本文共 6047 字，大约阅读时间需要 20 分钟。

本程序在vs2013测试通过，一共3个文件，发邮件的程序封装为Csmtp 类。

1，测试用的主函数

#include "Csmtp.h"#pragma comment(lib, "Kernel32.lib")  int main(){	Csmtp mail(		25,		"smtp.126.com",		"xxx@126.com",// 来源邮箱		"xxx",   //密码		"xxx.com" //目标邮箱		);	if (!mail.CReateSocket())	{		cout << "ReateSocket failed!" << endl;		return -1;//	}	//标题默认是主机名，内容默认是ip	mail.setTitle("test mail");	mail.setContent("this is content.");	//附件路径错误，不影响邮件正文的发送。	mail.addfile("test.jpg"); //添加附件	//mail.addfile("test2.png"); //添加附件	mail.SendMail(); //类主函数	system("pause");	return 0;}

2， Csmtp类定义

#include 
   
      #include 
    
       #include 
     
      #include 
      
         #include 
       
          //适用平台 Windows#pragma  comment(lib, "ws2_32.lib") /*链接ws2_32.lib动态链接库*/ // POP3服务器（端口：110） Csmtp服务器（端口：25） using namespace std;class Csmtp{	int port;	string domain;	string user;	string pass;	string target;	string title;  //邮件标题	string content;  //邮件内容	HOSTENT* pHostent;	SOCKET sockClient;  //客户端的套接字	vector 
        
          filename; //存储附件名的向量public: Csmtp( int _port, //端口25 string _domain, //域名 string _user, //发送者的邮箱 string _pass, //密码 string _target) //目标邮箱 :port(_port), domain(_domain), user(_user), pass(_pass), target(_target){};//内容 bool CReateSocket(); void setTitle(string tem){ title = tem; } void setContent(string tem){ content = tem; } int SendAttachment(SOCKET &sockClient); int SendMail(); void addfile(string str){ filename.push_back(str); }};
        
       
      
     
    
   

3, Csmtp 类的实现

#include "Csmtp.h"//#include 
   
    //异常类static const char base64Char[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";char* base64Encode(char const* origSigned, unsigned origLength){	unsigned char const* orig = (unsigned char const*)origSigned; // in case any input bytes have the MSB set  	if (orig == NULL) return NULL;	unsigned const numOrig24BitValues = origLength / 3;	bool havePadding = origLength > numOrig24BitValues * 3;	bool havePadding2 = origLength == numOrig24BitValues * 3 + 2;	unsigned const numResultBytes = 4 * (numOrig24BitValues + havePadding);	char* result = new char[numResultBytes + 3]; // allow for trailing '/0'  	// Map each full group of 3 input bytes into 4 output base-64 characters:  	unsigned i;	for (i = 0; i < numOrig24BitValues; ++i)	{		result[4 * i + 0] = base64Char[(orig[3 * i] >> 2) & 0x3F];		result[4 * i + 1] = base64Char[(((orig[3 * i] & 0x3) << 4) | (orig[3 * i + 1] >> 4)) & 0x3F];		result[4 * i + 2] = base64Char[((orig[3 * i + 1] << 2) | (orig[3 * i + 2] >> 6)) & 0x3F];		result[4 * i + 3] = base64Char[orig[3 * i + 2] & 0x3F];	}	// Now, take padding into account.  (Note: i == numOrig24BitValues)  	if (havePadding)	{		result[4 * i + 0] = base64Char[(orig[3 * i] >> 2) & 0x3F];		if (havePadding2)		{			result[4 * i + 1] = base64Char[(((orig[3 * i] & 0x3) << 4) | (orig[3 * i + 1] >> 4)) & 0x3F];			result[4 * i + 2] = base64Char[(orig[3 * i + 1] << 2) & 0x3F];		}		else		{			result[4 * i + 1] = base64Char[((orig[3 * i] & 0x3) << 4) & 0x3F];			result[4 * i + 2] = '=';		}		result[4 * i + 3] = '=';	}	result[numResultBytes] = '\0';	return result;}int Csmtp::SendAttachment(SOCKET &sockClient) /*发送附件*/{	for (std::vector
    
