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LICENSE.txt

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+                  GNU LESSER GENERAL PUBLIC LICENSE
+                       Version 2.1, February 1999
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+That's all there is to it!

SConscript

@@ -0,0 +1,21 @@
+from building import *
+
+# get current directory
+cwd     = GetCurrentDir()
+# The set of source files associated with this SConscript file.
+src     = Split("""
+src/smtp_client_data.c
+src/smtp_client.c
+""")
+
+if GetDepend(['SMTP_CLIENT_USING_TLS']):
+    src += Glob('src/smtp_client_tls.c')
+
+if GetDepend(['SMTP_CLIENT_USING_SAMPLE']):
+    src += Glob('example/smtp_client_example.c')
+
+path    = [cwd + '/inc']
+
+group = DefineGroup('smtp_client', src, depend = ['PKG_USING_SMTP_CLIENT'], CPPPATH = path)
+
+Return('group')

example/smtp_client_example.c

@@ -0,0 +1,85 @@
+/*************************************************
+ Copyright (c) 2019
+ All rights reserved.
+ File name:     smtp_client_example.c
+ Description:   smtp发送邮件示例邮件
+ History:
+ 1. Version:    
+    Date:       2019-10-14
+    Author:     wangjunjie
+    Modify:     
+*************************************************/
+#include "smtp_client.h"
+#include "rtthread.h"
+
+//若使用TLS加密则需要更大的堆栈空间
+#ifdef SMTP_CLIENT_USING_TLS
+#define SMTP_CLIENT_THREAD_STACK_SIZE 4096
+#else
+#define SMTP_CLIENT_THREAD_STACK_SIZE 2048
+#endif
+
+/*
+ *邮件信息相关宏定义
+ */
+//smtp 服务器域名
+#define SMTP_SERVER_ADDR "smtp.qq.com"
+//smtp 服务器端口号
+#define SMTP_SERVER_PORT "25"
+//smtp 登录用户名
+#define SMTP_USERNAME    ""
+//smtp 登录密码（或凭证）
+#define SMTP_PASSWORD    ""
+//smtp 邮件发送方（必须为登录用户名）
+#define SMTP_MAIL_FROM   SMTP_USERNAME
+//smtp 邮件接收方
+#define SMTP_RCPT_TO     ""
+//邮件主题
+#define SMTP_SUBJECT     "SMTP TEST"
+
+
+//邮件内容
+char *content = "THIS IS SMTP TEST\r\n"
+                "HELLO SMTP\r\n"
+                "--------------------------------------\r\n"
+                "based on --->   RT-Thread\r\n"
+                "based on ---> SMTP_CLIENT\r\n";
+                
+void smtp_thread(void *param)
+{
+    //手动延时等待网络初始化成功
+    rt_thread_delay(10000);
+
+    //初始化smtp客户端
+    smtp_clinet_init();
+    //设置服务器地址
+    smtp_set_server_addr(SMTP_SERVER_ADDR, ADDRESS_TYPE_DOMAIN, SMTP_SERVER_PORT);
+    //设置服务器认证信息
+    smtp_set_auth(SMTP_USERNAME, SMTP_PASSWORD);
+
+    //发送邮件
+    rt_kprintf("\r\n[smtp]: O > start to send mail\r\n");
+    if (smtp_send_mail(SMTP_MAIL_FROM, SMTP_RCPT_TO, SMTP_SUBJECT, content) == 0)
+    {
+        //发送成功
+        rt_kprintf("\r\n[smtp]: O > send mail success!\r\n");
+    }
+    else
+    {
+        //发送失败
+        rt_kprintf("\r\n[smtp]: X > send mail fail!\r\n");
+    }
+}
+
+int smtp_thread_entry(void)
+{
+    rt_thread_t smtp_client_tid;
+    //创建邮件发送线程（如果选择在主函数中直接调用邮件发送函数，需要注意主函数堆栈大小，必要时调大）
+    smtp_client_tid = rt_thread_create("smtp", smtp_thread, RT_NULL, SMTP_CLIENT_THREAD_STACK_SIZE, 20, 5);
+    if (smtp_client_tid != RT_NULL)
+    {
+        rt_thread_startup(smtp_client_tid);
+    }
+    return RT_EOK;
+}
+INIT_APP_EXPORT(smtp_thread_entry);

inc/smtp_client.h

@@ -0,0 +1,18 @@
+#ifndef __SMTP_H
+#define __SMTP_H
+#include <stdint.h>
+
+//域名类型
+#define ADDRESS_TYPE_DOMAIN 0
+//IP地址类型
+#define ADDRESS_TYPE_IP 1
+
+//smtp服务初始化
+void smtp_clinet_init(void);
+//设置smtp服务器地址和端口
+int smtp_set_server_addr(const char *server_addr, uint8_t addr_type, const char *port);
+//设置smtp服务器的用户名密码
+int smtp_set_auth(const char *username, const char *password);
+//发送邮件
+int smtp_send_mail(char *from, char *to, char *subject, char *body);
+#endif /* __SMTP_H */

inc/smtp_client_data.h

@@ -0,0 +1,8 @@
+#ifndef __SMTP_DATA_H
+#define __SMTP_DATA_H
+
+#include <stdint.h>
+
+uint32_t smtp_base64_encode(char *target, uint32_t target_len, const char *source, uint32_t source_len);
+
+#endif /* __SMTP_DATA_H */

