为什么使用 paho.mqtt.c 发送此消息会导致分段错误？
Why is this message sent using paho.mqtt.c causing segmentation fault?
我正在尝试使用 MQTT 协议发送特定类型的消息。我正在使用 paho.mqtt.c 库，我的代理是 RabbitMQ 3.6.12，运行ning Erlang 20.0。我正在使用虚拟机 运行ning CentOS 6.9。
我首先尝试通过为我的特定消息类型创建一个结构来做到这一点，然后在问这个问题之前，我还尝试使用 JSON 来创建我的特定消息类型。我安装了 cJSON（来自 here）。
这是我使用 cJSON 的全部代码：
pubframe.c :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#include "../tools.c"
#include <cjson/cJSON.h>
#define ADDRESS "tcp://localhost:1883"
#define CLIENTID "MY_PUB"
#define TOPIC "MQTT/Test"
int main(int argc, char* argv[])
{
frame1 test = {42,"test"};
cJSON* frm = NULL;
frm = cJSON_CreateObject();
cJSON_AddNumberToObject(frm,"entier",test.E);
cJSON_AddStringToObject(frm,"string",test.S);
print_frame1(frm);
int i = cJSON_GetArraySize(frm);
printf("number of items in frame : %d\n",i);
cJSON* entier = NULL;
entier = cJSON_GetObjectItem(frm,"entier");
char* pt = cJSON_Print(entier);
printf("entier : %s\n",pt);
cJSON* str = NULL;
str = cJSON_GetObjectItem(frm,"string");
char* st = cJSON_Print(str);
printf("string : %s\n",st);
printf("size of message : %d\n",sizeof(cJSON));
MQTTClient publisher;
MQTTClient_connectOptions connexion = MQTTClient_connectOptions_initializer;
MQTTClient_message msg = msg_creation(frm,sizeof(cJSON),0,0);
MQTTClient_deliveryToken token;
int rc;
MQTTClient_create(&publisher, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);
connexion.cleansession = 1;
MQTTClient_setCallbacks(publisher, NULL, connlost, frame_json_arrvd, NULL);
if ((rc = MQTTClient_connect(publisher,&connexion)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
}
MQTTClient_publishMessage(publisher, TOPIC,&msg,NULL);
printf("Message sent!\n");
cJSON_Delete(frm);
MQTTClient_disconnect(publisher,10000);
MQTTClient_destroy(&publisher);
return rc;
}
subframe.c :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#include "../tools.c"
#include <cjson/cJSON.h>
#define ADDRESS "tcp://localhost:1883"
#define CLIENTID "ClientID"
#define TOPIC "MQTT/Test"
#define QOS 0
#define TIMEOUT 10000L
int main(int argc, char* argv[])
{
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
int rc;
int ch;
MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE, NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
MQTTClient_setCallbacks(client, NULL, connlost, frame_json_arrvd, NULL);
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
"Press Q<Enter> to quit\n\n", TOPIC, CLIENTID, QOS);
MQTTClient_subscribe(client, TOPIC, QOS);
do
{
ch = getchar();
} while(ch!='Q' && ch != 'q');
MQTTClient_disconnect(client, 10000);
MQTTClient_destroy(&client);
return rc;
}
tools.c :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sys/time.h>
#include <cjson/cJSON.h>
#include "MQTTClient.h"
int compteur;
// message frames
typedef struct frame1
{
int E;
char* S;
} frame1;
void print_frame1bis(frame1* F)
{
printf(" %s\n",F->S);
printf(" %d\n",F->E);
}
void print_frame1(cJSON* frame1)
{
char * str = cJSON_Print(frame1);
printf("%s\n",str);
}
int frame_json_arrvd(void* context, char* topicName, int topicLen, MQTTClient_message* msg)
{
cJSON* payload_ptr = NULL;
printf("size of message : %d\n",sizeof(msg->payload));
int j = cJSON_GetArraySize(msg->payload);
printf("ok\n");
printf("number of items in frame : %d\n",j);
payload_ptr = cJSON_CreateObject();
payload_ptr = msg->payload;
int i = cJSON_GetArraySize(payload_ptr);
printf("number of items in frame : %d\n",i);
print_frame1(payload_ptr);
cJSON_Delete(payload_ptr);
MQTTClient_freeMessage(&msg);
MQTTClient_free(topicName);
return 1;
}
// in case connexion is lost
void connlost(void *context, char *cause)
{
printf("\nConnection lost\n");
printf(" cause: %s\n", cause);
}
// create message
MQTTClient_message msg_creation(void* payload, int length, int qos, int retained)
{
MQTTClient_message pubmsg = MQTTClient_message_initializer;
pubmsg.payload = payload;
pubmsg.payloadlen = length;
pubmsg.qos = qos;
pubmsg.retained = retained;
return pubmsg;
}
订阅者的输出是
Subscribing to topic MQTT/Test
for client ClientID using QoS0
Press Q<Enter> to quit
size of message : 8
Segmentation fault (core dumped)
看来消息没有正确接收，因为订阅者在尝试获取项目数时立即崩溃。
这是我在 运行 gdb 时得到的结果，不确定是否有帮助。
Program terminated with signal 11, Segmentation fault.
