C语言写一个可直接运行的简单电子邮件接收与发送代码

以下是一个简单的C代码示例，用于接收与发送电子邮件，需要使用libcurl库：

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

#define SMTP_SERVER "smtp.gmail.com"
#define SMTP_PORT 587

#define IMAP_SERVER "imap.gmail.com"
#define IMAP_PORT 993

#define EMAIL_ADDRESS "your_email@gmail.com"
#define EMAIL_PASSWORD "your_email_password"

void send_email(char *to, char *subject, char *body, char *file) {
    CURL *curl;
    CURLcode res = CURLE_OK;
    struct curl_slist *recipients = NULL;
    struct curl_slist *headers = NULL;
    struct curl_httppost *formpost = NULL;
    struct curl_httppost *lastptr = NULL;

    curl_global_init(CURL_GLOBAL_ALL);

    curl = curl_easy_init();

    if (curl) {
        // Set recipient
        recipients = curl_slist_append(recipients, to);
        curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);

        // Set email headers
        headers = curl_slist_append(headers, "Content-Type: multipart/mixed");
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

        // Set email body
        curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "subject", CURLFORM_COPYCONTENTS, subject, CURLFORM_END);
        curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "body", CURLFORM_COPYCONTENTS, body, CURLFORM_END);

        if (file) {
            curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "file", CURLFORM_FILE, file, CURLFORM_END);
        }

        curl_easy_setopt(curl, CURLOPT_URL, "smtps://" SMTP_SERVER ":" SMTP_PORT);
        curl_easy_setopt(curl, CURLOPT_USE_SSL, (long) CURLUSESSL_ALL);
        curl_easy_setopt(curl, CURLOPT_USERNAME, EMAIL_ADDRESS);
        curl_easy_setopt(curl, CURLOPT_PASSWORD, EMAIL_PASSWORD);
        curl_easy_setopt(curl, CURLOPT_MAIL_FROM, EMAIL_ADDRESS);
        curl_easy_setopt(curl, CURLOPT_READFUNCTION, NULL);
        curl_easy_setopt(curl, CURLOPT_MAIL_AUTH, CURLAUTH_LOGIN);
        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
        curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
        curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);

        res = curl_easy_perform(curl);

        if (res != CURLE_OK) {
            fprintf(stderr, "Failed to send email: %s\n", curl_easy_strerror(res));
        } else {
            printf("Email sent successfully.\n");
        }

        curl_slist_free_all(recipients);
        curl_slist_free_all(headers);
        curl_easy_cleanup(curl);
        curl_formfree(formpost);
    }
}

void receive_email() {
    CURL *curl;
    CURLcode res = CURLE_OK;
    struct curl_slist *headers = NULL;

    curl_global_init(CURL_GLOBAL_ALL);

    curl = curl_easy_init();

    if (curl) {
        // Set email headers
        headers = curl_slist_append(headers, "Content-Type: text/plain");
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

        curl_easy_setopt(curl, CURLOPT_USERNAME, EMAIL_ADDRESS);
        curl_easy_setopt(curl, CURLOPT_PASSWORD, EMAIL_PASSWORD);
        curl_easy_setopt(curl, CURLOPT_URL, "imaps://" IMAP_SERVER ":" IMAP_PORT "/INBOX");
        curl_easy_setopt(curl, CURLOPT_USE_SSL, (long) CURLUSESSL_ALL);
        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);

        res = curl_easy_perform(curl);

        if (res != CURLE_OK) {
            fprintf(stderr, "Failed to receive email: %s\n", curl_easy_strerror(res));
        }

        curl_slist_free_all(headers);
        curl_easy_cleanup(curl);
    }
}

int main() {
    send_email("recipient@example.com", "Test email", "This is a test email.", "test.jpg");
    receive_email();
    return 0;
}

请记得将`EMAIL_ADDRESS`和`EMAIL_PASSWORD`更改为您自己的电子邮件地址和密码，以及将`SMTP_SERVER`和`IMAP_SERVER`更改为您的电子邮件提供商的SMTP和IMAP服务器。同时，确保您已经安装了libcurl库，并在编译时链接了它。