一、json-c

json是一种轻量级的数据交换格式，json选用完全独立于语言的文本格局，。

jdon格式

json数据的书写格式是键/值对

json键值对用来保存js对象的一种方式，键/值对包括字段名称（在双引号中），后面写一个冒号，然后是值。

JSON 值可以是：字符串（在双引号中）、数组（在中括号中）、数字（整数或浮点数）、逻辑值（true 或 false）、对象（在大括号中）、 null。

Json结构

json结构有两种，就是对象和数组，通过这两种结构可以表示各种复杂的结构：

{"province": "Shanxi"} 可以理解为是一个包含province为Shanxi的对象，

["Shanxi","Shandong"]这是一个包含两个元素的数组

而 [{"province": "Shanxi"},{"province": "Shandong"}] 就表示包含两个对象的数组。

当然了,你也可以使用 {"province":["Shanxi","Shandong"]} 来简化上面的JSON,这是一个拥有一个name数组的对象。

下面是一小段JSON代码：

{“skillz”: {“web”:[ {“name”: “html”， “years”: “5” }， {“name”: “css”， “years”: “3” }],”database”:[ {“name”: “sql”， “years”: “7” }]}}

花括弧，方括弧，冒号和逗号

花括弧表示一个“容器”

方括号装载数组

名称和值用冒号隔开

数组元素通过逗号隔开

json-c数据类型

typedef enum json_type {/* If you change this, be sure to update json_type_to_name() too */json_type_null,json_type_boolean,json_type_double,json_type_int,json_type_object,json_type_array,json_type_string,
} json_type;

基础API

struct json_object * json_object_new_object();//创建个空的json_type_object类型的JSON对象struct json_object* json_object_new_boolean(Boolean b);//创建个json_type_boolean值类型json对象int json_object_get_int(struct json_object *obj);//从json对象中int值类型得到int值struct json_object * json_object_new_array();//创建个空的json_type_array类型JSON数组值对象struct json_object * json_tokener_parse(char *str);//由str里的JSON字符串生成JSON对象，str是json_object_to_json_string() 生成的。
参数：str :json字符串struct json_object * json_object_object_get(struct json_object * json,char *name);//从json中按名字取一个对象。参数：json :json对象name : json域名字Int json_object_is_type(struct json_object * this, enum json_type type)//检查json_object是json的某个类型参数：this: json_object 实例type: json_type_boolean,json_type_double, json_type_int, json_type_object, json_type_array, json_type_stringvoid json_object_object_add(struct json_object* obj, char *key, struct json_object *val);//添加个对象域到json对象中参数：Obj – json对象key – 域名字val – json值对象void json_object_object_del(struct json_object* obj, char *key);//删除key值json对象参数：obj – json对象key – 域名字int json_object_array_length(struct json_object *obj);//得到json对象数组的长度参数：ob j – json数组值对象

二、保活机制

音响作为客户端每隔5s向服务器发送一个数据包，证明自己还活着

数据报json格式

5s使用闹钟函数alarm，他可以在进程中设置一个定时器。他向进程发送SIGALRM信号。可以设置忽略或者不捕获此信号，如果采用默认方式其动作是终止调用该alarm函数的进程。

所需头文件

#include<unistd.h>

函数原型

unsigned int alarm（unsigned int seconds);

函数参数

seconds:指定秒数

函数返回值

成功：如果调用此alarm（）前，进程已经设置了闹钟时间，则返回上一个闹钟时间的剩余时间，否则返回0。

出错：-1

在socket.c中设置

void *connect_cb(void *arg)
{int count = 5, ret;struct sockaddr_in server_addr;memset(&server_addr, 0, sizeof(server_addr));server_addr.sin_family = PF_INET;server_addr.sin_port = htons(SERVER_PORT);server_addr.sin_addr.s_addr = inet_addr(SERVER_IP);while (count--){ret = connect(g_sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr));if (ret == -1){sleep(5);continue;}//连接成功，点亮 4 个LED灯led_on(0);led_on(1);led_on(2);led_on(3);alarm(TIMEOUT);signal(SIGALRM, send_server);break；
}

