1、前言

起初使用的是Cmake + Visual Studio 2019进行编译，使用的时候出现ssl错误，刚开始因为是openssl版本问题但是，多次更换版本重新编译，还是不行，可能是微软那一套对开源项目支持不是很友好，但是网上也有编译成功的案例，最终决定改用Mingw这一套进行编译。

服务器日志信息：
2023-07-20T01:03:31: New client connected from as 3300000001 (p2, c1, k600, u’test1’).
2023-07-20T01:03:34: OpenSSL Error[0]: error:0A000126:SSL routines::unexpected eof while reading
2023-07-20T01:03:34: Client 3300000001 closed its connection.

2、按照Mingw环境

地址：https://sourceforge.net/projects/mingw-w64/files/
此处大坑，一定要选择posix的，不要选择win32，不然后面编译paho c++就会一直报错，下载好之后进行解压，并且将其添加到环境变量中

输入gcc -v有版本信息表示安装成功了

3、编译paho c

需要使用ssl验证，需要提前安装好openssl

3.1、ssl验证大坑

正常编译的情况使用会出现Cannot connect to MQTT server with SSL on windows

github错误地址：
https://github.com/eclipse/paho.mqtt.c/issues/1324

3.2、解决方法

解决地址：https://github.com/eclipse/paho.mqtt.c/pull/1353/files
将绿色部分添加到这个文件中

添加后的代码，如果使用我的建议和我的版本一致，以免出现问题（paho.mqtt.c-1.3.12）

/*******************************************************************************
 * Copyright (c) 2009, 2022 IBM Corp., Ian Craggs
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v2.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    https://www.eclipse.org/legal/epl-2.0/
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Ian Craggs, Allan Stockdill-Mander - initial implementation
 *    Ian Craggs - fix for bug #409702
 *    Ian Craggs - allow compilation for OpenSSL < 1.0
 *    Ian Craggs - fix for bug #453883
 *    Ian Craggs - fix for bug #480363, issue 13
 *    Ian Craggs - SNI support
 *    Ian Craggs - fix for issues #155, #160
 *******************************************************************************/

/**
 * @file
 * \brief SSL  related functions
 *
 */

#if defined(OPENSSL)

#include "SocketBuffer.h"
#include "MQTTClient.h"
#include "MQTTProtocolOut.h"
#include "SSLSocket.h"
#include "Log.h"
#include "StackTrace.h"
#include "Socket.h"

#include "Heap.h"

#include <string.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
#include <openssl/crypto.h>
#include <openssl/x509v3.h>
#if defined(_WIN32) || defined(_WIN64)
#include <wincrypt.h>
#endif

extern Sockets mod_s;

static int SSLSocket_error(char* aString, SSL* ssl, SOCKET sock, int rc, int (*cb)(const char *str, size_t len, void *u), void* u);
char* SSL_get_verify_result_string(int rc);
void SSL_CTX_info_callback(const SSL* ssl, int where, int ret);
char* SSLSocket_get_version_string(int version);
void SSL_CTX_msg_callback(
		int write_p,
		int version,
		int content_type,
		const void* buf, size_t len,
		SSL* ssl, void* arg);
int pem_passwd_cb(char* buf, int size, int rwflag, void* userdata);
int SSL_create_mutex(ssl_mutex_type* mutex);
int SSL_lock_mutex(ssl_mutex_type* mutex);
int SSL_unlock_mutex(ssl_mutex_type* mutex);
int SSL_destroy_mutex(ssl_mutex_type* mutex);
#if (OPENSSL_VERSION_NUMBER >= 0x010000000)
extern void SSLThread_id(CRYPTO_THREADID *id);
#else
extern unsigned long SSLThread_id(void);
#endif
extern void SSLLocks_callback(int mode, int n, const char *file, int line);
int SSLSocket_createContext(networkHandles* net, MQTTClient_SSLOptions* opts);
void SSLSocket_destroyContext(networkHandles* net);
void SSLSocket_addPendingRead(SOCKET sock);

/* 1 ~ we are responsible for initializing openssl; 0 ~ openssl init is done externally */
static int handle_openssl_init = 1;
static ssl_mutex_type* sslLocks = NULL;
static ssl_mutex_type sslCoreMutex;

/* Used to store MQTTClient_SSLOptions for TLS-PSK callback */
static int tls_ex_index_ssl_opts;

#if defined(_WIN32) || defined(_WIN64)
#define iov_len len
#define iov_base buf
#define snprintf _snprintf
#endif


#if defined(_WIN32) || defined(_WIN64)
/* Loads the Certs from Windows cert store */
int cryptoapi_ca_cert(SSL_CTX *ssl_ctx)
{
	HCERTSTORE cs;
	PCCERT_CONTEXT ctx = NULL;
	X509 *cert;
	char buf[128];

	cs = CertOpenSystemStore(0, "ROOT");
	if (cs == NULL)
	{
		Log(TRACE_PROTOCOL, -1, "CryptoAPI: failed to open system cert store 'ROOT': error=%d", (int)GetLastError());
		return -1;
	}

	while ((ctx = CertEnumCertificatesInStore(cs, ctx)))
	{
		cert = d2i_X509(NULL, (const unsigned char **)&ctx->pbCertEncoded, ctx->cbCertEncoded);
		if (cert == NULL)
		{
			Log(TRACE_PROTOCOL, -1, "CryptoAPI: Could not process X509 DER encoding for CA cert");
			continue;
		}

		X509_NAME_oneline(X509_get_subject_name(cert), buf, sizeof(buf));
		Log(TRACE_PROTOCOL, 1, "OpenSSL: Loaded CA certificate for system certificate store: subject='%s'", buf);

		if (!X509_STORE_add_cert(SSL_CTX_get_cert_store(ssl_ctx), cert))
			Log(TRACE_PROTOCOL, -1, "Failed to add ca_cert to OpenSSL certificate store");

		X509_free(cert);
	}

	if (!CertCloseStore(cs, 0))
		Log(TRACE_PROTOCOL, -1, "failed to close system cert store 'ROOT': error = %d", (int)GetLastError());

	return 0;
}
#endif


/**
 * Gets the specific error corresponding to SOCKET_ERROR
 * @param aString the function that was being used when the error occurred
 * @param sock the socket on which the error occurred
 * @param rc the return code
 * @param cb the callback function to be passed as first argument to ERR_print_errors_cb
 * @param u context to be passed as second argument to ERR_print_errors_cb
 * @return the specific TCP error code
 */
static int SSLSocket_error(char* aString, SSL* ssl, SOCKET sock, int rc, int (*cb)(const char *str, size_t len, void *u), void* u)
{
    int error;

