED
#define MBEDTLS_PKCS1_V15
#define MBEDTLS_SHA256_SMALLER
#define MBEDTLS_SSL_SERVER_NAME_INDICATION
#define MBEDTLS_AES_C
#define MBEDTLS_ASN1_PARSE_C
#define MBEDTLS_BIGNUM_C
#define MBEDTLS_CIPHER_C
#define MBEDTLS_CTR_DRBG_C
#define MBEDTLS_ENTROPY_C
#define MBEDTLS_ERROR_C
#define MBEDTLS_MD_C
#define MBEDTLS_MD5_C
#define MBEDTLS_OID_C
#define MBEDTLS_PKCS5_C
#define MBEDTLS_PK_C
#define MBEDTLS_PK_PARSE_C
#define MBEDTLS_PLATFORM_C
#define MBEDTLS_RSA_C
#define MBEDTLS_SHA1_C
#define MBEDTLS_SHA224_C
#define MBEDTLS_SHA256_C
#define MBEDTLS_SHA512_C
#define MBEDTLS_SSL_CLI_C
#define MBEDTLS_SSL_SRV_C
#define MBEDTLS_SSL_TLS_C
#define MBEDTLS_X509_CRT_PARSE_C
#define MBEDTLS_X509_USE_C
#define MBEDTLS_AES_FEWER_TABLES
#define MBEDTLS_PEM_PARSE_C
#define MBEDTLS_BASE64_C
#define MBEDTLS_SSL_TICKET_C

#define MBEDTLS_SSL_PROTO_TLS1_2
#define MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED
#define MBEDTLS_GCM_C
#define MBEDTLS_ECDH_C
#define MBEDTLS_ECP_C
#define MBEDTLS_ECDSA_C
#define MBEDTLS_ASN1_WRITE_C

// #define MBEDTLS_DEBUG_C

[scaprile]

Our built-in TLS is 1.3; HiveMQ does not seem to support that
I'm sorry, we are not MbedTLS experts, we can't check your config. There are some of them proven to work in the tutorials section in the repo https://github.com/cesanta/mongoose/blob/master/tutorials/stm32/nucleo-h743zi-make-baremetal-builtin/mbedtls_config.h
Our customers do not need to modify mongoose. No one should need to. Please see our documentation, and follow the guidelines in our tutorials.

Our examples work; MQTT is tested on every change and every night with a CI/CD pipeline. If something does not work for you, then please
sniff your network (using Wireshark, for example) and observe the traffic.
If, after your network inspection, you find an actual issue, feel free to open an issue, fill the issue template, and provide us with pertinent information (including useful network capture files; no snapshots, please attach capture files) in order to reproduce and fix the issue. We don't inspect your code for errors, please send the minimum piece of code that can reproduce the issue
https://mongoose.ws/documentation/tutorials/mqtt/mqtt-client/
https://mongoose.ws/documentation/tutorials/tls/

$ make
cc main.c mongoose.c  packed_fs.c       -W -Wall -Wextra -g -I.   -DMG_ENABLE_LINES=1 -DMG_ENABLE_PACKED_FS=1  -o example                                    
./example                    
be34c40 2 main.c:29:fn                  1 CREATED
be34e38 2 main.c:44:fn                  1 CONNECTED to mqtt://broker.hivemq.com:1883
be34e38 2 main.c:50:fn                  1 SUBSCRIBED to mg/+/test
be34e38 2 main.c:58:fn                  1 PUBLISHED hello -> mg/clnt/test
be34f29 2 main.c:63:fn                  1 RECEIVED hello <- mg/clnt/test
^Cbe36b65 2 main.c:65:fn                  1 CLOSED

$ make clean
rm -rf                    example                    *.o *.obj *.exe *.dSYM mbedtls
$ make CFLAGS_EXTRA="-DMG_TLS=MG_TLS_MBED -lmbedtls -lmbedcrypto -lmbedx509"
cc main.c mongoose.c  packed_fs.c       -W -Wall -Wextra -g -I.   -DMG_ENABLE_LINES=1 -DMG_ENABLE_PACKED_FS=1 -DMG_TLS=MG_TLS_MBED -lmbedtls -lmbedcrypto -lmbedx509 -o example                                    
$ ./example -u mqtts://broker.hivemq.com:8883
be51428 2 main.c:29:fn                  1 CREATED
be517fd 2 main.c:44:fn                  1 CONNECTED to mqtts://broker.hivemq.com:8883
be517fd 2 main.c:50:fn                  1 SUBSCRIBED to mg/+/test
be517fd 2 main.c:58:fn                  1 PUBLISHED hello -> mg/clnt/test
be518ee 2 main.c:63:fn                  1 RECEIVED hello <- mg/clnt/test
^Cbe52cf6 2 main.c:65:fn                  1 CLOSED