调用send_server向服务器发送数据包

数据交互：

1. 保活

客户端：{“status”：“alive”}；

socket.c

//5秒执行一次，向服务器发送 alive 字符串
void send_server(int sig)
{struct json_object *json = json_object_new_object();//创建json对象json_object_object_add(json, "status", json_object_new_string("alive"));//添加保活键值json_object_object_add(json, "deviceid", json_object_new_string("001"));//设备idconst char *buf = json_object_to_json_string(json);//将json格式转化为string对象int ret = send(g_sockfd, buf, strlen(buf), 0); //将json格式字符串发送给服务器if (-1 == ret){perror("send");}1alarm(5);//循环调用，一直发送保活
}

三、开始播放

2、开始播放

服务器发送：{“cmd”：“start”}；

select.c改进

void m_select()
{show();fd_set tmpfd;int ret;char message[1024] = {0};//接收服务器消息while (1){tmpfd = readfd;ret = select(g_maxfd + 1, &tmpfd, NULL, NULL, NULL);if (-1 == ret && errno != EINTR){perror("select");}else if (-1 == ret && errno == EINTR){continue;}if (FD_ISSET(g_sockfd, &tmpfd))           //TCP有数据可读{memset(message, 0, sizeof(message));//清空接收消息ret = recv(g_sockfd, message, sizeof(message), 0);//将服务器发送来的消息保存到message中if (-1 == ret){perror("recv");}char cmd[64] = {0};parse_message(message, cmd);//解析服务器的数据放到cmd中if (!strcmp(cmd, "start"))//根据服务器不同的消息，执行不同的功能{socket_start_play();            }else if (!strcmp(cmd, "stop")){socket_stop_play();}else if (!strcmp(cmd, "suspend")){socket_suspend_play();}else if (!strcmp(cmd, "continue")){socket_continue_play();}else if (!strcmp(cmd, "prior")){socket_prior_play();}else if (!strcmp(cmd, "next")){socket_next_play();}else if (!strcmp(cmd, "voice_up")){socket_voice_up_play();}else if (!strcmp(cmd, "voice_down")){socket_voice_down_play();}else if (!strcmp(cmd, "sequence")){socket_mode_play(SEQUENCEMODE);}else if (!strcmp(cmd, "random")){socket_mode_play(RANDOM);}else if (!strcmp(cmd, "circle")){socket_mode_play(CIRCLE);}else if (!strcmp(cmd, "get"))     //获取状态{    socket_get_status();}else if (!strcmp(cmd, "music"))   //获取所有音乐{socket_get_music();                                }}

按键按了app怎么同步

服务器每隔一秒获取播放器的状态

app上线获取所有音乐：

get获取状态

music获取所有音乐

字符串转为json对象

void parse_message(const char *m, char *c)
{struct json_object *obj = json_tokener_parse(m);//将符合json格式的字符串构造为一个json对象struct json_object *json;//json_object_object_get_ex(obj, "cmd", &json);json = json_object_object_get(obj, "cmd");//从json中获取键cmd的值strcpy(c, json_object_get_string(json));将获取的值拷贝给c
}

player.h声明

#ifndef PLAYER_H
#define PLAYER_H#include <unistd.h>#define MUSICPATH   "/root/music_list/"#define SHMKEY     1234
#define SHMSIZE    4096#define SEQUENCEMODE    1
#define RANDOM          2
#define CIRCLE          3//共享内存数据
struct shm
{int play_mode;char cur_name[64];pid_t ppid;pid_t child_pid;pid_t grand_pid;
};
typedef struct shm shm;int InitShm();
void GetMusic();
void start_play();
void stop_play();
void suspend_play();
void continue_play();
void prior_play();
void next_play();
void voice_up();
void voice_down();
void set_mode(int mode);#endif

socket.h

#ifndef SOCKET_H
#define SOCKET_H#define SERVER_PORT   8000
#define SERVER_IP     "47.101.128.140"
//#define SERVER_IP    "127.0.0.1"
#define TIMEOUT       1int InitSocket();
void socket_start_play();
void socket_stop_play();
void socket_suspend_play();
void socket_continue_play();
void socket_prior_play();
void socket_next_play();
void socket_voice_up_play();
void socket_voice_down_play();
void socket_mode_play(int);
void socket_get_status();
void socket_get_music();#endif