#0 0x00007f4e49a8b63e in cJSON_GetArraySize () from /usr/lib64/libcjson.so.1
(gdb) bt
#0 0x00007f4e49a8b63e in cJSON_GetArraySize () from /usr/lib64/libcjson.so.1
#1 0x00000000004010c9 in frame_json_arrvd (context=0x0,
topicName=0x7f4e440009e4 "MQTT/Test", topicLen=0, msg=0x7f4e44000bb4)
at ../tools.c:110
#2 0x00007f4e49c962a5 in MQTTClient_run (n=<value optimized out>)
at src/MQTTClient.c:604
#3 0x000000378b807aa1 in start_thread (arg=0x7f4e49a83700) at pthread_create.c:301
#4 0x000000378b4e8bcd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:115
发布者的输出是
{
"entier": 42,
"string": "test"
}
number of items in frame : 2
entier : 42
string : "test"
size of message : 64
Message sent!
看来消息已正确创建。
我最近刚刚研究了 cJSON，所以我会继续调查以防我使用错误，但我们将不胜感激。
我试图按照评论中的建议缩小它的范围，但我不知道我能做什么，因为它在尝试访问消息的有效负载时立即崩溃。
请记住，我只是一名学生，在计算机科学方面的经验不超过一年。另外，英语不是我的母语，我希望我能清楚地解释自己。
问题已解决（有点）
我只是将整个消息帧作为字符串发送并在 msgarrvd 函数中对其进行解析：
pubframe.c :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#include "../tools.c"
#include <cjson/cJSON.h>
#define ADDRESS "tcp://localhost:1883"
#define CLIENTID "MY_PUB"
#define TOPIC "MQTT/Test"
volatile MQTTClient_deliveryToken deliveredtoken;
void delivered(void *context, MQTTClient_deliveryToken dt)
{
printf("Message with token value %d delivery confirmed\n", dt);
deliveredtoken = dt;
}
int main(int argc, char* argv[])
{
char* test = "{\"string\" : \"whatever\", \"entier\" : 42}";
MQTTClient publisher;
MQTTClient_connectOptions connexion = MQTTClient_connectOptions_initializer;
MQTTClient_message msg = msg_creation(test,strlen(test),0,0);
int rc;
MQTTClient_create(&publisher, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);
connexion.cleansession = 1;
MQTTClient_setCallbacks(publisher, NULL, connlost, frame_test_arrvd, NULL);
if ((rc = MQTTClient_connect(publisher,&connexion)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
}
MQTTClient_publishMessage(publisher, TOPIC,&msg,&token);
printf("Message sent!\n");
cJSON_Delete(frm);
MQTTClient_disconnect(publisher,10000);
MQTTClient_destroy(&publisher);
return rc;
}
tools.c :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sys/time.h>
#include <cjson/cJSON.h>
#include "MQTTClient.h"
// message frames
void print_frame1(cJSON* frame1)
{
char * str = cJSON_Print(frame1);
printf("%s\n",str);
}
int frame_test_arrvd(void* context, char* topicName, int topicLen, MQTTClient_message* msg)
{
printf("message original : %s\n",msg->payload);
cJSON* payload_ptr = cJSON_Parse(msg->payload);
print_frame1(payload_ptr);
int i = cJSON_GetArraySize(payload_ptr);
printf("number of items in frame : %d\n",i);
cJSON* entier = NULL;
entier = cJSON_GetObjectItem(payload_ptr,"entier");
char* pt = cJSON_Print(entier);
printf("entier : %s\n",pt);
cJSON* str = NULL;
str = cJSON_GetObjectItem(payload_ptr,"string");
char* st = cJSON_Print(str);
printf("string : %s\n",st);
cJSON_Delete(payload_ptr);
MQTTClient_freeMessage(&msg);
MQTTClient_free(topicName);
return 1;
}
// in case connexion is lost
void connlost(void *context, char *cause)
{
printf("\nConnection lost\n");