inc/smtp_client_private.h

@@ -0,0 +1,119 @@
+#ifndef __SMTP_PRIVATE_H
+#define __SMTP_PRIVATE_H
+#include <stdint.h>
+#include <rtthread.h>
+
+#ifdef SMTP_CLIENT_ENABLE_DEBUG_LOG
+#define SMTP_LOG rt_kprintf
+#else
+#define SMTP_LOG(...)
+#endif
+
+#ifdef SMTP_CLIENT_USING_TLS
+#include <tls_certificate.h>
+#include <tls_client.h>
+#endif
+
+#define SMTP_MAX_ADDR_LEN 100
+#define SMTP_MAX_AUTH_LEN 50
+#define SMTP_SEND_CMD_MAX_LEN 100
+#define SMTP_SEND_DATA_HEAD_MAX_LENGTH 128
+#define SMTP_SEND_DATA_MAX_LEN 512
+#define SMTP_RESPONSE_MAX_LEN 512
+
+#ifdef SMTP_CLIENT_USING_TLS
+//缓冲区大小
+#define MBEDTLS_READ_BUFFER_LEN 1024
+#endif
+
+//smtp 会话阶段
+enum smtp_session_state
+{
+    SMTP_NULL,
+    SMTP_HELO,
+    SMTP_START_TLS,
+    SMTP_FINISH_START_TLS,
+    SMTP_AUTH_LOGIN,
+    SMTP_MAIL,
+    SMTP_RCPT,
+    SMTP_DATA,
+    SMTP_BODY,
+    SMTP_QUIT,
+    SMTP_CLOSED
+};
+
+//smtp 会话结构
+typedef struct
+{
+    //会话状态
+    enum smtp_session_state state;
+    //会话超时时间，如果时间为0，标志超时，则自动关闭连接
+    uint16_t timer;
+    //smtp服务器域名
+    const char *server_domain;
+    //smtp服务器ip
+    const char *server_ip;
+    //smtp服务器端口号
+    const char *server_port;
+    //用户名
+    char username[SMTP_MAX_AUTH_LEN * 2];
+    //密码(有些邮箱服务器需要的是用户凭据)
+    char password[SMTP_MAX_AUTH_LEN * 2];
+    //邮件源地址
+    char *address_from;
+    //邮件目的地址
+    char *address_to;
+    //邮件主题
+    char *subject;
+    //邮件内容
+    char *body;
+    //smtp连接句柄
+    int conn_fd;
+#ifdef SMTP_CLIENT_USING_TLS
+    //tls会话
+    MbedTLSSession *tls_session;
+#endif
+} smtp_session_t;
+
+extern smtp_session_t smtp_session;
+
+#define SMTP_RESP_220 "220"
+#define SMTP_RESP_235 "235"
+#define SMTP_RESP_250 "250"
+#define SMTP_RESP_334 "334"
+#define SMTP_RESP_354 "354"
+#define SMTP_RESP_LOGIN_UNAME "VXNlcm5hbWU6"
+#define SMTP_RESP_LOGIN_PASS "UGFzc3dvcmQ6"
+
+#define SMTP_CMD_EHLO "EHLO DM11\r\n"
+#define SMTP_CMD_AUTHLOGIN "AUTH LOGIN\r\n"
+#define SMTP_CMD_STARTTLS "STARTTLS\r\n"
+#define SMTP_CMD_MAIL_HEAD "MAIL FROM: <"
+#define SMTP_CMD_MAIL_END ">\r\n"
+#define SMTP_CMD_RCPT_HEAD "RCPT TO: <"
+#define SMTP_CMD_RCPT_END ">\r\n"
+#define SMTP_CMD_DATA "DATA\r\n"
+#define SMTP_CMD_HEADER_1 "From: <"
+#define SMTP_CMD_HEADER_2 ">\r\nTo: <"
+#define SMTP_CMD_HEADER_3 ">\r\nSubject: "
+#define SMTP_CMD_HEADER_4 "\r\n\r\n"
+#define SMTP_CMD_BODY_FINISHED "\r\n.\r\n"
+#define SMTP_CMD_QUIT "QUIT\r\n"
+
+#ifdef SMTP_CLIENT_USING_TLS
+//向SSL/TLS中写入数据
+int smtp_mbedtls_client_write(MbedTLSSession *tls_session, char *buf);
+//从 SSL/TLS 中读取数据
+int smtp_mbedtls_client_read(MbedTLSSession *tls_session, char *buf, size_t len);
+
+//smtp mbedtls 网络连接（用于starttls方式）
+int smtp_connect_server_by_starttls(void);
+//开启starttls
+int smtp_mbedtls_starttls(MbedTLSSession *tls_session);
+//smtp 以tls加密方式连接服务器
+int smtp_connect_server_by_tls(void);
+//smtp 关闭tls连接，释放资源
+int smtp_mbedtls_close_connection(void);
+#endif
+
+#endif /* __SMTP_PRIVATE_H */