开始播放回复一个消息给服务器

服务器发送：{“cmd”：“start”}；

客户端回复：{“result”：“start_success”}；

socket.c

void socket_start_play()//服务器调用开始播放
{start_play();//开始播放struct json_object *json = json_object_new_object(); //创建json对象json_object_object_add(json, "cmd", json_object_new_string("reply"));//向json对象添加cmdjson_object_object_add(json, "result", json_object_new_string("start_success"));//添加resultconst char *buf = json_object_to_json_string(json);//转化为json对象int ret = send(g_sockfd, buf, strlen(buf), 0);//发送给服务器if (-1 == ret){perror("send");}
}
void socket_stop_play()
{stop_play();struct json_object *json = json_object_new_object();json_object_object_add(json, "cmd", json_object_new_string("reply"));json_object_object_add(json, "result", json_object_new_string("stop_success"));const char *buf = json_object_to_json_string(json);int ret = send(g_sockfd, buf, strlen(buf), 0);if (-1 == ret){perror("send");}
}void socket_suspend_play()
{suspend_play();struct json_object *json = json_object_new_object();json_object_object_add(json, "cmd", json_object_new_string("reply"));json_object_object_add(json, "result", json_object_new_string("suspend_success"));const char *buf = json_object_to_json_string(json);int ret = send(g_sockfd, buf, strlen(buf), 0);if (-1 == ret){perror("send");}
}void socket_continue_play()
{continue_play();struct json_object *json = json_object_new_object();json_object_object_add(json, "cmd", json_object_new_string("reply"));json_object_object_add(json, "result", json_object_new_string("continue_success"));const char *buf = json_object_to_json_string(json);int ret = send(g_sockfd, buf, strlen(buf), 0);if (-1 == ret){perror("send");}
}void socket_prior_play()
{prior_play();struct json_object *json = json_object_new_object();json_object_object_add(json, "cmd", json_object_new_string("reply"));json_object_object_add(json, "result", json_object_new_string("success"));const char *buf = json_object_to_json_string(json);int ret = send(g_sockfd, buf, strlen(buf), 0);if (-1 == ret){perror("send");}
}void socket_next_play()
{next_play();struct json_object *json = json_object_new_object();json_object_object_add(json, "cmd", json_object_new_string("reply"));json_object_object_add(json, "result", json_object_new_string("success"));const char *buf = json_object_to_json_string(json);int ret = send(g_sockfd, buf, strlen(buf), 0);if (-1 == ret){perror("send");}
}void socket_mode_play(int mode)
{set_mode(mode);struct json_object *json = json_object_new_object();json_object_object_add(json, "cmd", json_object_new_string("reply"));json_object_object_add(json, "result", json_object_new_string("success"));const char *buf = json_object_to_json_string(json);int ret = send(g_sockfd, buf, strlen(buf), 0);if (-1 == ret){perror("send");}
}

更新交换数据

socket.c

void send_server(int sig)
{struct json_object *json = json_object_new_object();json_object_object_add(json, "cmd", json_object_new_string("info"));json_object_object_add(json, "status", json_object_new_string("alive"));json_object_object_add(json, "deviceid", json_object_new_string("001"));const char *buf = json_object_to_json_string(json);int ret = send(g_sockfd, buf, strlen(buf), 0);if (-1 == ret){perror("send");}alarm(5);
}

socket.c

void socket_get_status()
{//播放状态  当前歌曲名  音量struct json_object *json = json_object_new_object();json_object_object_add(json, "cmd", json_object_new_string("reply_status"));if (g_start_flag == 1 && g_suspend_flag == 0){json_object_object_add(json, "status", json_object_new_string("start"));}else if (g_start_flag == 1 && g_suspend_flag == 1){json_object_object_add(json, "status", json_object_new_string("suspend"));}else if (g_start_flag == 0){json_object_object_add(json, "status", json_object_new_string("stop"));}json_object_object_add(json, "voice", json_object_new_int(iLeft));shm s;memset(&s, 0, sizeof(s));memcpy(&s, g_addr, sizeof(s));json_object_object_add(json, "music", json_object_new_string(s.cur_name));const char *buf = json_object_to_json_string(json);int ret = send(g_sockfd, buf, strlen(buf), 0);if (-1 == ret){perror("send");}
}