printf(" cause: %s\n", cause);
}
// create message
MQTTClient_message msg_creation(void* payload, int length, int qos, int retained)
{
MQTTClient_message pubmsg = MQTTClient_message_initializer;
pubmsg.payload = payload;
pubmsg.payloadlen = length;
pubmsg.qos = qos;
pubmsg.retained = retained;
return pubmsg;
}
subframe.c :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#include "../tools.c"
#include <cjson/cJSON.h>
#define ADDRESS "tcp://localhost:1883"
#define CLIENTID "ClientID"
#define TOPIC "MQTT/Test"
#define QOS 0
#define TIMEOUT 10000L
int main(int argc, char* argv[])
{
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
int rc;
int ch;
MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE, NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
MQTTClient_setCallbacks(client, NULL, connlost, frame_test_arrvd, NULL);
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
"Press Q<Enter> to quit\n\n", TOPIC, CLIENTID, QOS);
MQTTClient_subscribe(client, TOPIC, QOS);
do
{
ch = getchar();
} while(ch!='Q' && ch != 'q');
MQTTClient_disconnect(client, 10000);
MQTTClient_destroy(&client);
return rc;
}
这并不理想，因为我仍然想创建特定类型的消息，而且我还没有找出导致分段错误的原因，但这种方式效果很好。
更新
我找到了一种方法来创建特定类型的消息并仍然将它们作为字符串发送以在 msgarrvd 函数中解析它们，我刚刚创建了一个函数 cJSON_ToString 将 cJSON* 对象转换为字符串，所以我可以从任何我想要的结构创建一个 cJOSN，然后将它转换成一个字符串来发送它。
我正在尝试使用 MQTT 协议发送特定类型的消息。我正在使用 paho.mqtt.c 库，我的代理是 RabbitMQ 3.6.12，运行ning Erlang 20.0。我正在使用虚拟机 运行ning CentOS 6.9。 我首先尝试通过为我的特定消息类型创建一个结构来做到这一点，然后在问这个问题之前，我还尝试使用 JSON 来创建我的特定消息类型。我安装了 cJSON（来自 here）。
这是我使用 cJSON 的全部代码：
pubframe.c :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#include "../tools.c"
#include <cjson/cJSON.h>
#define ADDRESS "tcp://localhost:1883"
#define CLIENTID "MY_PUB"
#define TOPIC "MQTT/Test"
int main(int argc, char* argv[])
{
frame1 test = {42,"test"};
cJSON* frm = NULL;
frm = cJSON_CreateObject();
cJSON_AddNumberToObject(frm,"entier",test.E);
cJSON_AddStringToObject(frm,"string",test.S);
print_frame1(frm);
int i = cJSON_GetArraySize(frm);
printf("number of items in frame : %d\n",i);
cJSON* entier = NULL;
entier = cJSON_GetObjectItem(frm,"entier");
char* pt = cJSON_Print(entier);
printf("entier : %s\n",pt);
cJSON* str = NULL;
str = cJSON_GetObjectItem(frm,"string");
char* st = cJSON_Print(str);
printf("string : %s\n",st);
printf("size of message : %d\n",sizeof(cJSON));
MQTTClient publisher;
MQTTClient_connectOptions connexion = MQTTClient_connectOptions_initializer;
MQTTClient_message msg = msg_creation(frm,sizeof(cJSON),0,0);
MQTTClient_deliveryToken token;
int rc;
MQTTClient_create(&publisher, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);
connexion.cleansession = 1;
MQTTClient_setCallbacks(publisher, NULL, connlost, frame_json_arrvd, NULL);
if ((rc = MQTTClient_connect(publisher,&connexion)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
}
MQTTClient_publishMessage(publisher, TOPIC,&msg,NULL);
printf("Message sent!\n");
cJSON_Delete(frm);
MQTTClient_disconnect(publisher,10000);
MQTTClient_destroy(&publisher);
return rc;
}
subframe.c :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#include "../tools.c"
