C语言实现发送邮件功能

#include <stdio.h>
#include <stdlib.h>
#include "winsock2.h"

extern int Base64Encod(char * data,char *output,int len,int *oputlen);

#define EMAIL_SERVER     "smtp.126.com"  //按需修改

int CreateSocketAndConnect()
{
    struct sockaddr_in server_addr;
    struct hostent *Addr;
    int ret;

    int sock = socket(AF_INET, SOCK_STREAM, 0);
    if(sock < 0){
        printf("sock create failed\n");
        return -1;
    }

    Addr = gethostbyname(EMAIL_SERVER);    //用域名获取对应IP
    if(Addr == NULL){
        printf("get ip error\n");
        return -1;
    }
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(25);
    server_addr.sin_addr.S_un.S_addr = (*(struct in_addr*)Addr->h_addr_list[0]).S_un.S_addr;
    ret = connect(sock, (struct sockaddr *)&server_addr, sizeof(server_addr));
    if(ret < 0){
        printf("connect server failed\n");
        return -1;
    }

    return sock;
}

int server_send_recv_display(int sock, char *buff)
{
    int ret = 0;
    char recvbuff[320] = {0};

    send(sock, buff, strlen(buff), 0);
    ret = recv(sock, recvbuff, 320, 0);
    printf("服务器返回消息:len = %d \n recv:[%s] \n",ret,recvbuff);

    return ret;
}


int email_send_helo_fun(int sock)
{
    char buff[320] = {0};
    int ret;

    sprintf(buff, "HELO 126.com\r\n");
    ret = server_send_recv_display(sock, buff);
    if(ret <= 0)
    {
        return -1;
    }

    return 0;
}


int email_send_authlogin_fun(int sock)
{
    char buff[320] = {0};
    int ret;

    sprintf(buff,"%s","AUTH LOGIN\r\n");
    ret = server_send_recv_display(sock, buff);
    if(ret <= 0)
    {
        return -1;
    }

    return 0;
}

//发送用户名
int email_send_username_fun(int sock)
{
    char buff[320] = {0};
    char encbuff[120] = {0};
    int ret, len = 0;

    sprintf(buff, "xxxxxxxxxx@126.com");    //需要改成自己的用户名
    Base64Encod(buff, encbuff, strlen(buff), &len);
    memset(buff, 0x00, sizeof(buff));
    sprintf(buff,"%s\r\n",encbuff);
    ret = server_send_recv_display(sock, buff);
    if(ret <= 0)
    {
        return -1;
    }

    return 0;
}


//发送密码
int email_send_passWord_fun(int sock)
{
    char buff[320] = {0};
    char encbuff[120] = {0};
    int ret, len = 0;

    sprintf(buff, "123456789");          //需要改成自己的密码，有的邮箱是需要填授权码不是登录用的密码
    Base64Encod(buff, encbuff, strlen(buff), &len);
    memset(buff, 0x00, sizeof(buff));
    sprintf(buff, "%s\r\n", encbuff);
    ret = server_send_recv_display(sock, buff);
    if(ret < 0){
        return -1;
    }

    return 0;
}

//发送发件人
int email_send_from_fun(int sock)
{
    char buff[320] = {0};
    int ret;

    sprintf(buff, "MAIL FROM: <xxxxxxxxxx@126.com>\r\n");
    ret = server_send_recv_display(sock, buff);
    if(ret < 0){
        return -1;
    }

    return 0;
}

//发送收件人
int email_send_to_fun(int sock)
{
    char buff[320] = {0};
    int ret;

    sprintf(buff, "RCPT TO: <xxxxxx@163.com>\r\n");
    ret = server_send_recv_display(sock, buff);
    if(ret < 0){
        return -1;
    }

    return 0;
}

//通知服务器准备发送邮件
int email_send_ready_fun(int sock)
{
    char buff[320] = {0};
    int ret;

    sprintf(buff, "DATA\r\n");
    ret = server_send_recv_display(sock, buff);
    if(ret < 0){
        return -1;
    }

    return 0;
}

//发送邮件
int email_send_maintext_fun(int sock)
{
    char buff[320] = {0};
    int ret;

    sprintf(buff, "From: \"pc\"<xxxxxxxxxx@126.com>\r\n"        //发件人
                  "To: \"con\"<xxxxxx@163.com>\r\n"             //收件人
                  "Subject: email test\r\n\r\n"                 //主题
                  "test:\r\n"                                   //正文, 以 \r\n.\r\n 结束
                  "    line1\r\n"
                  "    line2\r\n.\r\n");
    ret = server_send_recv_display(sock, buff);
    if(ret < 0){
        return -1;
    }

    return 0;
}

#define MAX_BUFF_SIZE    512

int main()
{
    int sock;
    char buff[MAX_BUFF_SIZE];
    WSADATA wsa;
    int ret;

    if(WSAStartup(MAKEWORD(1,1), &wsa) != 0){
        printf("WSA startup failed\n");
        return 1;
    }

    sock = CreateSocketAndConnect();
    if(sock < 0){
        return -1;
    }

    printf("connect to server success\n");

    memset(buff, 0x00, sizeof(buff));
    while(1){
        ret = recv(sock, buff, MAX_BUFF_SIZE, 0);
        if(ret < 0){
            printf("recv error\n");
            continue;
        }

        printf("%s", buff);
        break;
    }

    //1.send helo
    if(email_send_helo_fun(sock) < 0){
        return 1;
    }

    //2.send auth login
    if(email_send_authlogin_fun(sock) < 0){
        return 1;
    }

    //3.send username
    if(email_send_username_fun(sock) < 0){
        return 1;
    }

    //4.send password
    if(email_send_password_fun(sock) < 0){
        return 1;
    }

    //5.send from
    if(email_send_from_fun(sock) < 0){
        return 1;
    }

    //6.send to
    if(email_send_to_fun(sock) < 0){
        return 1;
    }

    //7.send notice ready
    if(email_send_ready_fun(sock) < 0){
        return 1;
    }

    //8.send email
    if(email_send_maintext_fun(sock) < 0){
        return 1;
    }

    closesocket(sock);

    return 0;
}