使用libcurl发送HTTP请求的一个简单示例代码

小咪咪 2022-05-25 06:43 319阅读 0赞

## 代码简单解释 ##

### 设置header ###

首先要声明header的结构体变量，然后设置对应header值，最后将其设置到curl结构体中

//声明
    CURL *curl;
    struct curl_slist *headers = NULL;
    
    //赋值header值
    headers = curl_slist_append(headers, "Host: 0xz.sz.qcloud.com");
    headers = curl_slist_append(headers, "yousa3: zym");
    
    //设置header
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

### 指定url ###

//声明url
    string url = "http://10.54.69.29:80/test/usr/loveqiqian";
    
    //指定url
    curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
    
    //发送http请求
    res = curl_easy_perform(curl);

### 设置HTTP请求的body ###

这里发送的请求是POST请求，通过如下代码设置的是POST请求  
`curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "POST");`

如果没有指定contenttype，那么contenttype默认是post的标准表单格式，application/x-www-form-urlencoded

设置body是如下代码：

//先用char[] 准备好要发送的body字符串
    char hello[12] = "a=hello";
    
    //设置body长度以及内容
    curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, strlen(hello));
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, hello);
    
    //然后就可以使用easy_perform接口发送了。

### 获取响应响应码 ###

res获取到的就是HTTP响应码

res = curl_easy_perform(curl);

### 获取响应header以及响应body ###

//声明
    string header;
    string result;
    
    //设置
    curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, &write_data);
    curl_easy_setopt(curl, CURLOPT_HEADERDATA, &header);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, &write_data);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &result);
    
    //write_data函数是这样
    size_t write_data(void *buffer, size_t size, size_t nmemb, void *userp){
        char *d = (char*)buffer;
        string *b = (string*)(userp);
        int result = 0;
        if (b != NULL){
            b->append(d, size*nmemb);
            result = size*nmemb;
        }
        return result;
    }

PS：HEAD请求的响应是没有body的，需要额外设置一行

`curl_easy_setopt(curl, CURLOPT_NOBODY, 1);`

## 代码 ##

#include <stdio.h>
    #include <iostream>
    #include <curl/curl.h>
    #include <string.h>
    
    using namespace std;
    
    size_t write_data(void *buffer, size_t size, size_t nmemb, void *userp);
    
    int main() {
        cout<<"hello world" << endl;
    
        CURL *curl;
        CURLcode res;
        curl = curl_easy_init();
        string url = "http://10.54.69.29:80/test/usr/loveqiqian";
        string header;
        string result;
        struct curl_slist *headers = NULL;
        char hello[12] = "a=hello";
    
    
    
        headers = curl_slist_append(headers, "Host: 0xz.sz.qcloud.com");
        headers = curl_slist_append(headers, "yousa3: zym");
    
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
    
        curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "POST");
        curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
    
        curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, strlen(hello));
        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, hello);
    
        curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, &write_data);
        curl_easy_setopt(curl, CURLOPT_HEADERDATA, &header);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, &write_data);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &result);
        curl_easy_setopt(curl, CURLOPT_TIMEOUT, 10);
        res = curl_easy_perform(curl);
    
        cout << header << endl << endl;
        cout << result << endl;
        cout << res << endl;
        curl_easy_cleanup(curl);
    
        return 0;
    
    }
    
    size_t write_data(void *buffer, size_t size, size_t nmemb, void *userp){
        char *d = (char*)buffer;
        string *b = (string*)(userp);
        int result = 0;
        if (b != NULL){
            b->append(d, size*nmemb);
            result = size*nmemb;
        }
        return result;
    }