通过C中的服务器和客户端应用程序中的套接字发送和接收JSON [英] send and receive JSON over sockets in server and client application in C
问题描述
我想通过服务器客户端中的套接字通过JSON发送数据 用C编写的应用程序.
I want to send the data in JSON over sockets in a server-client application written in C.
我正在使用 json-c/libjson 用于在C中处理JSON数据的库 应用程序.
I am using json-c / libjson library for handling JSON data in C application.
通过研究一些教程，我能够创建JSON对象并能够成功解析它.
By working on some of the tutorials I am able to create JSON object and able to parse it successfully.
现在，我想使用JSON数据格式进行服务器-客户端的通信.
Now I want to use the JSON data format for the communication of server-client.
这是我的服务器和客户端代码的一部分
Here is part of my server and client code
server.c
int main()
{
int listenfd = 0, connfd = 0; //related with the server
struct sockaddr_in serv_addr;
//json_object * jobj;
uint8_t buf[158], i;
memset(&buf, '0', sizeof(buf));
listenfd = socket(AF_INET, SOCK_STREAM, 0);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
serv_addr.sin_port = htons(8888);
bind(listenfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr));
printf("binding\n");
listen(listenfd, 5);
printf("listening\n");
connfd = accept(listenfd, (struct sockaddr*)NULL, NULL);
printf("Reading from client\n");
while ( (read(connfd, buf, 157)) > 0 )
{
for ( i = 0; i < 157; i++ )
//printf("%s\n", json_object_to_json_string(jobj));
//json_parse(jobj);
printf("%d\n", buf[i]);
}
return 0;
}
client.c
int main()
{
char* str;
int fd = 0;
struct sockaddr_in demoserverAddr;
fd = socket(AF_INET, SOCK_STREAM, 0);
if (fd < 0)
{
printf("Error : Could not create socket\n");
return 1;
}
else
{
demoserverAddr.sin_family = AF_INET;
demoserverAddr.sin_port = htons(8888);
demoserverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
memset(demoserverAddr.sin_zero, '\0', sizeof(demoserverAddr.sin_zero));
}
if (connect(fd, (const struct sockaddr *)&demoserverAddr, sizeof(demoserverAddr)) < 0)
{
printf("ERROR connecting to server\n");
return 1;
}
/*Creating a json object*/
json_object *jobj = json_object_new_object();
/*Creating a json string*/
json_object *jstring = json_object_new_string("Joys of Programming");
/*Creating a json integer*/
json_object *jint = json_object_new_int(10);
/*Creating a json boolean*/
json_object *jboolean = json_object_new_boolean(1);
/*Creating a json double*/
json_object *jdouble = json_object_new_double(2.14);
/*Creating a json array*/
json_object *jarray = json_object_new_array();
/*Creating json strings*/
json_object *jstring1 = json_object_new_string("c");
json_object *jstring2 = json_object_new_string("c++");
json_object *jstring3 = json_object_new_string("php");
/*Adding the above created json strings to the array*/
json_object_array_add(jarray,jstring1);
json_object_array_add(jarray,jstring2);
json_object_array_add(jarray,jstring3);
/*Form the json object*/
/*Each of these is like a key value pair*/
json_object_object_add(jobj,"Site Name", jstring);
json_object_object_add(jobj,"Technical blog", jboolean);
json_object_object_add(jobj,"Average posts per day", jdouble);
json_object_object_add(jobj,"Number of posts", jint);
json_object_object_add(jobj,"Categories", jarray);
printf("Size of JSON object- %lu\n", sizeof(jobj));
printf("Size of JSON_TO_STRING- %lu,\n %s\n", sizeof(json_object_to_json_string(jobj)), json_object_to_json_string(jobj));
//printf("Size of string- %lu\n", sizeof(json_object_to_json_string(jobj)));
write(fd, json_object_to_json_string(jobj), 157);
printf("Written data\n");
return 0;
}
我想将json_object jobj从客户端发送到服务器. 该怎么做?
I want to send the json_object jobj from client to server. How to do this?
我尝试过的一些事情:
-
当我使用
write(fd, jobj, sizeof(jobj))时，在服务器上接收数据时，客户端仅发送8个字节，其他字符为空.
When I use
write(fd, jobj, sizeof(jobj)), the client sends only 8 bytes and other characters are null when I receive data on server.
当我使用write(fd, json_object_to_json_string(jobj), 157)时，我只能发送完整的json_object jobj，其中157是该jobj对象中的字符总数.
I am only able to send complete json_object jobj when I use write(fd, json_object_to_json_string(jobj), 157) where 157 is the total number of characters in that jobj object.
如果在服务器端使用read(connfd, jobj, sizeof(jobj))，则只能接收8个字节(在客户端，我使用write(fd, jobj, sizeof(jobj))).
On server side if I use read(connfd, jobj, sizeof(jobj)) then I only able to receive 8 bytes (on client side I am using write(fd, jobj, sizeof(jobj))).
如果使用上述server.c，则可以接收完整的JSON对象(如果我已经知道该对象中的字符数).但这是原始格式(逐字节接收).
If I use the above server.c, I am able to receive complete JSON object (if I already know the number of characters in that object). But it is in raw format (receiving byte by byte).
如何从客户端发送完整的json_object jobj?
How to send the complete json_object jobj from client side?
以及如何在服务器端接收完整的json_object jobj?
And how to receive the complete json_object jobj on server side?
推荐答案
1)jobj是指针，因此在使用时
1) jobj is a pointer, so when you use
write(fd, jobj, sizeof(jobj))
您正在为该对象而不是该对象写一个指针.
you're writing a pointer to that object, not that object.
3)和以前一样.
也许您应该尝试用类似的方式发送它
Maybe you should try sending it with something like
if (write(fd, jobj, sizeof(*jobj)) == -1)
/* error handler /*
在接收端，您应该执行for循环，例如
On the receive side, you should do a for loop, like
for (;;)
{
r = read(fd, jobj, SIZE);
if (r == -1)
/*error handler*/
if (r == 0)
break;
}
如果您知道json的最大大小，请结合使用 malloc()和 realloc()否则
if you know the maximum SIZE of the json, or combine malloc() and realloc() otherwise
我做到了，现在可以正常工作了.
I did this, and now it works fine.
client.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <json/json.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
int main()
{
/* all previous code until
printf("Size of string- %lu\n", sizeof(json_object_to_json_string(jobj)))*/
char temp_buff[MAX_SIZE];
if (strcpy(temp_buff, json_object_to_json_string(jobj)) == NULL)
{
perror("strcpy");
return EXIT_FAILURE;
}
if (write(fd, temp_buff, strlen(temp_buff)) == -1)
{
perror("write");
return EXIT_FAILURE;
}
printf("Written data\n");
return EXIT_SUCCESS;
}
server.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <json/json.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
int main()
{
/* all previous code until
printf("Reading from client\n"); */
ssize_t r;
char buff[MAX_SIZE];
for (;;)
{
r = read(connfd, buff, MAX_SIZE);
if (r == -1)
{
perror("read");
return EXIT_FAILURE;
}
if (r == 0)
break;
printf("READ: %s\n", buff);
}
return EXIT_SUCCESS;
}
MAX_SIZE是一个宏，它指定最大缓冲区长度，并根据需要设置.
下次请粘贴所有代码(包括#include ...)并正确缩进.
MAX_SIZE is a macro that specifies the maximum buffer length, set it as you wish.
Please next time paste ALL your code (including the #include ...) and indent it properly.
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