    FUNC_ENTRY;
    if (ssl)
        error = SSL_get_error(ssl, rc);
    else
        error = ERR_get_error();
    if (error == SSL_ERROR_WANT_READ || error == SSL_ERROR_WANT_WRITE)
    {
		Log(TRACE_MIN, -1, "SSLSocket error WANT_READ/WANT_WRITE");
    }
    else
    {
        static char buf[120];

        if (strcmp(aString, "shutdown") != 0)
        	Log(TRACE_MIN, -1, "SSLSocket error %s(%d) in %s for socket %d rc %d errno %d %s\n", buf, error, aString, sock, rc, errno, strerror(errno));
        if (cb)
            ERR_print_errors_cb(cb, u);
		if (error == SSL_ERROR_SSL || error == SSL_ERROR_SYSCALL)
			error = SSL_FATAL;
    }
    FUNC_EXIT_RC(error);
    return error;
}

static struct
{
	int code;
	char* string;
}
X509_message_table[] =
{
	{ X509_V_OK, "X509_V_OK" },
	{ X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT, "X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT" },
	{ X509_V_ERR_UNABLE_TO_GET_CRL, "X509_V_ERR_UNABLE_TO_GET_CRL" },
	{ X509_V_ERR_UNABLE_TO_DECRYPT_CERT_SIGNATURE, "X509_V_ERR_UNABLE_TO_DECRYPT_CERT_SIGNATURE" },
	{ X509_V_ERR_UNABLE_TO_DECRYPT_CRL_SIGNATURE, "X509_V_ERR_UNABLE_TO_DECRYPT_CRL_SIGNATURE" },
	{ X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY, "X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY" },
	{ X509_V_ERR_CERT_SIGNATURE_FAILURE, "X509_V_ERR_CERT_SIGNATURE_FAILURE" },
	{ X509_V_ERR_CRL_SIGNATURE_FAILURE, "X509_V_ERR_CRL_SIGNATURE_FAILURE" },
	{ X509_V_ERR_CERT_NOT_YET_VALID, "X509_V_ERR_CERT_NOT_YET_VALID" },
	{ X509_V_ERR_CERT_HAS_EXPIRED, "X509_V_ERR_CERT_HAS_EXPIRED" },
	{ X509_V_ERR_CRL_NOT_YET_VALID, "X509_V_ERR_CRL_NOT_YET_VALID" },
	{ X509_V_ERR_CRL_HAS_EXPIRED, "X509_V_ERR_CRL_HAS_EXPIRED" },
	{ X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD, "X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD" },
	{ X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD, "X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD" },
	{ X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD, "X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD" },
	{ X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD, "X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD" },
	{ X509_V_ERR_OUT_OF_MEM, "X509_V_ERR_OUT_OF_MEM" },
	{ X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT, "X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT" },
	{ X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN, "X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN" },
	{ X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY, "X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY" },
	{ X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE, "X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE" },
	{ X509_V_ERR_CERT_CHAIN_TOO_LONG, "X509_V_ERR_CERT_CHAIN_TOO_LONG" },
	{ X509_V_ERR_CERT_REVOKED, "X509_V_ERR_CERT_REVOKED" },
	{ X509_V_ERR_INVALID_CA, "X509_V_ERR_INVALID_CA" },
	{ X509_V_ERR_PATH_LENGTH_EXCEEDED, "X509_V_ERR_PATH_LENGTH_EXCEEDED" },
	{ X509_V_ERR_INVALID_PURPOSE, "X509_V_ERR_INVALID_PURPOSE" },
	{ X509_V_ERR_CERT_UNTRUSTED, "X509_V_ERR_CERT_UNTRUSTED" },
	{ X509_V_ERR_CERT_REJECTED, "X509_V_ERR_CERT_REJECTED" },
	{ X509_V_ERR_SUBJECT_ISSUER_MISMATCH, "X509_V_ERR_SUBJECT_ISSUER_MISMATCH" },
	{ X509_V_ERR_AKID_SKID_MISMATCH, "X509_V_ERR_AKID_SKID_MISMATCH" },
	{ X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH, "X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH" },
	{ X509_V_ERR_KEYUSAGE_NO_CERTSIGN, "X509_V_ERR_KEYUSAGE_NO_CERTSIGN" },
	{ X509_V_ERR_UNABLE_TO_GET_CRL_ISSUER, "X509_V_ERR_UNABLE_TO_GET_CRL_ISSUER" },
	{ X509_V_ERR_UNHANDLED_CRITICAL_EXTENSION, "X509_V_ERR_UNHANDLED_CRITICAL_EXTENSION" },
	{ X509_V_ERR_KEYUSAGE_NO_CRL_SIGN, "X509_V_ERR_KEYUSAGE_NO_CRL_SIGN" },
	{ X509_V_ERR_UNHANDLED_CRITICAL_CRL_EXTENSION, "X509_V_ERR_UNHANDLED_CRITICAL_CRL_EXTENSION" },
	{ X509_V_ERR_INVALID_NON_CA, "X509_V_ERR_INVALID_NON_CA" },
	{ X509_V_ERR_PROXY_PATH_LENGTH_EXCEEDED, "X509_V_ERR_PROXY_PATH_LENGTH_EXCEEDED" },
	{ X509_V_ERR_KEYUSAGE_NO_DIGITAL_SIGNATURE, "X509_V_ERR_KEYUSAGE_NO_DIGITAL_SIGNATURE" },
	{ X509_V_ERR_PROXY_CERTIFICATES_NOT_ALLOWED, "X509_V_ERR_PROXY_CERTIFICATES_NOT_ALLOWED" },
	{ X509_V_ERR_INVALID_EXTENSION, "X509_V_ERR_INVALID_EXTENSION" },
	{ X509_V_ERR_INVALID_POLICY_EXTENSION, "X509_V_ERR_INVALID_POLICY_EXTENSION" },
	{ X509_V_ERR_NO_EXPLICIT_POLICY, "X509_V_ERR_NO_EXPLICIT_POLICY" },
	{ X509_V_ERR_UNNESTED_RESOURCE, "X509_V_ERR_UNNESTED_RESOURCE" },
#if defined(X509_V_ERR_DIFFERENT_CRL_SCOPE)
	{ X509_V_ERR_DIFFERENT_CRL_SCOPE, "X509_V_ERR_DIFFERENT_CRL_SCOPE" },
	{ X509_V_ERR_UNSUPPORTED_EXTENSION_FEATURE, "X509_V_ERR_UNSUPPORTED_EXTENSION_FEATURE" },
	{ X509_V_ERR_PERMITTED_VIOLATION, "X509_V_ERR_PERMITTED_VIOLATION" },
	{ X509_V_ERR_EXCLUDED_VIOLATION, "X509_V_ERR_EXCLUDED_VIOLATION" },
	{ X509_V_ERR_SUBTREE_MINMAX, "X509_V_ERR_SUBTREE_MINMAX" },
	{ X509_V_ERR_UNSUPPORTED_CONSTRAINT_TYPE, "X509_V_ERR_UNSUPPORTED_CONSTRAINT_TYPE" },
	{ X509_V_ERR_UNSUPPORTED_CONSTRAINT_SYNTAX, "X509_V_ERR_UNSUPPORTED_CONSTRAINT_SYNTAX" },
	{ X509_V_ERR_UNSUPPORTED_NAME_SYNTAX, "X509_V_ERR_UNSUPPORTED_NAME_SYNTAX" },
#endif
};