readme.md

@@ -0,0 +1,152 @@
+# SMTP_CLIENT
+
+## 简介
+
+这是一个基于RT-Thread的SMTP软件包，其支持普通的25端口，同时也支持465和587这两个加密端口。该软件包的使用非常简单方便，如果是基于RT-Thread操作系统，则无需进行任何移植操作即可使用，且仅需调用几个简单的接口即可实现不同端口的邮件发送功能。
+
+## 特性
+
+- 支持25端口
+- 支持加密功能，支持465,587端口。（有些邮件服务器可能不支持其中的某个端口，用户使用前需了解自己所选用的邮件服务器支持哪个端口的smtp功能）
+- 使用简单，无需了解SMTP协议，设置好一些必要参数后仅需一个接口即可实现邮件发送。
+
+## 软件包使用说明
+
+### 准备工作
+ 
+#### Env 配置说明
+
+首先需要下载 SMTP_CLIENT 软件包，并将软件包加入到项目中。在 BSP 目录下使用 menuconfig 命令打开 Env 配置界面，在 `RT-Thread online packages → IoT - internet of things` 中选择 SMTP_CLIENT 软件包，具体路径如下：
+
+```C
+
+RT-Thread online packages
+    IoT - internet of things  --->
+         [*] smtp_client:smtp client package for rt-thread  --->
+                Version (latest) --->
+            [*] use 465/587 port(encrypted port)
+            [ ] enable debug log information
+                smtp_client Options --->
+                    [*] smtp client example
+
+```
+
+- **Version：** 配置软件版本
+- **use 465/587 port(encrypted port):** 使用加密端口，选中后会将 **mbedtls** 软件包加入编译，同时开启 465和587 两个加密端口的支持。
+- **enable debug log information：** 使能调试打印信息
+- **smtp client example：** 加入示例文件
+
+**注意：加入示例文件后不能直接下载使用，默认示例中缺少SMTP的个人参数，需要用户补全自己的用户名密码及接收方邮箱等信息！**
+
+#### 注意事项
+
+ - 开启加密功能后会占用比较大的RAM空间，请根据自己使用的硬件平台决定是否选用加密。并且适当调大调用发送功能的线程的堆栈大小。（推荐大于4096）
+ - 有些邮件服务器不支持某个加密端口或者默认关闭，使用者需要确认自己选用的邮件服务器所支持的端口，并且确认已经打开邮件服务器的SMTP功能。
+ - 若用户在使用的过程中出现加密有关的错误，请参照 RT-Thread **mbedtls** 软件包的说明文档。
+
+ ### 使用说明
+
+ #### 使用步骤
+
+ 1. 调用 `smtp_clinet_init` 函数初始化 smtp_client 客户端
+ 2. 调用 `smtp_set_server_addr` 函数设置服务器的地址及端口
+ 3. 调用 `smtp_set_auth` 函数设置服务器认证信息
+ 4. 调用 `smtp_send_mail` 函数发送邮件
+
+ #### API详解
+
+ ##### 1、初始化SMTP客户端
+
+ ```C
+
+ void smtp_clinet_init(void);
+ 
+ ```
+
+该函数主要用于初始化 smtp 会话结构。
+
+##### 2、设置SMTP服务器地址及端口
+
+```C
+
+int smtp_set_server_addr(const char *server_addr, uint8_t addr_type, const char *port);
+
+```
+
+|参数|说明|
+|---|---|
+|server_addr|服务器地址|
+|addr_type|地址类型（域名或IP）|
+|port|端口|
+
+|返回值|说明|
+|----|----|
+|0|设置成功|
+|-1|设置失败|
+
+该函数用于设置 smtp 服务器地址及端口，地址类型为域名类型和IP类型，分别对应宏 `ADDRESS_TYPE_DOMAIN` 与 ` ADDRESS_TYPE_IP` .**需要注意的是，由于时间仓促及其需求不是很大，目前仅支持域名连接，但如果有需求，在后续版本中会加入IP连接。当然程序中已预留接口，需求紧的用户可使用接口进行拓展**。
+
+##### 3、设置 smtp 服务器认证信息
+
+```C
+
+int smtp_set_auth(const char *username, const char *password);
+
+```
+
+|参数|说明|
+|---|---|
+|username|服务器用户名|
+|password|认证密码或凭据|
+
+|返回值|说明|
+|----|----|
+|0|设置成功|
+|-1|设置失败|
+
+该函数用于设置 smtp 服务器的认证信息，需要注意有些服务器需要用 **凭据** 而非用户登录邮箱时的密码进行认证，用户在连接服务器时需要确认自己所用服务器的认证方式。
+
+##### 4、发送邮件
+
+```C
+
+int smtp_send_mail(char *from, char *to, char *subject, char *body);
+
+```
+
+|参数|说明|
+|---|---|
+|from|发送者邮箱地址|
+|to|接收者邮箱地址|
+|subject|主题|
+|body|内容|
+
+|返回值|说明|
+|----|----|
+|0|发送成功|
+|-1|发送失败|
+
+该函数为邮件发送函数，在用户设置好服务器的连接参数后，可以直接调用该函数进行邮件的发送。需要注意的是，发送者邮箱地址必须和登录用户名相同。
+
+ #### 宏配置说明
+
+若用户在使用过程中发现默认的配置无法满足自身的使用需求，用户可以进入 `smtp_client_private.h` 文件对相关宏定义参数进行配置：
+
+|宏|说明|
+|---|---|
+|SMTP_MAX_ADDR_LEN|邮箱地址最大长度|
+|SMTP_MAX_AUTH_LEN|认证信息最长度|
+|SMTP_SEND_CMD_MAX_LEN|SMTP指令发送最大长度|
+|SMTP_SEND_DATA_HEAD_MAX_LENGTH|邮件头最大长度|
+|SMTP_SEND_DATA_MAX_LEN|邮件内容最大长度|
+|SMTP_RESPONSE_MAX_LEN|服务器响应数据最大长度|
+
+一般情况下，用户需要根据自己内容的大小对 `SMTP_SEND_DATA_MAX_LEN` 进行配置即可。
+
+## 联系方式&感谢
+
+- 维护: WKJay
+- 主页：https://github.com/WKJay/SMTP_CLIENT
+- email: 1931048074@qq.com
+- 若在使用过程中有任何问题，请与作者取得联系。同时欢迎大家参与到该软件包的开发与维护中来，共同创建一个更加完善、稳定的软件包。
+