#include <cjson/cJSON.h>
#define ADDRESS "tcp://localhost:1883"
#define CLIENTID "ClientID"
#define TOPIC "MQTT/Test"
#define QOS 0
#define TIMEOUT 10000L
int main(int argc, char* argv[])
{
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
int rc;
int ch;
MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE, NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
MQTTClient_setCallbacks(client, NULL, connlost, frame_json_arrvd, NULL);
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
"Press Q<Enter> to quit\n\n", TOPIC, CLIENTID, QOS);
MQTTClient_subscribe(client, TOPIC, QOS);
do
{
ch = getchar();
} while(ch!='Q' && ch != 'q');
MQTTClient_disconnect(client, 10000);
MQTTClient_destroy(&client);
return rc;
}
tools.c :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sys/time.h>
#include <cjson/cJSON.h>
#include "MQTTClient.h"
int compteur;
// message frames
typedef struct frame1
{
int E;
char* S;
} frame1;
void print_frame1bis(frame1* F)
{
printf(" %s\n",F->S);
printf(" %d\n",F->E);
}
void print_frame1(cJSON* frame1)
{
char * str = cJSON_Print(frame1);
printf("%s\n",str);
}
int frame_json_arrvd(void* context, char* topicName, int topicLen, MQTTClient_message* msg)
{
cJSON* payload_ptr = NULL;
printf("size of message : %d\n",sizeof(msg->payload));
int j = cJSON_GetArraySize(msg->payload);
printf("ok\n");
printf("number of items in frame : %d\n",j);
payload_ptr = cJSON_CreateObject();
payload_ptr = msg->payload;
int i = cJSON_GetArraySize(payload_ptr);
printf("number of items in frame : %d\n",i);
print_frame1(payload_ptr);
cJSON_Delete(payload_ptr);
MQTTClient_freeMessage(&msg);
MQTTClient_free(topicName);
return 1;
}
// in case connexion is lost
void connlost(void *context, char *cause)
{
printf("\nConnection lost\n");
printf(" cause: %s\n", cause);
}
// create message
MQTTClient_message msg_creation(void* payload, int length, int qos, int retained)
{
MQTTClient_message pubmsg = MQTTClient_message_initializer;
pubmsg.payload = payload;
pubmsg.payloadlen = length;
pubmsg.qos = qos;
pubmsg.retained = retained;
return pubmsg;
}
订阅者的输出是
Subscribing to topic MQTT/Test
for client ClientID using QoS0
Press Q<Enter> to quit
size of message : 8
Segmentation fault (core dumped)
看来消息没有正确接收，因为订阅者在尝试获取项目数时立即崩溃。
这是我在 运行 gdb 时得到的结果，不确定是否有帮助。
Program terminated with signal 11, Segmentation fault.
#0 0x00007f4e49a8b63e in cJSON_GetArraySize () from /usr/lib64/libcjson.so.1
(gdb) bt
#0 0x00007f4e49a8b63e in cJSON_GetArraySize () from /usr/lib64/libcjson.so.1
#1 0x00000000004010c9 in frame_json_arrvd (context=0x0,
topicName=0x7f4e440009e4 "MQTT/Test", topicLen=0, msg=0x7f4e44000bb4)
at ../tools.c:110
#2 0x00007f4e49c962a5 in MQTTClient_run (n=<value optimized out>)
at src/MQTTClient.c:604
#3 0x000000378b807aa1 in start_thread (arg=0x7f4e49a83700) at pthread_create.c:301
#4 0x000000378b4e8bcd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:115
发布者的输出是
{
"entier": 42,
"string": "test"
}
number of items in frame : 2
entier : 42
string : "test"
size of message : 64
Message sent!