#if !defined(ARRAY_SIZE)
/**
 * Macro to calculate the number of entries in an array
 */
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#endif

char* SSL_get_verify_result_string(int rc)
{
	int i;
	char* retstring = "undef";

	for (i = 0; i < ARRAY_SIZE(X509_message_table); ++i)
	{
		if (X509_message_table[i].code == rc)
		{
			retstring = X509_message_table[i].string;
			break;
		}
	}
	return retstring;
}


void SSL_CTX_info_callback(const SSL* ssl, int where, int ret)
{
	if (where & SSL_CB_LOOP)
	{
		Log(TRACE_PROTOCOL, 1, "SSL state %s:%s:%s",
                  (where & SSL_ST_CONNECT) ? "connect" : (where & SSL_ST_ACCEPT) ? "accept" : "undef",
                    SSL_state_string_long(ssl), SSL_get_cipher_name(ssl));
	}
	else if (where & SSL_CB_EXIT)
	{
		Log(TRACE_PROTOCOL, 1, "SSL %s:%s",
                  (where & SSL_ST_CONNECT) ? "connect" : (where & SSL_ST_ACCEPT) ? "accept" : "undef",
                    SSL_state_string_long(ssl));
	}
	else if (where & SSL_CB_ALERT)
	{
		Log(TRACE_PROTOCOL, 1, "SSL alert %s:%s:%s",
                  (where & SSL_CB_READ) ? "read" : "write",
                    SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
	}
	else if (where & SSL_CB_HANDSHAKE_START)
	{
		Log(TRACE_PROTOCOL, 1, "SSL handshake started %s:%s:%s",
                  (where & SSL_CB_READ) ? "read" : "write",
                    SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
	}
	else if (where & SSL_CB_HANDSHAKE_DONE)
	{
		Log(TRACE_PROTOCOL, 1, "SSL handshake done %s:%s:%s",
                  (where & SSL_CB_READ) ? "read" : "write",
                    SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
		Log(TRACE_PROTOCOL, 1, "SSL certificate verification: %s",
                    SSL_get_verify_result_string(SSL_get_verify_result(ssl)));
	}
	else
	{
		Log(TRACE_PROTOCOL, 1, "SSL state %s:%s:%s", SSL_state_string_long(ssl),
                   SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret));
	}
}


char* SSLSocket_get_version_string(int version)
{
	int i;
	static char buf[20];
	char* retstring = NULL;
	static struct
	{
		int code;
		char* string;
	}
	version_string_table[] =
	{
		{ SSL2_VERSION, "SSL 2.0" },
		{ SSL3_VERSION, "SSL 3.0" },
		{ TLS1_VERSION, "TLS 1.0" },
#if defined(TLS2_VERSION)
		{ TLS2_VERSION, "TLS 1.1" },
#endif
#if defined(TLS3_VERSION)
		{ TLS3_VERSION, "TLS 1.2" },
#endif
	};

	for (i = 0; i < ARRAY_SIZE(version_string_table); ++i)
	{
		if (version_string_table[i].code == version)
		{
			retstring = version_string_table[i].string;
			break;
		}
	}

	if (retstring == NULL)
	{
		if (snprintf(buf, sizeof(buf), "%i", version) >= sizeof(buf))
			buf[sizeof(buf)-1] = '\0'; /* just in case of snprintf buffer overflow */
		retstring = buf;
	}
	return retstring;
}


void SSL_CTX_msg_callback(int write_p, int version, int content_type, const void* buf, size_t len,
        SSL* ssl, void* arg)
{

/*
called by the SSL/TLS library for a protocol message, the function arguments have the following meaning:

write_p
This flag is 0 when a protocol message has been received and 1 when a protocol message has been sent.

version
The protocol version according to which the protocol message is interpreted by the library. Currently, this is one of SSL2_VERSION, SSL3_VERSION and TLS1_VERSION (for SSL 2.0, SSL 3.0 and TLS 1.0, respectively).

content_type
In the case of SSL 2.0, this is always 0. In the case of SSL 3.0 or TLS 1.0, this is one of the ContentType values defined in the protocol specification (change_cipher_spec(20), alert(21), handshake(22); but never application_data(23) because the callback will only be called for protocol messages).

buf, len
buf points to a buffer containing the protocol message, which consists of len bytes. The buffer is no longer valid after the callback function has returned.

ssl
The SSL object that received or sent the message.

arg
The user-defined argument optionally defined by SSL_CTX_set_msg_callback_arg() or SSL_set_msg_callback_arg().