     ::iterator iter = filename.begin(); iter != filename.end(); iter++)	{		cout << "Attachment is sending··· " << endl;		string path = *iter;		ifstream ifs(path, ios::in | ios::binary); //'或链接2个属性，以输入、二进制打开'		if (false == ifs.is_open())		{			cout << "无法打开文件！" << endl;			return 1;		}		string sendstring;		sendstring = "--@boundary@\r\nContent-Type: application/octet-stream; name=\"1.jpg\"\r\n";		sendstring += "Content-Disposition: attachment; filename=\"1.jpg\"\r\n";		sendstring += "Content-Transfer-Encoding: base64\r\n\r\n";		send(sockClient, sendstring.c_str(), sendstring.length(), 0);		//infile.read((char*)buffer,sizeof(数据类型));		// get length of file:		ifs.seekg(0, ifs.end);		int length = ifs.tellg();		ifs.seekg(0, ifs.beg);		cout << "length:" << length << endl;		// allocate memory:		char * buffer = new char[length];		// read data as a block:		ifs.read(buffer, length);		ifs.close();		char *pbase;		pbase = base64Encode(buffer, length);		delete[]buffer;		string str(pbase);		delete[]pbase;		str += "\r\n";		int err = send(sockClient, str.c_str(), strlen(str.c_str()), 0);		if (err != strlen(str.c_str()))		{			cout << "附件发送出错!" << endl;			return 1;		}	}	return 0;}bool Csmtp::CReateSocket(){	WSADATA wsaData;	WORD wVersionRequested = MAKEWORD(2, 1);	//WSAStarup，即WSA(Windows SocKNDs Asynchronous，Windows套接字异步)的启动命令	int err = WSAStartup(wVersionRequested, &wsaData);	cout << "WSAStartup(0:successful):" << err << endl;	char namebuf[128];    //获得本地计算机名	string ip_list;	if (0 == gethostname(namebuf, 128))	{		struct hostent* pHost;  //获得本地IP地址		pHost = gethostbyname(namebuf);  //pHost返回的是指向主机的列表		for (int i = 0; pHost != NULL&&pHost->h_addr_list[i] != NULL; i++)		{			string tem = inet_ntoa(*(struct in_addr *)pHost->h_addr_list[i]);			ip_list += tem;			ip_list += "\n";		}	}	else	{		cout << "获取主机信息失败..." << endl;	}	//	title = namebuf;// 邮件标题	content = ip_list; //主机ip	sockClient = socket(AF_INET, SOCK_STREAM, 0); //建立socket对象  	pHostent = gethostbyname(domain.c_str()); //得到有关于域名的信息	if (pHostent == NULL)	{		printf("创建连接失败，也许没联网！\n");		return false;	}	return true;}int Csmtp::SendMail(){	char *ecode;	char buff[500];  //recv函数返回的结果	int err = 0;	string message; //	SOCKADDR_IN addrServer;  //服务端地址	addrServer.sin_addr.S_un.S_addr = *((DWORD *)pHostent->h_addr_list[0]); //得到smtp服务器的网络字节序的ip地址     	addrServer.sin_family = AF_INET;	addrServer.sin_port = htons(port); //连接端口25 	//int connect (SOCKET s , const struct sockaddr FAR *name , int namelen );	err = connect(sockClient, (SOCKADDR*)&addrServer, sizeof(SOCKADDR));   //向服务器发送请求  	cout << "connect:" << err << endl;	//telnet smtp.126.com 25 连接服务器结束	buff[recv(sockClient, buff, 500, 0)] = '\0';	cout<<"connect:"<
     
      <
      
       \r\nrcpt to:<" + target + ">\r\n";	send(sockClient, message.c_str(), message.length(), 0);	buff[recv(sockClient, buff, 500, 0)] = '\0';	cout<<"mail from: "<
       
        <
       
      
     
    
   

容易理解的简化版可以点击->