看来消息已正确创建。
我最近刚刚研究了 cJSON，所以我会继续调查以防我使用错误，但我们将不胜感激。 我试图按照评论中的建议缩小它的范围，但我不知道我能做什么，因为它在尝试访问消息的有效负载时立即崩溃。
请记住，我只是一名学生，在计算机科学方面的经验不超过一年。另外，英语不是我的母语，我希望我能清楚地解释自己。
问题已解决（有点）
我只是将整个消息帧作为字符串发送并在 msgarrvd 函数中对其进行解析：
pubframe.c :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#include "../tools.c"
#include <cjson/cJSON.h>
#define ADDRESS "tcp://localhost:1883"
#define CLIENTID "MY_PUB"
#define TOPIC "MQTT/Test"
volatile MQTTClient_deliveryToken deliveredtoken;
void delivered(void *context, MQTTClient_deliveryToken dt)
{
printf("Message with token value %d delivery confirmed\n", dt);
deliveredtoken = dt;
}
int main(int argc, char* argv[])
{
char* test = "{\"string\" : \"whatever\", \"entier\" : 42}";
MQTTClient publisher;
MQTTClient_connectOptions connexion = MQTTClient_connectOptions_initializer;
MQTTClient_message msg = msg_creation(test,strlen(test),0,0);
int rc;
MQTTClient_create(&publisher, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);
connexion.cleansession = 1;
MQTTClient_setCallbacks(publisher, NULL, connlost, frame_test_arrvd, NULL);
if ((rc = MQTTClient_connect(publisher,&connexion)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
}
MQTTClient_publishMessage(publisher, TOPIC,&msg,&token);
printf("Message sent!\n");
cJSON_Delete(frm);
MQTTClient_disconnect(publisher,10000);
MQTTClient_destroy(&publisher);
return rc;
}
tools.c :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sys/time.h>
#include <cjson/cJSON.h>
#include "MQTTClient.h"
// message frames
void print_frame1(cJSON* frame1)
{
char * str = cJSON_Print(frame1);
printf("%s\n",str);
}
int frame_test_arrvd(void* context, char* topicName, int topicLen, MQTTClient_message* msg)
{
printf("message original : %s\n",msg->payload);
cJSON* payload_ptr = cJSON_Parse(msg->payload);
print_frame1(payload_ptr);
int i = cJSON_GetArraySize(payload_ptr);
printf("number of items in frame : %d\n",i);
cJSON* entier = NULL;
entier = cJSON_GetObjectItem(payload_ptr,"entier");
char* pt = cJSON_Print(entier);
printf("entier : %s\n",pt);
cJSON* str = NULL;
str = cJSON_GetObjectItem(payload_ptr,"string");
char* st = cJSON_Print(str);
printf("string : %s\n",st);
cJSON_Delete(payload_ptr);
MQTTClient_freeMessage(&msg);
MQTTClient_free(topicName);
return 1;
}
// in case connexion is lost
void connlost(void *context, char *cause)
{
printf("\nConnection lost\n");
printf(" cause: %s\n", cause);
}
// create message
MQTTClient_message msg_creation(void* payload, int length, int qos, int retained)
{
MQTTClient_message pubmsg = MQTTClient_message_initializer;
pubmsg.payload = payload;
pubmsg.payloadlen = length;
pubmsg.qos = qos;
pubmsg.retained = retained;
return pubmsg;
}
subframe.c :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#include "../tools.c"
#include <cjson/cJSON.h>
#define ADDRESS "tcp://localhost:1883"
#define CLIENTID "ClientID"
#define TOPIC "MQTT/Test"
#define QOS 0
#define TIMEOUT 10000L
int main(int argc, char* argv[])
{
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
int rc;
int ch;
MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE, NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
MQTTClient_setCallbacks(client, NULL, connlost, frame_test_arrvd, NULL);
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
"Press Q<Enter> to quit\n\n", TOPIC, CLIENTID, QOS);
MQTTClient_subscribe(client, TOPIC, QOS);
do
{
ch = getchar();
} while(ch!='Q' && ch != 'q');
MQTTClient_disconnect(client, 10000);
MQTTClient_destroy(&client);
return rc;
}
这并不理想，因为我仍然想创建特定类型的消息，而且我还没有找出导致分段错误的原因，但这种方式效果很好。
更新
我找到了一种方法来创建特定类型的消息并仍然将它们作为字符串发送以在 msgarrvd 函数中解析它们，我刚刚创建了一个函数 cJSON_ToString 将 cJSON* 对象转换为字符串，所以我可以从任何我想要的结构创建一个 cJOSN，然后将它转换成一个字符串来发送它。