*/

	Log(TRACE_MINIMUM, -1, "%s %s %d buflen %d", (write_p ? "sent" : "received"),
		SSLSocket_get_version_string(version),
		content_type, (int)len);
}


int pem_passwd_cb(char* buf, int size, int rwflag, void* userdata)
{
	int rc = 0;

	FUNC_ENTRY;
	if (!rwflag)
	{
		strncpy(buf, (char*)(userdata), size);
		buf[size-1] = '\0';
		rc = (int)strlen(buf);
	}
	FUNC_EXIT_RC(rc);
	return rc;
}

int SSL_create_mutex(ssl_mutex_type* mutex)
{
	int rc = 0;

	FUNC_ENTRY;
#if defined(_WIN32) || defined(_WIN64)
	*mutex = CreateMutex(NULL, 0, NULL);
#else
	rc = pthread_mutex_init(mutex, NULL);
#endif
	FUNC_EXIT_RC(rc);
	return rc;
}

int SSL_lock_mutex(ssl_mutex_type* mutex)
{
	int rc = -1;

	/* don't add entry/exit trace points, as trace gets lock too, and it might happen quite frequently  */
#if defined(_WIN32) || defined(_WIN64)
	if (WaitForSingleObject(*mutex, INFINITE) != WAIT_FAILED)
#else
	if ((rc = pthread_mutex_lock(mutex)) == 0)
#endif
	rc = 0;

	return rc;
}

int SSL_unlock_mutex(ssl_mutex_type* mutex)
{
	int rc = -1;

	/* don't add entry/exit trace points, as trace gets lock too, and it might happen quite frequently  */
#if defined(_WIN32) || defined(_WIN64)
	if (ReleaseMutex(*mutex) != 0)
#else
	if ((rc = pthread_mutex_unlock(mutex)) == 0)
#endif
	rc = 0;

	return rc;
}

int SSL_destroy_mutex(ssl_mutex_type* mutex)
{
	int rc = 0;

	FUNC_ENTRY;
#if defined(_WIN32) || defined(_WIN64)
	rc = CloseHandle(*mutex);
#else
	rc = pthread_mutex_destroy(mutex);
#endif
	FUNC_EXIT_RC(rc);
	return rc;
}



#if (OPENSSL_VERSION_NUMBER >= 0x010000000)
extern void SSLThread_id(CRYPTO_THREADID *id)
{
#if defined(_WIN32) || defined(_WIN64)
	CRYPTO_THREADID_set_numeric(id, (unsigned long)GetCurrentThreadId());
#else
	CRYPTO_THREADID_set_numeric(id, (unsigned long)pthread_self());
#endif
}
#else
extern unsigned long SSLThread_id(void)
{
#if defined(_WIN32) || defined(_WIN64)
	return (unsigned long)GetCurrentThreadId();
#else
	return (unsigned long)pthread_self();
#endif
}
#endif

extern void SSLLocks_callback(int mode, int n, const char *file, int line)
{
	if (sslLocks)
	{
		if (mode & CRYPTO_LOCK)
			SSL_lock_mutex(&sslLocks[n]);
		else
			SSL_unlock_mutex(&sslLocks[n]);
	}
}


void SSLSocket_handleOpensslInit(int bool_value)
{
	handle_openssl_init = bool_value;
}


int SSLSocket_initialize(void)
{
	int rc = 0;
	/*int prc;*/
	int i;
	int lockMemSize;

	FUNC_ENTRY;

	if (handle_openssl_init)
	{
		if ((rc = SSL_library_init()) != 1)
			rc = -1;

		ERR_load_crypto_strings();
		SSL_load_error_strings();

		/* OpenSSL 0.9.8o and 1.0.0a and later added SHA2 algorithms to SSL_library_init().
		Applications which need to use SHA2 in earlier versions of OpenSSL should call
		OpenSSL_add_all_algorithms() as well. */

		OpenSSL_add_all_algorithms();

		lockMemSize = CRYPTO_num_locks() * sizeof(ssl_mutex_type);

		sslLocks = malloc(lockMemSize);
		if (!sslLocks)
		{
			rc = -1;
			goto exit;
		}
		else
			memset(sslLocks, 0, lockMemSize);

		for (i = 0; i < CRYPTO_num_locks(); i++)
		{
			/* prc = */SSL_create_mutex(&sslLocks[i]);
		}

#if (OPENSSL_VERSION_NUMBER >= 0x010000000)
		CRYPTO_THREADID_set_callback(SSLThread_id);
#else
		CRYPTO_set_id_callback(SSLThread_id);
#endif
		CRYPTO_set_locking_callback(SSLLocks_callback);

	}

	SSL_create_mutex(&sslCoreMutex);

	tls_ex_index_ssl_opts = SSL_get_ex_new_index(0, "paho ssl options", NULL, NULL, NULL);

exit:
	FUNC_EXIT_RC(rc);
	return rc;
}

void SSLSocket_terminate(void)
{
	FUNC_ENTRY;

	if (handle_openssl_init)
	{
		CRYPTO_set_locking_callback(NULL);
		ERR_free_strings();
		EVP_cleanup();
		if (sslLocks)
		{
			int i = 0;

			for (i = 0; i < CRYPTO_num_locks(); i++)
			{
				SSL_destroy_mutex(&sslLocks[i]);
			}
			free(sslLocks);
		}
	}

	SSL_destroy_mutex(&sslCoreMutex);

	FUNC_EXIT;
}

static unsigned int call_ssl_psk_cb(SSL *ssl, const char *hint, char *identity, unsigned int max_identity_len, unsigned char *psk, unsigned int max_psk_len)
{
	int rc = 0;

	FUNC_ENTRY;

	{
		SSL_CTX *ctx = SSL_get_SSL_CTX(ssl);
		MQTTClient_SSLOptions* opts = SSL_CTX_get_ex_data(ctx, tls_ex_index_ssl_opts);

		if (opts == NULL)
			goto exit;

		if (opts->ssl_psk_cb != NULL)
			rc = opts->ssl_psk_cb(hint, identity, max_identity_len, psk, max_psk_len, opts->ssl_psk_context);
	}
exit:
	FUNC_EXIT_RC(rc);
	return rc;
}

int SSLSocket_createContext(networkHandles* net, MQTTClient_SSLOptions* opts)
{
	int rc = 1;