src/smtp_client.c

@@ -0,0 +1,734 @@
+/*************************************************
+ Copyright (c) 2019
+ All rights reserved.
+ File name:     smtp_client.c
+ Description:   smtp源文件
+ History:
+ 1. Version:    
+    Date:       2019-10-10
+    Author:     wangjunjie
+    Modify:     
+*************************************************/
+
+#include <stdint.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <dfs_posix.h>
+
+#include "smtp_client_private.h"
+#include "smtp_client_data.h"
+#include "smtp_client.h"
+#include "netdb.h"
+
+smtp_session_t smtp_session;
+
+/**
+ * Name:    smtp_clinet_init
+ * Brief:   初始化smtp客户端
+ * Input:   None
+ * Output:  None
+ */
+void smtp_clinet_init(void)
+{
+    memset(&smtp_session, 0, sizeof(smtp_session_t));
+}
+
+/**
+ * Name:    smtp_close_connection
+ * Brief:   smtp关闭连接，释放资源
+ * Input:   None
+ * Output:  成功0，失败-1
+ */
+static int smtp_close_connection(void)
+{
+    int server_port_num = atoi(smtp_session.server_port);
+    if (server_port_num == 25)
+    {
+        return closesocket(smtp_session.conn_fd);
+    }
+#ifdef SMTP_CLIENT_USING_TLS
+    else if (server_port_num == 465 || server_port_num == 587)
+    {
+        return smtp_mbedtls_close_connection();
+    }
+#endif
+    else
+    {
+        return -1;
+    }
+}
+
+/**
+ * Name:    smtp_set_server_addr
+ * Brief:   设置邮箱服务器域名和端口
+ *          地址最大长度由 SMTP_MAX_ADDR_LEN 定义
+ * Input:
+ *  @server_addr: 服务器地址
+ *  @addr_type:   地址类型  
+ *                ADDR_TYPE_DOMAIN  域名类型
+ *                ADDR_TYPE_IP      IP地址类型
+ *  @port:        服务器端口
+ * Output:        0:设置成功，-1,：设置失败  
+ */
+int smtp_set_server_addr(const char *server_addr, uint8_t addr_type, const char *port)
+{
+    uint16_t addr_len = 0;
+    if (server_addr != NULL)
+    {
+        addr_len = strlen(server_addr);
+    }
+    else
+    {
+        SMTP_LOG("[smtp]: X  server addr is null!\r\n");
+        return -1;
+    }
+
+    if (addr_type == ADDRESS_TYPE_DOMAIN)
+    {
+        smtp_session.server_domain = server_addr;
+    }
+    else
+    {
+        if (addr_len > 15)
+        {
+            SMTP_LOG("[smtp]: X  server addr type error!\r\n");
+            return -1;
+        }
+        else
+        {
+            smtp_session.server_ip = server_addr;
+        }
+    }
+
+    if (strlen(port) <= 0)
+    {
+        SMTP_LOG("[smtp]: X  server port is null!\r\n");
+        return -1;
+    }
+    else
+    {
+        smtp_session.server_port = port;
+    }
+    return 0;
+}
+
+/**
+ * Name:    smtp_set_auth
+ * Brief:   设置连接smtp服务的用户名和密码
+ * Input:
+ *  @username:  用户名
+ *  @password:  密码
+ * Output:  设置成功：0，设置失败：-1
+ */
+int smtp_set_auth(const char *username, const char *password)
+{
+    uint32_t username_len = strlen(username);
+    uint32_t password_len = strlen(password);
+
+    if (!(username_len && password_len))
+    {
+        SMTP_LOG("[smtp]: X  username or password invalid!\r\n");
+        return -1;
+    }
+
+    if (smtp_base64_encode(smtp_session.username, SMTP_MAX_AUTH_LEN * 2, username, username_len) == 0)
+    {
+        SMTP_LOG("[smtp]: X  username encode error!\r\n");
+        return -1;
+    }
+
+    if (smtp_base64_encode(smtp_session.password, SMTP_MAX_AUTH_LEN * 2, password, password_len) == 0)
+    {
+        SMTP_LOG("[smtp]: X  password encode error!\r\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+/**
+ * Name:    smtp_connect_server_by_hostname
+ * Brief:   通过域名连接smtp服务器
+ * Input:   None
+ * Output:  成功0，失败-1
+ */
+static int smtp_connect_server_by_hostname(void)
+{
+    int result = -1;
+    char buf[3];
+    struct addrinfo hints, *addr_list, *cur;
+
+    memset(&hints, 0, sizeof(hints));
+    hints.ai_family = AF_INET;
+    hints.ai_socktype = SOCK_STREAM;
+    hints.ai_protocol = IPPROTO_TCP;
+
+    if (getaddrinfo(smtp_session.server_domain, smtp_session.server_port, &hints, &addr_list) != 0)
+    {
+        SMTP_LOG("[smtp]: X  unknow server domain!\r\n");
+        return -1;
+    }
+
+    for (cur = addr_list; cur != NULL; cur = cur->ai_next)
+    {
+        smtp_session.conn_fd = (int)socket(cur->ai_family, cur->ai_socktype,
+                                           cur->ai_protocol);
+        if (smtp_session.conn_fd < 0)
+        {
+            result = -1;
+            continue;
+        }
+
+        if (connect(smtp_session.conn_fd, cur->ai_addr, (uint32_t)cur->ai_addrlen) == 0)
+        {
+            if (read(smtp_session.conn_fd, buf, 3) < 3)
+            {
+                SMTP_LOG("[smtp]: X  smtp server connect fail\r\n");
+                smtp_close_connection();
+                result = -1;
+                break;
+            }
+            else
+            {
+                if (memcmp(buf, "220", 3) == 0)
+                {
+                    SMTP_LOG("\r\n[smtp]: O  smtp server connect success!\r\n");
+                    SMTP_LOG("[smtp]: O  smtp server domain -> %s!\r\n", smtp_session.server_domain);
+                    result = 0;
+                    break;
+                }
+                else
+                {
+                    SMTP_LOG("[smtp]: X  smtp connection response check fail\r\n");
+                    smtp_close_connection();
+                    result = -1;
+                    break;
+                }
+            }
+        }
+        SMTP_LOG("[smtp]: X  smtp server connect fail\r\n");
+        smtp_close_connection();
+        result = -1;
+    }
+
+    freeaddrinfo(addr_list);
+    return result;
+}
+
+/**
+ * Name:    smtp_connect_server_by_ip
+ * Brief:   通过IP连接smtp服务器
+ * Input:   None
+ * Output:  成功0，失败-1
+ */
+static int smtp_connect_server_by_ip(void)
+{
+    int result = -1;
+
+    SMTP_LOG("[smtp]: X  current version don't support ip connect,please use server domain!\r\n");
+
+    return result;
+}
+
+/**
+ * Name:    smtp_flush
+ * Brief:   清空smtp数据读取区缓存
+ * Input:   None
+ * Output:  缓存中的数据个数，失败返回-1
+ */
+static int smtp_flush(void)
+{
+    int result = -1;
+    int server_port = atoi(smtp_session.server_port);
+    char buf[SMTP_RESPONSE_MAX_LEN];
+
