做一个c语言的邮箱自动发送文件代码

以下是一个使用 C 语言发送邮件并自动附加文件的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>

#define SERVER "smtp.gmail.com"
#define PORT 587
#define USERNAME "your_email_address@gmail.com"
#define PASSWORD "your_password"
#define DEST_EMAIL "destination_email_address@example.com"
#define SUBJECT "Automatic email with attachment"
#define FILENAME "/path/to/attachment/file.txt"
#define BUFFER_SIZE 1024

int main() {
    // 创建 socket
    int sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock < 0) {
        perror("socket");
        exit(1);
    }

    // 建立连接
    struct sockaddr_in server;
    server.sin_family = AF_INET;
    server.sin_port = htons(PORT);
    server.sin_addr.s_addr = inet_addr(SERVER);
    if (connect(sock, (struct sockaddr*)&server, sizeof(server)) < 0) {
        perror("connect");
        exit(1);
    }

    // 接收欢迎信息
    char buffer[BUFFER_SIZE];
    memset(buffer, 0, BUFFER_SIZE);
    if (recv(sock, buffer, BUFFER_SIZE, 0) < 0) {
        perror("recv");
        exit(1);
    }
    printf("%s\n", buffer);

    // 发送 EHLO 命令
    char ehlo_command[BUFFER_SIZE];
    snprintf(ehlo_command, BUFFER_SIZE, "EHLO %s\r\n", SERVER);
    if (send(sock, ehlo_command, strlen(ehlo_command), 0) < 0) {
        perror("send");
        exit(1);
    }
    memset(buffer, 0, BUFFER_SIZE);
    if (recv(sock, buffer, BUFFER_SIZE, 0) < 0) {
        perror("recv");
        exit(1);
    }
    printf("%s\n", buffer);

    // 发送 STARTTLS 命令
    if (send(sock, "STARTTLS\r\n", strlen("STARTTLS\r\n"), 0) < 0) {
        perror("send");
        exit(1);
    }
    memset(buffer, 0, BUFFER_SIZE);
    if (recv(sock, buffer, BUFFER_SIZE, 0) < 0) {
        perror("recv");
        exit(1);
    }
    printf("%s\n", buffer);

    // SSL 加密
    SSL_CTX* ctx = SSL_CTX_new(TLS_client_method());
    SSL* ssl = SSL_new(ctx);
    SSL_set_fd(ssl, sock);
    if (SSL_connect(ssl) < 0) {
        perror("SSL_connect");
        exit(1);
    }

    // 发送 EHLO 命令
    if (SSL_write(ssl, ehlo_command, strlen(ehlo_command)) < 0) {
        perror("SSL_write");
        exit(1);
    }
    memset(buffer, 0, BUFFER_SIZE);
    if (SSL_read(ssl, buffer, BUFFER_SIZE) < 0) {
        perror("SSL_read");
        exit(1);
    }
    printf("%s\n", buffer);

    // 发送 AUTH LOGIN 命令
    if (SSL_write(ssl, "AUTH LOGIN\r\n", strlen("AUTH LOGIN\r\n")) < 0) {
        perror("SSL_write");
        exit(1);
    }
    memset(buffer, 0, BUFFER_SIZE);
    if (SSL_read(ssl, buffer, BUFFER_SIZE) < 0) {
        perror("SSL_read");
        exit(1);
    }
    printf("%s\n", buffer);

    // 发送用户名
    char encoded_username[BUFFER_SIZE];
    size_t len = b64_encode((const unsigned char*)USERNAME, strlen(USERNAME), encoded_username, BUFFER_SIZE);
    encoded_username[len] = '\0';
    if (SSL_write(ssl, encoded_username, strlen(encoded_username)) < 0) {
        perror("SSL_write");
        exit(1);
    }
    if (SSL_write(ssl, "\r\n", strlen("\r\n")) < 0) {
        perror("SSL_write");
        exit(1);
    }
    memset(buffer, 0, BUFFER_SIZE);
    if (SSL_read(ssl, buffer, BUFFER_SIZE) < 0) {
        perror("SSL_read");
        exit(1);
    }
    printf("%s\n", buffer);