	FUNC_ENTRY;
	if (net->ctx == NULL)
	{
#if (OPENSSL_VERSION_NUMBER >= 0x10100000L)
		net->ctx = SSL_CTX_new(TLS_client_method());
#else
		int sslVersion = MQTT_SSL_VERSION_DEFAULT;
		if (opts->struct_version >= 1) sslVersion = opts->sslVersion;
/* SSL_OP_NO_TLSv1_1 is defined in ssl.h if the library version supports TLSv1.1.
 * OPENSSL_NO_TLS1 is defined in opensslconf.h or on the compiler command line
 * if TLS1.x was removed at OpenSSL library build time via Configure options.
 */
		switch (sslVersion)
		{
		case MQTT_SSL_VERSION_DEFAULT:
			net->ctx = SSL_CTX_new(SSLv23_client_method()); /* SSLv23 for compatibility with SSLv2, SSLv3 and TLSv1 */
			break;
#if defined(SSL_OP_NO_TLSv1) && !defined(OPENSSL_NO_TLS1)
		case MQTT_SSL_VERSION_TLS_1_0:
			net->ctx = SSL_CTX_new(TLSv1_client_method());
			break;
#endif
#if defined(SSL_OP_NO_TLSv1_1) && !defined(OPENSSL_NO_TLS1)
		case MQTT_SSL_VERSION_TLS_1_1:
			net->ctx = SSL_CTX_new(TLSv1_1_client_method());
			break;
#endif
#if defined(SSL_OP_NO_TLSv1_2) && !defined(OPENSSL_NO_TLS1)
		case MQTT_SSL_VERSION_TLS_1_2:
			net->ctx = SSL_CTX_new(TLSv1_2_client_method());
			break;
#endif
		default:
			break;
		}
#endif
		if (net->ctx == NULL)
		{
			if (opts->struct_version >= 3)
				SSLSocket_error("SSL_CTX_new", NULL, net->socket, rc, opts->ssl_error_cb, opts->ssl_error_context);
			else
				SSLSocket_error("SSL_CTX_new", NULL, net->socket, rc, NULL, NULL);
			goto exit;
		}
	}

#if (OPENSSL_VERSION_NUMBER >= 0x10100000L)
	SSL_CTX_set_security_level(net->ctx, 1);
#endif

#if defined(_WIN32) || defined(_WIN64)
	if(cryptoapi_ca_cert(net->ctx) == 0)
		Log(TRACE_PROTOCOL, 1, "Windows CA certificates loaded");
	else
		Log(TRACE_PROTOCOL, -1, "Windows CA certificates not loaded");
#endif

	if (opts->keyStore)
	{
		if ((rc = SSL_CTX_use_certificate_chain_file(net->ctx, opts->keyStore)) != 1)
		{
			if (opts->struct_version >= 3)
				SSLSocket_error("SSL_CTX_use_certificate_chain_file", NULL, net->socket, rc, opts->ssl_error_cb, opts->ssl_error_context);
			else
				SSLSocket_error("SSL_CTX_use_certificate_chain_file", NULL, net->socket, rc, NULL, NULL);
			goto free_ctx; /*If we can't load the certificate (chain) file then loading the privatekey won't work either as it needs a matching cert already loaded */
		}

		if (opts->privateKey == NULL)
			opts->privateKey = opts->keyStore;   /* the privateKey can be included in the keyStore */

		if (opts->privateKeyPassword != NULL)
		{
			SSL_CTX_set_default_passwd_cb(net->ctx, pem_passwd_cb);
			SSL_CTX_set_default_passwd_cb_userdata(net->ctx, (void*)opts->privateKeyPassword);
		}

		/* support for ASN.1 == DER format? DER can contain only one certificate? */
		rc = SSL_CTX_use_PrivateKey_file(net->ctx, opts->privateKey, SSL_FILETYPE_PEM);
		if (opts->privateKey == opts->keyStore)
			opts->privateKey = NULL;
		if (rc != 1)
		{
			if (opts->struct_version >= 3)
				SSLSocket_error("SSL_CTX_use_PrivateKey_file", NULL, net->socket, rc, opts->ssl_error_cb, opts->ssl_error_context);
			else
				SSLSocket_error("SSL_CTX_use_PrivateKey_file", NULL, net->socket, rc, NULL, NULL);
			goto free_ctx;
		}
	}

	if (opts->trustStore || opts->CApath)
	{
		if ((rc = SSL_CTX_load_verify_locations(net->ctx, opts->trustStore, opts->CApath)) != 1)
		{
			if (opts->struct_version >= 3)
				SSLSocket_error("SSL_CTX_load_verify_locations", NULL, net->socket, rc, opts->ssl_error_cb, opts->ssl_error_context);
			else
				SSLSocket_error("SSL_CTX_load_verify_locations", NULL, net->socket, rc, NULL, NULL);
			goto free_ctx;
		}
	}
	else if (!opts->disableDefaultTrustStore)
	{
		if ((rc = SSL_CTX_set_default_verify_paths(net->ctx)) != 1)
		{
			if (opts->struct_version >= 3)
				SSLSocket_error("SSL_CTX_set_default_verify_paths", NULL, net->socket, rc, opts->ssl_error_cb, opts->ssl_error_context);
			else
				SSLSocket_error("SSL_CTX_set_default_verify_paths", NULL, net->socket, rc, NULL, NULL);
			goto free_ctx;
		}
	}

	if (opts->enabledCipherSuites)
	{
		if ((rc = SSL_CTX_set_cipher_list(net->ctx, opts->enabledCipherSuites)) != 1)
		{
			if (opts->struct_version >= 3)
				SSLSocket_error("SSL_CTX_set_cipher_list", NULL, net->socket, rc, opts->ssl_error_cb, opts->ssl_error_context);
			else
				SSLSocket_error("SSL_CTX_set_cipher_list", NULL, net->socket, rc, NULL, NULL);
			goto free_ctx;
		}
	}

#ifndef OPENSSL_NO_PSK
	if (opts->ssl_psk_cb != NULL)
	{
		SSL_CTX_set_ex_data(net->ctx, tls_ex_index_ssl_opts, opts);
		SSL_CTX_set_psk_client_callback(net->ctx, call_ssl_psk_cb);
	}
#endif