+    while (1)
+    {
+        if (server_port == 25)
+        {
+            result = read(smtp_session.conn_fd, buf, SMTP_RESPONSE_MAX_LEN);
+        }
+#ifdef SMTP_CLIENT_USING_TLS
+        else if (server_port == 465)
+        {
+            result = smtp_mbedtls_client_read(smtp_session.tls_session, buf, SMTP_RESPONSE_MAX_LEN);
+        }
+        else if (server_port == 587)
+        {
+            if (smtp_session.state == SMTP_FINISH_START_TLS)
+            {
+                return 0;
+            }
+            else if (smtp_session.state < SMTP_AUTH_LOGIN)
+            {
+                result = read(smtp_session.conn_fd, buf, SMTP_RESPONSE_MAX_LEN);
+            }
+            else
+            {
+                result = smtp_mbedtls_client_read(smtp_session.tls_session, buf, SMTP_RESPONSE_MAX_LEN);
+            }
+        }
+#endif
+        else
+        {
+            SMTP_LOG("[smtp]: X  smtp flush port invalid \r\n");
+            return -1;
+        }
+
+        if (result <= 0)
+        {
+            SMTP_LOG("[smtp]: X  smtp net connection flush fail\r\n");
+            return -1;
+        }
+        return result;
+    }
+}
+
+/**
+ * Name:    smtp_write
+ * Brief:   根据不同的状态调用对应的write
+ * Input:
+ *  @buf:   要写入的数据
+ * Output:  成功写入的个数，错误返回-1
+ */
+static int smtp_write(char *buf)
+{
+    int server_port_num = atoi(smtp_session.server_port);
+    if (server_port_num == 25)
+    {
+        return write(smtp_session.conn_fd, buf, strlen(buf));
+    }
+#ifdef SMTP_CLIENT_USING_TLS
+    else if (server_port_num == 465)
+    {
+        return smtp_mbedtls_client_write(smtp_session.tls_session, buf);
+    }
+    else if (server_port_num == 587)
+    {
+        if (smtp_session.state < SMTP_FINISH_START_TLS)
+        {
+            return write(smtp_session.conn_fd, buf, strlen(buf));
+        }
+        else
+        {
+            return smtp_mbedtls_client_write(smtp_session.tls_session, buf);
+        }
+    }
+#endif
+    else
+    {
+        return -1;
+    }
+}
+
+/**
+ * Name:    smtp_read
+ * Brief:   根据不同的状态调用对应的read
+ * Input:
+ *  @buf:   读取数据的存储区
+ *  @nbyte: 准备读取数据的长度
+ * Output:  成功读取的个数，错误返回-1
+ */
+static int smtp_read(void *buf, size_t nbyte)
+{
+    int server_port_num = atoi(smtp_session.server_port);
+    if (server_port_num == 25)
+    {
+        return read(smtp_session.conn_fd, buf, nbyte);
+    }
+#ifdef SMTP_CLIENT_USING_TLS
+    else if (server_port_num == 465)
+    {
+        return smtp_mbedtls_client_read(smtp_session.tls_session, buf, nbyte);
+    }
+    else if (server_port_num == 587)
+    {
+        if (smtp_session.state < SMTP_FINISH_START_TLS)
+        {
+            return read(smtp_session.conn_fd, buf, nbyte);
+        }
+        else
+        {
+            return smtp_mbedtls_client_read(smtp_session.tls_session, buf, nbyte);
+        }
+    }
+#endif
+    else
+    {
+        return -1;
+    }
+}
+
+/**
+ * Name:    smtp_connect_server
+ * Brief:   smtp连接服务器
+ * Input:   None
+ * Output:  成功0，失败-1
+ */
+static int smtp_connect_server(void)
+{
+    int server_port_num = atoi(smtp_session.server_port);
+    if (server_port_num == 25)
+    {
+        if (smtp_session.server_ip)
+        {
+            return smtp_connect_server_by_ip();
+        }
+        else if (smtp_session.server_domain)
+        {
+            return smtp_connect_server_by_hostname();
+        }
+        else
+        {
+            SMTP_LOG("[smtp]: X  cannot find ip and domain\r\n");
+            return -1;
+        }
+    }
+#ifdef SMTP_CLIENT_USING_TLS
+    else if (server_port_num == 465)
+    {
+        return smtp_connect_server_by_tls();
+    }
+    else if (server_port_num == 587)
+    {
+        return smtp_connect_server_by_starttls();
+    }
+#endif
+    else
+    {
+        SMTP_LOG("[smtp]: X  invalid port number!\r\n");
+        return -1;
+    }
+}
+
+/**
+ * Name:    smtp_send_data_with_response_check
+ * Brief:   smtp数据发送并校验响应
+ * Input:   
+ *  @buf:   待发送的数据
+ *  @response_code: 正确响应码
+ * Output:  成功0，失败-1
+ */
+static int smtp_send_data_with_response_check(char *buf, char *response_code)
+{
+    char response_code_buf[3];
+    memset(response_code_buf, 0, 3);
+
+    if (smtp_session.conn_fd == 0
+#ifdef SMTP_CLIENT_USING_TLS
+        && smtp_session.tls_session == 0)
+#else
+    )
+#endif
+    {
+        SMTP_LOG("[smtp]: X  cannot find net fd\r\n");
+        return -1;
+    }
+    else
+    {
+        smtp_flush();
+        if (smtp_write(buf) != strlen(buf))
+        {
+            SMTP_LOG("[smtp]: X  smtp send fail\r\n");
+            smtp_close_connection();
+            return -1;
+        }
+        else
+        {
+            if (smtp_read(response_code_buf, 3) < 3)
+            {
+                SMTP_LOG("[smtp]: X  smtp read  response fail\r\n");
+                smtp_close_connection();
+                return -1;
+            }
+            if (memcmp(response_code, response_code_buf, 3) != 0)
+            {
+                SMTP_LOG("[smtp]: X  smtp check  response fail\r\n");
+                smtp_close_connection();
+                return -1;
+            }
+            else
+            {
+                return 0;
+            }
+        }
+    }
+}
+
+/**
+ * Name:    smtp_handshake
+ * Brief:   smtp握手认证
+ * Input:   None
+ * Output:  成功0，失败-1
+ */
+static int smtp_handshake(void)
+{
+    int result = -1;
+    result = smtp_send_data_with_response_check(SMTP_CMD_EHLO, "250");
+    if (result != 0)
+    {
+        SMTP_LOG("[smtp]: X  smtp helo fail\r\n");
+        return -1;
+    }
+
+#ifdef SMTP_CLIENT_USING_TLS
+    //STARTTLS
+    if (atoi(smtp_session.server_port) == 587)
+    {
+        smtp_session.state = SMTP_START_TLS;
+        if (smtp_send_data_with_response_check(SMTP_CMD_STARTTLS, "220") != 0)
+        {
+            SMTP_LOG("[smtp]: X  smtp start tls fail\r\n");
+            smtp_close_connection();
+            return -1;
+        }
+
+        smtp_flush();
+
+        if (smtp_mbedtls_starttls(smtp_session.tls_session) != 0)
+        {
