curl向web服务器发送json数据

c++使用libcurl：

/*
 *g++ demo.cpp  -g -Wall -lcurl
 */

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <iostream>
#include <curl/curl.h>

int getUrl(const char* filename)
{
    CURL* curl;
    CURLcode res;
    FILE* fp; 
    if((fp=fopen(filename, "w"))==NULL){
        return -1; 
    }   
    struct curl_slist *headers = NULL;
    headers = curl_slist_append(headers, "Accept:Agent-007");
    curl = curl_easy_init();    
    if(curl){
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
        curl_easy_setopt(curl, CURLOPT_URL, "http://www.baidu.com");
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
        curl_easy_setopt(curl, CURLOPT_HEADERDATA, fp);

        //0: success, other: failure
        res = curl_easy_perform(curl);
        if(res != 0){ 
            std::cout <<"error:"<<curl_easy_strerror(res) << std::endl;
        }
        curl_slist_free_all(headers);
        curl_easy_cleanup(curl);
        fclose(fp);
    }
    return res;
}

/*
int postUrl(const char* filename)
{
    CURL* curl;
    CURLcode res;
    FILE* fp;

    if((fp=fopen(filename, "w"))==NULL){
        return 1;
    }
    curl = curl_easy_init();
    if(curl){
    
    }
}
*/

//typedef  int  (* func)(int,  int);
typedef  size_t (*cb_func)(void*, size_t, size_t, void*);
size_t write_data(void *buffer, size_t size, size_t nmemb, void *userp) {
    FILE *fptr = (FILE*)userp;
    fwrite(buffer, size, nmemb, fptr);
    return size*nmemb;
}

int PostData(const char* postdata, const char* url,
             cb_func write_data, void* fptr)
//int PostData(const char* postdata, const char* url)
{
    CURL* curl = NULL;
    CURLcode res;
    char tmp[32] = {0};
    struct curl_slist* headers = NULL;
    if(!url){
        return -1;
    }
    std::cout <<"send data url:" << url << std::endl;
    snprintf(tmp, sizeof(tmp), "Content-Length: %d", (int)strlen(postdata));
    std::cout <<"Content-Length: " << tmp << std::endl;
    headers = curl_slist_append(headers, "Accept: application/json");
    headers = curl_slist_append(headers, "Content-Type: application/json");
    headers = curl_slist_append(headers, "charset: utf-8");
    headers = curl_slist_append(headers, tmp);

    curl_global_init(CURL_GLOBAL_ALL);
    curl = curl_easy_init();
    if(curl){
        curl_easy_setopt(curl, CURLOPT_URL,url);
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
        curl_easy_setopt(curl, CURLOPT_TIMEOUT, 1); //超时时间1s
        curl_easy_setopt(curl, CURLOPT_POST, 1L);
        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, postdata);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, fptr);
        //curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);   //debug 
        res = curl_easy_perform(curl);
        if(res!=0){
            std::cout<<"error no:"<<curl_easy_strerror(res)<<std::endl;
        }
        curl_slist_free_all(headers);
        curl_easy_cleanup(curl);
        return res;
    }else{
        curl_slist_free_all(headers);
        return -2;
    }
}

int main()
{
    const char* tt = "./aa.out";
    int aa =  getUrl(tt);
    std::cout << "return :" << aa << std::endl;
    FILE* fptr;
    if((fptr=fopen("./result", "w"))==NULL){
        std::cout << "file open error" << std::endl;
        exit(1);
    }

    const char* jsondata = "{"usrname": "cp", "passwd": "test"}";
     const char* url = "http://192.168.2.163:8080/mystorage/mytest.php";
    aa = PostData(jsondata, url, write_data, fptr);
    return 0;
}