#if (OPENSSL_VERSION_NUMBER >= 0x010002000) /* 1.0.2 and later */
	if (opts->protos != NULL && opts->protos_len > 0)
	{
		/* SSL_CTX_set_alpn_protos() returns 0 on success as opposed to the other SSL functions,
		   so we need to flip the meaning of rc or the return code will be wrong. */
		if ((rc = SSL_CTX_set_alpn_protos(net->ctx, opts->protos, opts->protos_len)) != 0)
		{
			if (opts->struct_version >= 3)
				SSLSocket_error("SSL_CTX_set_alpn_protos", NULL, net->socket, rc, opts->ssl_error_cb, opts->ssl_error_context);
			else
				SSLSocket_error("SSL_CTX_set_alpn_protos", NULL, net->socket, rc, NULL, NULL);
			rc = 0; /* report an error according to the convention in other OpenSSL functions */
			goto free_ctx;
		}
		rc = 1; /* report success according to the convention in other OpenSSL functions */
	}
#endif

	SSL_CTX_set_mode(net->ctx, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);

	goto exit;
free_ctx:
	SSL_CTX_free(net->ctx);
	net->ctx = NULL;

exit:
	FUNC_EXIT_RC(rc);
	return rc;
}


int SSLSocket_setSocketForSSL(networkHandles* net, MQTTClient_SSLOptions* opts,
	const char* hostname, size_t hostname_len)
{
	int rc = 1;

	FUNC_ENTRY;

	if (net->ctx != NULL || (rc = SSLSocket_createContext(net, opts)) == 1)
	{
		char *hostname_plus_null;
		int i;

		SSL_CTX_set_info_callback(net->ctx, SSL_CTX_info_callback);
		SSL_CTX_set_msg_callback(net->ctx, SSL_CTX_msg_callback);
   		if (opts->enableServerCertAuth)
			SSL_CTX_set_verify(net->ctx, SSL_VERIFY_PEER, NULL);

		net->ssl = SSL_new(net->ctx);

		/* Log all ciphers available to the SSL sessions (loaded in ctx) */
		for (i = 0; ;i++)
		{
			const char* cipher = SSL_get_cipher_list(net->ssl, i);
			if (cipher == NULL)
				break;
			Log(TRACE_PROTOCOL, 1, "SSL cipher available: %d:%s", i, cipher);
		}
		if ((rc = (int)SSL_set_fd(net->ssl, (int)net->socket)) != 1) {
			if (opts->struct_version >= 3)
				SSLSocket_error("SSL_set_fd", net->ssl, net->socket, rc, opts->ssl_error_cb, opts->ssl_error_context);
			else
				SSLSocket_error("SSL_set_fd", net->ssl, net->socket, rc, NULL, NULL);
		}
		hostname_plus_null = malloc(hostname_len + 1u );
		if (hostname_plus_null)
		{
			MQTTStrncpy(hostname_plus_null, hostname, hostname_len + 1u);
			if ((rc = SSL_set_tlsext_host_name(net->ssl, hostname_plus_null)) != 1) {
				if (opts->struct_version >= 3)
					SSLSocket_error("SSL_set_tlsext_host_name", NULL, net->socket, rc, opts->ssl_error_cb, opts->ssl_error_context);
				else
					SSLSocket_error("SSL_set_tlsext_host_name", NULL, net->socket, rc, NULL, NULL);
			}
			free(hostname_plus_null);
		}
		else
			rc = PAHO_MEMORY_ERROR;
	}

	FUNC_EXIT_RC(rc);
	return rc;
}

/*
 * Return value: 1 - success, TCPSOCKET_INTERRUPTED - try again, anything else is failure
 */
int SSLSocket_connect(SSL* ssl, SOCKET sock, const char* hostname, int verify, int (*cb)(const char *str, size_t len, void *u), void* u)
{
	int rc = 0;

	FUNC_ENTRY;

	ERR_clear_error();
	rc = SSL_connect(ssl);
	if (rc != 1)
	{
		int error;
		error = SSLSocket_error("SSL_connect", ssl, sock, rc, cb, u);
		if (error == SSL_FATAL)
			rc = error;
		if (error == SSL_ERROR_WANT_READ || error == SSL_ERROR_WANT_WRITE)
			rc = TCPSOCKET_INTERRUPTED;
	}
#if (OPENSSL_VERSION_NUMBER >= 0x010002000) /* 1.0.2 and later */
	else if (verify)
	{
		char* peername = NULL;
		int port;
		size_t hostname_len;

		X509* cert = SSL_get_peer_certificate(ssl);
		hostname_len = MQTTProtocol_addressPort(hostname, &port, NULL, MQTT_DEFAULT_PORT);

		rc = X509_check_host(cert, hostname, hostname_len, 0, &peername);
		if (rc == 1)
			Log(TRACE_PROTOCOL, -1, "peername from X509_check_host is %s", peername);
		else
			Log(TRACE_PROTOCOL, -1, "X509_check_host for hostname %.*s failed, rc %d",
					(int)hostname_len, hostname, rc);

		if (peername != NULL)
			OPENSSL_free(peername);

		/* 0 == fail, -1 == SSL internal error, -2 == malformed input */
		if (rc == 0 || rc == -1 || rc == -2)
		{
			char* ip_addr = malloc(hostname_len + 1);
			/* cannot use = strndup(hostname, hostname_len); here because of custom Heap */
			if (ip_addr)
			{
				strncpy(ip_addr, hostname, hostname_len);
				ip_addr[hostname_len] = '\0';

				rc = X509_check_ip_asc(cert, ip_addr, 0);
				Log(TRACE_MIN, -1, "rc from X509_check_ip_asc is %d", rc);

				free(ip_addr);
			}

			if (rc == 0 || rc == -1 || rc == -2)
				rc = SSL_FATAL;
		}

		if (cert)
			X509_free(cert);
	}
#endif

	FUNC_EXIT_RC(rc);
	return rc;
}



/**
 *  Reads one byte from a socket
 *  @param socket the socket to read from
 *  @param c the character read, returned
 *  @return completion code
 */
int SSLSocket_getch(SSL* ssl, SOCKET socket, char* c)
{
	int rc = SOCKET_ERROR;

	FUNC_ENTRY;
	if ((rc = SocketBuffer_getQueuedChar(socket, c)) != SOCKETBUFFER_INTERRUPTED)
		goto exit;