+            SMTP_LOG("[smtp]: X  smtp start tls handshake fail\r\n");
+            return -1;
+        }
+        return 0;
+    }
+#endif
+    return result;
+}
+
+/**
+ * Name:    smtp_auth_login
+ * Brief:   smtp用户登录
+ * Input:   None
+ * Output:  成功0，失败-1
+ */
+static int smtp_auth_login(void)
+{
+    char auth_info_buf[SMTP_MAX_AUTH_LEN * 2 + 2];
+    memset(auth_info_buf, 0, SMTP_MAX_AUTH_LEN * 2 + 2);
+#ifdef SMTP_CLIENT_USING_TLS
+    if (atoi(smtp_session.server_port) == 587)
+    {
+        smtp_session.state = SMTP_FINISH_START_TLS;
+    }
+#endif
+    if (smtp_send_data_with_response_check(SMTP_CMD_AUTHLOGIN, "334") != 0)
+    {
+        SMTP_LOG("[smtp]: X  smtp auth login fail\r\n");
+        smtp_close_connection();
+        return -1;
+    }
+#ifdef SMTP_CLIENT_USING_TLS
+    if (atoi(smtp_session.server_port) == 587)
+    {
+        smtp_session.state = SMTP_AUTH_LOGIN;
+    }
+#endif
+    //发送用户名信息
+    sprintf(auth_info_buf, "%s\r\n", smtp_session.username);
+    if (smtp_send_data_with_response_check(auth_info_buf, "334") != 0)
+    {
+        SMTP_LOG("[smtp]: X  smtp send username fail\r\n");
+        smtp_close_connection();
+        return -1;
+    }
+    //发送密码信息
+    sprintf(auth_info_buf, "%s\r\n", smtp_session.password);
+    if (smtp_send_data_with_response_check(auth_info_buf, "235") != 0)
+    {
+        SMTP_LOG("[smtp]: X  smtp password invalid\r\n");
+        smtp_close_connection();
+        return -1;
+    }
+    return 0;
+}
+
+/**
+ * Name:    smtp_set_sender_receiver
+ * Brief:   smtp设置邮箱的发件人与收件人
+ * Input:   None
+ * Output:  发送成功0，发送失败-1
+ */
+static int smtp_set_sender_receiver(void)
+{
+    uint16_t mail_buf_len = SMTP_MAX_ADDR_LEN + strlen(SMTP_CMD_MAIL_HEAD) + strlen(SMTP_CMD_MAIL_END);
+    uint16_t rcpt_buf_len = SMTP_MAX_ADDR_LEN + strlen(SMTP_CMD_RCPT_HEAD) + strlen(SMTP_CMD_RCPT_END);
+    //使用较大的长度
+    uint16_t buf_len = (mail_buf_len > rcpt_buf_len) ? mail_buf_len : rcpt_buf_len;
+
+    char addr_info_buf[buf_len];
+    memset(addr_info_buf, 0, buf_len);
+
+    sprintf(addr_info_buf, "%s%s%s", SMTP_CMD_MAIL_HEAD, smtp_session.address_from, SMTP_CMD_MAIL_END);
+    if (smtp_send_data_with_response_check(addr_info_buf, "250") != 0)
+    {
+        SMTP_LOG("[smtp]: X  smtp set mail from fail\r\n");
+        smtp_close_connection();
+        return -1;
+    }
+
+    sprintf(addr_info_buf, "%s%s%s", SMTP_CMD_RCPT_HEAD, smtp_session.address_to, SMTP_CMD_RCPT_END);
+    if (smtp_send_data_with_response_check(addr_info_buf, "250") != 0)
+    {
+        SMTP_LOG("[smtp]: X  smtp set rcpt to fail\r\n");
+        smtp_close_connection();
+        return -1;
+    }
+    return 0;
+}
+
+/**
+ * Name:    smtp_send_content
+ * Brief:   smtp发送邮件内容
+ * Input:   None
+ * Output:  发送成功0，发送失败-1
+ */
+static int smtp_send_content(void)
+{
+    char content_buf[SMTP_SEND_DATA_HEAD_MAX_LENGTH + SMTP_SEND_DATA_MAX_LEN];
+    memset(content_buf, 0, SMTP_SEND_DATA_HEAD_MAX_LENGTH + SMTP_SEND_DATA_MAX_LEN);
+
+    if (smtp_send_data_with_response_check(SMTP_CMD_DATA, "354") != 0)
+    {
+        SMTP_LOG("[smtp]: X  smtp send data cmd fail\r\n");
+        smtp_close_connection();
+        return -1;
+    }
+    //拼接内容
+    sprintf(content_buf, "FROM: <%s>\r\nTO: <%s>\r\nSUBJECT:%s\r\n\r\n%s\r\n.\r\n",
+            smtp_session.address_from, smtp_session.address_to, smtp_session.subject, smtp_session.body);
+
+    if (smtp_send_data_with_response_check(content_buf, "250") != 0)
+    {
+        SMTP_LOG("[smtp]: X  smtp send data content fail\r\n");
+        smtp_close_connection();
+        return -1;
+    }
+
+    return 0;
+}
+
+/**
+ * Name:    smtp_quit
+ * Brief:   smtp 结束一次完整的通信
+ * Input:   None
+ * Output:  成功0，失败-1
+ */
+static int smtp_quit(void)
+{
+    if (smtp_send_data_with_response_check(SMTP_CMD_QUIT, "221") != 0)
+    {
+        SMTP_LOG("[smtp]: X  smtp quit fail\r\n");
+        smtp_close_connection();
+        return -1;
+    }
+    SMTP_LOG("[smtp]: O  smtp mail send sussess!\r\n");
+    //关闭连接
+    smtp_close_connection();
+    SMTP_LOG("[smtp]: O  close smtp connection!\r\n");
+    return 0;
+}
+
+/**
+ * Name:    smtp_send
+ * Brief:   真实的发送函数
+ * Input:   
+ *  @port_num:  发送邮件的端口号字符串
+ * Output:  发送成功0，发送失败-1
+ */
+static int smtp_send(void)
+{
+    //连接服务器
+    smtp_session.state = SMTP_NULL;
+    if (smtp_connect_server() != 0)
+    {
+        return -1;
+    }
+    //握手确认
+    smtp_session.state = SMTP_HELO;
+    if (smtp_handshake() != 0)
+    {
+        return -1;
+    }
+    //用户认证
+    smtp_session.state = SMTP_AUTH_LOGIN;
+    if (smtp_auth_login() != 0)
+    {
+        return -1;
+    }
+    //设置发件人与收件人
+    smtp_session.state = SMTP_MAIL;
+    if (smtp_set_sender_receiver() != 0)
+    {
+        return -1;
+    }
+    //发送数据
+    smtp_session.state = SMTP_DATA;
+    if (smtp_send_content() != 0)
+    {
+        return -1;
+    }
+    //结束
+    smtp_session.state = SMTP_QUIT;
+    if (smtp_quit() != 0)
+    {
+        return -1;
+    }
+    return 0;
+}
+
+/**
+ * Name:    smtp_send_mail
+ * Brief:   smtp邮件发送
+ * Input:
+ *  @from:     发送者邮箱
+ *  @to:       接受者邮箱
+ *  @subject:  主题
+ *  @body:     内容
+ * Output:  成功0，失败-1
+ */
+int smtp_send_mail(char *from, char *to, char *subject, char *body)
+{
+    if (strlen(from) > SMTP_MAX_ADDR_LEN)
+    {
+        SMTP_LOG("[smtp]: X  sender address is too long!\r\n");
+        return -1;
+    }
+    else
+    {
+        smtp_session.address_from = from;
+    }
+
+    if (strlen(to) > SMTP_MAX_ADDR_LEN)
+    {
+        SMTP_LOG("[smtp]: X  receiver address is too long!\r\n");
+        return -1;
+    }
+    else
+    {
+        smtp_session.address_to = to;
+    }
+
+    if (subject == NULL)
+    {
+        SMTP_LOG("[smtp]: X subject is null!\r\n");
+        return -1;
+    }
+    else
+    {
+        smtp_session.subject = subject;
+    }
+
+    if (body == NULL)
+    {
+        SMTP_LOG("[smtp]: X body is null!\r\n");
+        return -1;
+    }
+    else
+    {
+        smtp_session.body = body;
+    }
+
+    //调用真实的发送函数
+    return smtp_send();
+}