    // 发送密码
    char encoded_password[BUFFER_SIZE];
    len = b64_encode((const unsigned char*)PASSWORD, strlen(PASSWORD), encoded_password, BUFFER_SIZE);
    encoded_password[len] = '\0';
    if (SSL_write(ssl, encoded_password, strlen(encoded_password)) < 0) {
        perror("SSL_write");
        exit(1);
    }
    if (SSL_write(ssl, "\r\n", strlen("\r\n")) < 0) {
        perror("SSL_write");
        exit(1);
    }
    memset(buffer, 0, BUFFER_SIZE);
    if (SSL_read(ssl, buffer, BUFFER_SIZE) < 0) {
        perror("SSL_read");
        exit(1);
    }
    printf("%s\n", buffer);

    // 发送 MAIL FROM 命令
    char mail_from_command[BUFFER_SIZE];
    snprintf(mail_from_command, BUFFER_SIZE, "MAIL FROM:<%s>\r\n", USERNAME);
    if (SSL_write(ssl, mail_from_command, strlen(mail_from_command)) < 0) {
        perror("SSL_write");
        exit(1);
    }
    memset(buffer, 0, BUFFER_SIZE);
    if (SSL_read(ssl, buffer, BUFFER_SIZE) < 0) {
        perror("SSL_read");
        exit(1);
    }
    printf("%s\n", buffer);

    // 发送 RCPT TO 命令
    char rcpt_to_command[BUFFER_SIZE];
    snprintf(rcpt_to_command, BUFFER_SIZE, "RCPT TO:<%s>\r\n", DEST_EMAIL);
    if (SSL_write(ssl, rcpt_to_command, strlen(rcpt_to_command)) < 0) {
        perror("SSL_write");
        exit(1);
    }
    memset(buffer, 0, BUFFER_SIZE);
    if (SSL_read(ssl, buffer, BUFFER_SIZE) < 0) {
        perror("SSL_read");
        exit(1);
    }
    printf("%s\n", buffer);

    // 发送 DATA 命令
    if (SSL_write(ssl, "DATA\r\n", strlen("DATA\r\n")) < 0) {
        perror("SSL_write");
        exit(1);
    }
    memset(buffer, 0, BUFFER_SIZE);
    if (SSL_read(ssl, buffer, BUFFER_SIZE) < 0) {
        perror("SSL_read");
        exit(1);
    }
    printf("%s\n", buffer);

    // 发送邮件内容
    char email_content[BUFFER_SIZE];
    snprintf(email_content, BUFFER_SIZE, "From: %s\r\nTo: %s\r\nSubject: %s\r\n\r\n", USERNAME, DEST_EMAIL, SUBJECT);
    if (SSL_write(ssl, email_content, strlen(email_content)) < 0) {
        perror("SSL_write");
        exit(1);
    }

    // 读取附件文件并发送
    FILE* fp = fopen(FILENAME, "rb");
    if (fp == NULL) {
        perror("fopen");
        exit(1);
    }
    size_t bytes_read;
    while ((bytes_read = fread(buffer, 1, BUFFER_SIZE, fp)) > 0) {
        if (SSL_write(ssl, buffer, bytes_read) < 0) {
            perror("SSL_write");
            exit(1);
        }
    }
    fclose(fp);

    // 发送结束符
    if (SSL_write(ssl, "\r\n.\r\n", strlen("\r\n.\r\n")) < 0) {
        perror("SSL_write");
        exit(1);
    }
    memset(buffer, 0, BUFFER_SIZE);
    if (SSL_read(ssl, buffer, BUFFER_SIZE) < 0) {
        perror("SSL_read");
        exit(1);
    }
    printf("%s\n", buffer);

    // 发送 QUIT 命令
    if (SSL_write(ssl, "QUIT\r\n", strlen("QUIT\r\n")) < 0) {
        perror("SSL_write");
        exit(1);
    }
    memset(buffer, 0, BUFFER_SIZE);
    if (SSL_read(ssl, buffer, BUFFER_SIZE) < 0) {
        perror("SSL_read");
        exit(1);
    }
    printf("%s\n", buffer);

    // 关闭连接
    SSL_shutdown(ssl);
    close(sock);
    return 0;
}

注意：这个示例代码依赖 OpenSSL 库，并且需要使用 base64 编码来发送用户名和密码。同时，您需要将示例代码中的常量值替换为您自己的邮箱地址、密码、收件人地址和文件路径。