	ERR_clear_error();
	if ((rc = SSL_read(ssl, c, (size_t)1)) < 0)
	{
		int err = SSLSocket_error("SSL_read - getch", ssl, socket, rc, NULL, NULL);
		if (err == SSL_ERROR_WANT_READ || err == SSL_ERROR_WANT_WRITE)
		{
			rc = TCPSOCKET_INTERRUPTED;
			SocketBuffer_interrupted(socket, 0);
		}
	}
	else if (rc == 0)
		rc = SOCKET_ERROR; 	/* The return value from recv is 0 when the peer has performed an orderly shutdown. */
	else if (rc == 1)
	{
		SocketBuffer_queueChar(socket, *c);
		rc = TCPSOCKET_COMPLETE;
	}
exit:
	FUNC_EXIT_RC(rc);
	return rc;
}



/**
 *  Attempts to read a number of bytes from a socket, non-blocking. If a previous read did not
 *  finish, then retrieve that data.
 *  @param socket the socket to read from
 *  @param bytes the number of bytes to read
 *  @param actual_len the actual number of bytes read
 *  @return completion code
 */
char *SSLSocket_getdata(SSL* ssl, SOCKET socket, size_t bytes, size_t* actual_len, int* rc)
{
	char* buf;

	FUNC_ENTRY;
	if (bytes == 0)
	{
		buf = SocketBuffer_complete(socket);
		goto exit;
	}

	buf = SocketBuffer_getQueuedData(socket, bytes, actual_len);

	if (*actual_len != bytes)
	{
		ERR_clear_error();
		if ((*rc = SSL_read(ssl, buf + (*actual_len), (int)(bytes - (*actual_len)))) < 0)
		{
			*rc = SSLSocket_error("SSL_read - getdata", ssl, socket, *rc, NULL, NULL);
			if (*rc != SSL_ERROR_WANT_READ && *rc != SSL_ERROR_WANT_WRITE)
			{
				buf = NULL;
				goto exit;
			}
		}
		else if (*rc == 0) /* rc 0 means the other end closed the socket */
		{
			buf = NULL;
			goto exit;
		}
		else
			*actual_len += *rc;
	}

	if (*actual_len == bytes)
	{
		SocketBuffer_complete(socket);
		/* if we read the whole packet, there might still be data waiting in the SSL buffer, which
		isn't picked up by select.  So here we should check for any data remaining in the SSL buffer, and
		if so, add this socket to a new "pending SSL reads" list.
		*/
		if (SSL_pending(ssl) > 0) /* return no of bytes pending */
			SSLSocket_addPendingRead(socket);
	}
	else /* we didn't read the whole packet */
	{
		SocketBuffer_interrupted(socket, *actual_len);
		Log(TRACE_MAX, -1, "SSL_read: %lu bytes expected but %lu bytes now received", bytes, *actual_len);
	}
exit:
	FUNC_EXIT;
	return buf;
}

void SSLSocket_destroyContext(networkHandles* net)
{
	FUNC_ENTRY;
	if (net->ctx)
		SSL_CTX_free(net->ctx);
	net->ctx = NULL;
	FUNC_EXIT;
}

static List pending_reads = {NULL, NULL, NULL, 0, 0};

int SSLSocket_close(networkHandles* net)
{
	int rc = 1;

	FUNC_ENTRY;
	/* clean up any pending reads for this socket */
	if (pending_reads.count > 0 && ListFindItem(&pending_reads, &net->socket, intcompare))
		ListRemoveItem(&pending_reads, &net->socket, intcompare);

	if (net->ssl)
	{
		ERR_clear_error();
		rc = SSL_shutdown(net->ssl);
		SSL_free(net->ssl);
		net->ssl = NULL;
	}
	SSLSocket_destroyContext(net);
	FUNC_EXIT_RC(rc);
	return rc;
}


/* No SSL_writev() provided by OpenSSL. Boo. */
int SSLSocket_putdatas(SSL* ssl, SOCKET socket, char* buf0, size_t buf0len, PacketBuffers bufs)
{
	int rc = 0;
	int i;
	char *ptr;
	iobuf iovec;
	int sslerror;

	FUNC_ENTRY;
	iovec.iov_len = (ULONG)buf0len;
	for (i = 0; i < bufs.count; i++)
		iovec.iov_len += (ULONG)bufs.buflens[i];

	ptr = iovec.iov_base = (char *)malloc(iovec.iov_len);
	if (!ptr)
	{
		rc = PAHO_MEMORY_ERROR;
		goto exit;
	}
	memcpy(ptr, buf0, buf0len);
	ptr += buf0len;
	for (i = 0; i < bufs.count; i++)
	{
		if (bufs.buffers[i] != NULL && bufs.buflens[i] > 0)
		{
			memcpy(ptr, bufs.buffers[i], bufs.buflens[i]);
			ptr += bufs.buflens[i];
		}
	}

	SSL_lock_mutex(&sslCoreMutex);
	ERR_clear_error();
	if ((rc = SSL_write(ssl, iovec.iov_base, iovec.iov_len)) == iovec.iov_len)
		rc = TCPSOCKET_COMPLETE;
	else
	{
		sslerror = SSLSocket_error("SSL_write", ssl, socket, rc, NULL, NULL);

		if (sslerror == SSL_ERROR_WANT_WRITE)
		{
			SOCKET* sockmem = (SOCKET*)malloc(sizeof(SOCKET));
			int free = 1;

			if (!sockmem)
			{
				rc = PAHO_MEMORY_ERROR;
				SSL_unlock_mutex(&sslCoreMutex);
				goto exit;
			}
			Log(TRACE_MIN, -1, "Partial write: incomplete write of %lu bytes on SSL socket %d",
				iovec.iov_len, socket);
			SocketBuffer_pendingWrite(socket, ssl, 1, &iovec, &free, iovec.iov_len, 0);
			*sockmem = socket;
			ListAppend(mod_s.write_pending, sockmem, sizeof(int));
#if defined(USE_SELECT)
			FD_SET(socket, &(mod_s.pending_wset));
#endif
			rc = TCPSOCKET_INTERRUPTED;
		}
		else
			rc = SOCKET_ERROR;
	}
	SSL_unlock_mutex(&sslCoreMutex);

	if (rc != TCPSOCKET_INTERRUPTED)
		free(iovec.iov_base);
	else
	{
		int i;
		free(buf0);
		for (i = 0; i < bufs.count; ++i)
		{
		    if (bufs.frees[i])
		    {
		    	free(bufs.buffers[i]);
		    	bufs.buffers[i] = NULL;
		    }
		}	
	}
exit:
	FUNC_EXIT_RC(rc);
	return rc;
}


void SSLSocket_addPendingRead(SOCKET sock)
{
	FUNC_ENTRY;
	if (ListFindItem(&pending_reads, &sock, intcompare) == NULL) /* make sure we don't add the same socket twice */
	{
		SOCKET* psock = (SOCKET*)malloc(sizeof(SOCKET));
		if (psock)
		{
			*psock = sock;
			ListAppend(&pending_reads, psock, sizeof(sock));
		}
	}
	else
		Log(TRACE_MIN, -1, "SSLSocket_addPendingRead: socket %d already in the list", sock);