src/smtp_client_data.c

@@ -0,0 +1,76 @@
+/*************************************************
+ Copyright (c) 2019
+ All rights reserved.
+ File name:     smtp_client_data.c
+ Description:   smtp 数据处理源文件
+ History:
+ 1. Version:    
+    Date:       2019-10-10
+    Author:     wangjunjie
+    Modify:     
+*************************************************/
+
+#include <stdint.h>
+#include "smtp_client_private.h"
+
+const uint8_t smtp_base64_table[] = {
+    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
+    'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
+    'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
+    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h',
+    'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p',
+    'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
+    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+    '+', '/'};
+
+/**
+ * Name:    smtp_base64_encode
+ * Brief:   base64加密
+ * Input:
+ *  @target:加密数据存储位置
+ *  @target_len:存储区的长度
+ *  @source:原始数据
+ *  @source_len：原始数据长度
+ * Output:  加密后数据的长度,出错返回0
+ */
+uint32_t
+smtp_base64_encode(char *target, uint32_t target_len, const char *source, uint32_t source_len)
+{
+    uint32_t i;
+    int8_t j;
+    uint32_t target_idx = 0;
+    uint32_t longer = (3 - (source_len % 3) == 3) ? 0 : (3 - (source_len % 3));
+    uint32_t source_len_b64 = source_len + longer;
+    uint32_t len = (((source_len_b64)*4) / 3);
+    uint8_t x = 5;
+    uint8_t current = 0;
+
+    if (target_len < len)
+    {
+        SMTP_LOG("[smtp]: X  target_len is too short\r\n");
+        return 0;
+    }
+
+    for (i = 0; i < source_len_b64; i++)
+    {
+        uint8_t b = (i < source_len ? source[i] : 0);
+        for (j = 7; j >= 0; j--, x--)
+        {
+            uint8_t shift = ((b & (1 << j)) != 0) ? 1 : 0;
+            current |= shift << x;
+            if (x == 0)
+            {
+                target[target_idx++] = smtp_base64_table[current];
+                x = 6;
+                current = 0;
+            }
+        }
+    }
+
+    for (i = len - longer; i < len; i++)
+    {
+        target[i] = '=';
+    }
+
+    return len;
+}

src/smtp_client_tls.c

@@ -0,0 +1,344 @@
+/*************************************************
+ Copyright (c) 2019
+ All rights reserved.
+ File name:     smtp_client_tls.c
+ Description:   
+ History:
+ 1. Version:    
+    Date:       2019-10-12
+    Author:     wangjunjie
+    Modify:     
+*************************************************/
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <rtthread.h>
+
+#include "smtp_client_private.h"
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include <mbedtls/config.h>
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+/**
+ * Name:    smtp_mbedtls_context_create
+ * Brief:   创建smtp加密环境
+ * Input:
+ *  @smtp_session:  smtp会话
+ * Output:  成功返回tls会话，失败返回NULL并释放tls资源
+ */
+static MbedTLSSession *smtp_mbedtls_context_create(smtp_session_t *smtp_session)
+{
+    MbedTLSSession *tls_session = RT_NULL;
+
+    tls_session = (MbedTLSSession *)tls_malloc(sizeof(MbedTLSSession));
+    if (tls_session == RT_NULL)
+    {
+        SMTP_LOG("[smtp]: X  No memory for MbedTLS session object.\r\n");
+        return NULL;
+    }
+    rt_memset(tls_session, 0x0, sizeof(MbedTLSSession));
+
+    //拷贝服务器地址
+    if (smtp_session->server_ip)
+    {
+        tls_session->host = tls_strdup(smtp_session->server_ip);
+    }
+    else if (smtp_session->server_domain)
+    {
+        tls_session->host = tls_strdup(smtp_session->server_domain);
+    }
+    else
+    {
+        SMTP_LOG("[smtp]: X  cannot find server ip or domain\r\n");
+        tls_free(tls_session);
+        return NULL;
+    }
+    //拷贝服务器端口
+    if (smtp_session->server_port)
+    {
+        tls_session->port = tls_strdup(smtp_session->server_port);
+    }
+    else
+    {
+        SMTP_LOG("[smtp]: X  cannot find server port\r\n");
+        if (tls_session->host)
+        {
+            tls_free(tls_session->host);
+        }
+        tls_free(tls_session);
+        return NULL;
+    }
+    //分配数据接收缓冲区
+    tls_session->buffer_len = MBEDTLS_READ_BUFFER_LEN;
+    tls_session->buffer = tls_malloc(tls_session->buffer_len);
+    memset(tls_session->buffer, 0, MBEDTLS_READ_BUFFER_LEN);
+    if (tls_session->buffer == RT_NULL)
+    {
+        SMTP_LOG("[smtp]: X  no memory for MbedTLS buffer\r\n");
+        if (tls_session->host)
+        {
+            tls_free(tls_session->host);
+        }
+        if (tls_session->port)
+        {
+            tls_free(tls_session->port);
+        }
+        tls_free(tls_session);
+        return NULL;
+    }
+    return tls_session;
+}
+
+/**
+ * Name:    smtp_mbedtls_client_init
+ * Brief:   初始化 TLS 客户端
+ * Input:
+ *  @smtp_session:  smtp会话
+ * Output:  成功返回0，失败返回-1并关闭tls连接
+ */
+static int smtp_mbedtls_client_init(MbedTLSSession *tls_session)
+{
+    //设置随机字符串种子
+    char *pers = "hello_smtp";
+    int result = -1;
+
+    if ((result = mbedtls_client_init(tls_session, (void *)pers, strlen(pers))) != 0)
+    {
+        SMTP_LOG("[smtp]: X  MbedTLSClientInit err return : -0x%x\n", -result);
+        mbedtls_client_close(tls_session);
+        SMTP_LOG("[smtp]: O  MbedTLS connection close\n");
+        return -1;
+    }
+    return result;
+}
+
+/**
+ * Name:    smtp_mbedtls_client_context
+ * Brief:   初始化 SSL/TLS 客户端上下文
+ * Input:
+ *  @smtp_session:  smtp会话
+ * Output:  成功返回0，失败返回-1并关闭tls连接
+ */
+static int smtp_mbedtls_client_context(MbedTLSSession *tls_session)
+{
+    int result = -1;
+    if ((result = mbedtls_client_context(tls_session)) < 0)
+    {
+        SMTP_LOG("[smtp]: X  MbedTLSCLlientContext  err return : -0x%x\n", -result);
+        mbedtls_client_close(tls_session);
+        SMTP_LOG("[smtp]: O  MbedTLS connection close\n");
+        return -1;
+    }
+    return result;
+}
+
+/**
+ * Name:    smtp_mbedtls_client_connect
+ * Brief:   建立 SSL/TLS 连接
+ * Input:
+ *  @smtp_session:  smtp会话
+ * Output:  成功返回0，失败返回-1并关闭tls连接
+ */
+static int smtp_mbedtls_client_connect(MbedTLSSession *tls_session)
+{
+    int result = -1;
+    if ((result = mbedtls_client_connect(tls_session)) != 0)
+    {
+        SMTP_LOG("[smtp]: X  MbedTLSCLlientConnect   err return : -0x%x\n", -result);
+        mbedtls_client_close(tls_session);
+        SMTP_LOG("[smtp]: O  MbedTLS connection close\n");
+        return -1;
+    }
+    return result;
+}
+
+/**
+ * Name:    smtp_mbedtls_client_write
+ * Brief:   向SSL/TLS中写入数据
+ * Input:
+ *  @smtp_session:  smtp会话
+ *  @buf:           写入的字符串
+ * Output:  成功写入的字符个数，失败返回-1或0并关闭tls连接
+ */
+int smtp_mbedtls_client_write(MbedTLSSession *tls_session, char *buf)
+{
+    int result = -1;
+    while ((result = mbedtls_client_write(tls_session, (const unsigned char *)buf, strlen(buf))) <= 0)
+    {
+        if (result != MBEDTLS_ERR_SSL_WANT_READ && result != MBEDTLS_ERR_SSL_WANT_WRITE)
+        {
+            SMTP_LOG("[smtp]: X  mbedtls_ssl_write  err return : -0x%x\n", -result);
+            return -1;
+        }
+    }
+    return result;
+}
+
+/**
+ * Name:    smtp_mbedtls_client_read
+ * Brief:   从 SSL/TLS 中读取数据
+ * Input:
+ *  @smtp_session:  smtp会话
+ * Output:  成功读取的字符个数，失败返回-1并关闭tls连接
+ */
+int smtp_mbedtls_client_read(MbedTLSSession *tls_session, char *buf, size_t len)
+{
+    int result = -1;
+    memset(buf, 0x00, len);
+    result = mbedtls_client_read(tls_session, (unsigned char *)buf, len);
+    if (result < 0)
+    {
+        SMTP_LOG("[smtp]: X  mbedtls_ssl_read returned -0x%x\n", -result);
+    }
+    if (result == 0)
+    {
+        SMTP_LOG("[smtp]: X  connection closed\n");
+    }
+    return result;
+}
+
+/**
+ * Name:    smtp_mbedtls_starttls
+ * Brief:   开启starttls
+ * Input:
+ *  @tls_session:   smtp会话
+ * Output:  成功返回0，失败返回-1并关闭连接
+ */
+int smtp_mbedtls_starttls(MbedTLSSession *tls_session)
+{
+    int result = -1;
+    //设置网络操作接口
+    mbedtls_ssl_set_bio(&tls_session->ssl, &tls_session->server_fd, mbedtls_net_send, mbedtls_net_recv, NULL);
+    //TLS握手
+    while ((result = mbedtls_ssl_handshake(&tls_session->ssl)) != 0)
+    {
+        if (result != MBEDTLS_ERR_SSL_WANT_READ && result != MBEDTLS_ERR_SSL_WANT_WRITE)
+        {
+            SMTP_LOG("[smtp]: X  smtp mbedtls handshake fail\n");
+            mbedtls_client_close(tls_session);
+            SMTP_LOG("[smtp]: O  MbedTLS connection close\n");
+            return -1;
+        }
+    }
+    //证书验证
+    result = mbedtls_ssl_get_verify_result(&tls_session->ssl);
+    if (result != 0)
+    {
+        memset(tls_session->buffer, 0x00, tls_session->buffer_len);
+        mbedtls_x509_crt_verify_info((char *)tls_session->buffer, tls_session->buffer_len, "  ! ", result);
+        SMTP_LOG("[smtp]: X  smtp mbedtls crt verify fail\n");
+        mbedtls_client_close(tls_session);
+        SMTP_LOG("[smtp]: O  MbedTLS connection close\n");
+        return -1;
+    }
+    return result;
+}
+
+/**
+ * Name:    smtp_connect_server_by_tls
+ * Brief:   smtp 以tls加密方式连接服务器
+ * Input:   None
+ * Output:  成功返回0，失败返回-1
+ */
+int smtp_connect_server_by_tls(void)
+{
+    int result = -1;
+    //初始化TLS会话
+    smtp_session.tls_session = smtp_mbedtls_context_create(&smtp_session);
+    if (smtp_session.tls_session == NULL)
+    {
+        return -1;
+    }
+    //初始化TLS/SSL客户端
+    result = smtp_mbedtls_client_init(smtp_session.tls_session);
+    if (result != 0)
+    {
+        return -1;
+    }
+    //初始化 SSL/TLS 客户端上下文
+    result = smtp_mbedtls_client_context(smtp_session.tls_session);
+    if (result != 0)
+    {
+        return -1;
+    }
+    //建立ssl连接
+    result = smtp_mbedtls_client_connect(smtp_session.tls_session);
+    if (result != 0)
+    {
+        return -1;
+    }
+    smtp_session.conn_fd = smtp_session.tls_session->server_fd.fd;
+    return result;
+}
+
+/**
+ * Name:    smtp_connect_server_by_starttls
+ * Brief:   smtp mbedtls 网络连接（用于starttls方式）
+ * Input:   None
+ * Output:  成功返回0，失败返回-1并释放资源
+ */
+int smtp_connect_server_by_starttls(void)
+{
+    int result = -1;
+    //初始化TLS会话
+    smtp_session.tls_session = smtp_mbedtls_context_create(&smtp_session);
+    if (smtp_session.tls_session == NULL)
+    {
+        return -1;
+    }
+    //初始化TLS/SSL客户端
+    result = smtp_mbedtls_client_init(smtp_session.tls_session);
+    if (result != 0)
+    {
+        return -1;
+    }
+    //初始化 SSL/TLS 客户端上下文
+    result = smtp_mbedtls_client_context(smtp_session.tls_session);
+    if (result != 0)
+    {
+        return -1;
+    }
+
+    result = mbedtls_net_connect(&smtp_session.tls_session->server_fd, smtp_session.tls_session->host,
+                                 smtp_session.tls_session->port, MBEDTLS_NET_PROTO_TCP);
+
+    if (result != 0)
+    {
+        SMTP_LOG("[smtp]: X  smtp mbedtls net connect fail\n");
+        mbedtls_client_close(smtp_session.tls_session);
+    }
+    smtp_session.conn_fd = smtp_session.tls_session->server_fd.fd;
+    return result;
+}
+
+/**
+ * Name:    smtp_mbedtls_close_connection
+ * Brief:   smtp 关闭tls连接，释放资源
+ * Input:   None
+ * Output:  成功返回0，失败返回-1
+ */
+int smtp_mbedtls_close_connection(void)
+{
+    int result = -1;
+    if (smtp_session.tls_session)
+    {
+        result = mbedtls_client_close(smtp_session.tls_session);
+        if (result == 0)
+        {
+            smtp_session.tls_session = NULL;
+        }
+        else
+        {
+            SMTP_LOG("[smtp]: X  smtp tls session free fail!\r\n");
+        }
+        return result;
+    }
+    else
+    {
+        return 0;
+    }
+}