	FUNC_EXIT;
}


SOCKET SSLSocket_getPendingRead(void)
{
	SOCKET sock = -1;

	if (pending_reads.count > 0)
	{
		sock = *(int*)(pending_reads.first->content);
		ListRemoveHead(&pending_reads);
	}
	return sock;
}


int SSLSocket_continueWrite(pending_writes* pw)
{
	int rc = 0;

	FUNC_ENTRY;
	ERR_clear_error();
	if ((rc = SSL_write(pw->ssl, pw->iovecs[0].iov_base, pw->iovecs[0].iov_len)) == pw->iovecs[0].iov_len)
	{
		/* topic and payload buffers are freed elsewhere, when all references to them have been removed */
		free(pw->iovecs[0].iov_base);
		Log(TRACE_MIN, -1, "SSL continueWrite: partial write now complete for socket %d", pw->socket);
		rc = 1;
	}
	else
	{
		int sslerror = SSLSocket_error("SSL_write", pw->ssl, pw->socket, rc, NULL, NULL);
		if (sslerror == SSL_ERROR_WANT_WRITE)
			rc = 0; /* indicate we haven't finished writing the payload yet */
	}
	FUNC_EXIT_RC(rc);
	return rc;
}


int SSLSocket_abortWrite(pending_writes* pw)
{
	int rc = 0;

	FUNC_ENTRY;
	free(pw->iovecs[0].iov_base);
	FUNC_EXIT_RC(rc);
	return rc;
}
#endif

可以开始编译了

选择刚才安装的mingw编译器的位置

还有其他的一些功能，可以按需要勾选和设置。
PAHO_BUILD_SAMPLES:构建样例
PAHO_BUILD_SHARED:生成动态库
PAHO_BUILD_SHARED：生成静态库
PAHO_ENABLE_TESTING:构建test样例
区域变成红色，然后我们可以勾选需要编译的功能，这里勾选PAHO_WITH_SS

经过cmake编译后，build文件夹中已经有了我们需要的文件，接着对其进行再次编译。如图所示
mingw32-make命令编译build

3.3、mingw32-make过程出现报错

这个错误主要是使用了Linux中的poll函数，但是poll函数不是一个跨平台的函数，Windows平台需要让他使用select所需需要定义这个宏

解决方法：Socket.c文件添加一行宏定义#if defined(USE_SELECT)

3.4、继续出错

找到对应的文件，在前面添加一行#define _WINDOWS

3.5、编译成功

paho.mqtt3a:a表示的是异步消息推送（asynchronous）
paho-mqtt3as ： as表示的是 异步+加密（asynchronous+OpenSSL）。
paho-mqtt3c ： c 表示的应该是同步（Synchronize），一般性能较差，是发送+等待模式。
paho-mqtt3cs ： 同上，增加了一个OpenSSL而已

于是在build文件夹下的src中，有了编译后的库文件，命令执行完成后可以再PAHO_INSTALL_PREFIX设置的路径下看到如下的文件

4、编译paho c++

前提先编译好paho c

打开cmake界面，添加源码路径和编译生成路径，如下图所示，点击configure

打开windows命令行进入build目录，输入mingw32-make进行编译。

5、Qt使用paho mqtt库

1、将paho c 和c++源代码中src中的头文件拷贝出来，将刚才编译好的库拷贝到链接的文件中

5.1、编码

widget.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include "mqtt/async_client.h"
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class mqttCall : public QObject, public virtual mqtt::callback
    , public virtual mqtt::iaction_listener
{
    Q_OBJECT
public:
    mqttCall() {}
    ~mqttCall() {}

public:
    virtual void connection_lost(const std::string& cause) {
        std::cout << "Connection lost: " << cause << std::endl;
    }

    virtual void delivery_complete(mqtt::delivery_token_ptr tok) {
        std::cout << "Delivery complete for token: " << (tok ? tok->get_message_id() : -1) << std::endl;
    }

    void message_arrived(mqtt::const_message_ptr msg) {
        std::cout << "topic:" << msg->get_topic() << std::endl;
        //        std::cout<<"Message:"<<msg->to_string()<<std::endl;
    }

    void connected(const std::string& cause) override {
        std::cout << "Connected to broker: " << cause << std::endl;
    }

    void on_failure(const mqtt::token& tok) {
        std::cout << "MQTT action failed" << std::endl;
    }

    void on_success(const mqtt::token& tok) {
        std::cout << "MQTT action succeeded" << std::endl;
    }
};

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

public:
    mqtt::async_client client_;
    mqttCall cb_;
    QString topic_;
private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

widget.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <qdebug.h>
#define QOS 2

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
    , client_("ssl://autove.xxxxxx.com:8883", "3300000031")
    , topic_("/down/info")
{
    ui->setupUi(this);

    client_.set_callback(cb_);

    mqtt::connect_options connOpts;
    connOpts.set_clean_session(true);
    connOpts.set_user_name("xxxx");
    connOpts.set_password("xxxxx");
    connOpts.set_keep_alive_interval(600);

    mqtt::ssl_options sslOpts;
    sslOpts.set_ssl_version(MQTT_SSL_VERSION_TLS_1_2);
    sslOpts.set_verify(false);
    connOpts.set_ssl(sslOpts);

    try
    {
        mqtt::token_ptr conntok = client_.connect(connOpts);
        conntok->wait();

        mqtt::token_ptr subtok = client_.subscribe(topic_.toStdString(), QOS, nullptr, cb_);
        subtok->wait();
    }
    catch (const mqtt::exception& exc) {
        qDebug() << "-----------------" << endl;
        qDebug()<< exc.what();
        qDebug()<<"connect faile";
    }
}

MainWindow::~MainWindow()
{
    delete ui;
}