Linux C语言使用SMTP协议发送邮件（使用25端口）

#Linux C语言使用SMTP协议发送邮件（使用25端口）

本程序使用SMTP协议发送邮件，使用普通的25端口，属于非加密邮件。

经测试，可以使用的邮箱服务器有126，163，sohu，QQ企业邮箱等，在使用的时候，有些邮箱可以直接使用密码登录，有些邮件要使用授权码，这个可以看邮箱说明。

返回值：0代表发送邮件成功，<0发送失败。

注意：大部分云服务器禁用了25端口，会导致连接邮箱服务器失败，不是本程序的问题，这种情况需要使用465端口SSL加密方式发邮件，SSL方式发送邮件后面再写。

代码如下

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 	

struct Base64Date6
{
	unsigned int d4:6;
	unsigned int d3:6;
	unsigned int d2:6;
	unsigned int d1:6;
};

char ConvertToBase64(char uc)
{
	if(uc < 26)	
		return 'A' + uc;	
	if(uc < 52)	
		return 'a' + (uc - 26);	
	if(uc < 62)	
		return '0' + (uc - 52);	
	if(uc == 62)	
		return '+';	
	return '/';
}

void  EncodeBase64(char*dbuf,char*buf128,int len)
{
	struct  Base64Date6*ddd =NULL;
	int i = 0;
	char buf[256] = {0};
	char *tmp = NULL;
	char cc = '\0';
	memset(buf, 0, 256);
	strcpy(buf, buf128);
	for(i = 1; i <= len / 3; i++)
	{
		tmp = buf + (i - 1) * 3;
		cc = tmp[2];
		tmp[2] = tmp[0];
		tmp[0] = cc;
		ddd = (struct Base64Date6*)tmp;
		dbuf[(i - 1) * 4 + 0]=ConvertToBase64((unsigned int)ddd->d1);
		dbuf[(i - 1) * 4 + 1]=ConvertToBase64((unsigned int)ddd->d2);
		dbuf[(i - 1) * 4 + 2]=ConvertToBase64((unsigned int)ddd->d3);
		dbuf[(i - 1) * 4 + 3]=ConvertToBase64((unsigned int)ddd->d4);
	}
	if(len % 3 == 1)
	{
		tmp = buf + (i - 1) * 3;
		cc = tmp[2];
		tmp[2] = tmp[0];
		tmp[0] = cc;
		ddd = (struct Base64Date6*)tmp;
		dbuf[(i - 1) * 4 + 0]=ConvertToBase64((unsigned int)ddd->d1);
		dbuf[(i - 1) * 4 + 1]=ConvertToBase64((unsigned int)ddd->d2);
		dbuf[(i - 1) * 4 + 2]='=';
		dbuf[(i - 1) * 4 + 3]='=';
	}
	if(len % 3 == 2)
	{
		tmp = buf + ( i - 1) * 3;
		cc = tmp[2];
		tmp[2] = tmp[0];
		tmp[0] = cc;
		ddd = (struct Base64Date6*)tmp;
		dbuf[(i - 1) * 4 + 0]=ConvertToBase64((unsigned int)ddd->d1);
		dbuf[(i - 1) * 4 + 1]=ConvertToBase64((unsigned int)ddd->d2);
		dbuf[(i - 1) * 4 + 2]=ConvertToBase64((unsigned int)ddd->d3);
		dbuf[(i - 1) * 4 + 3]='=';
	}
	return;
}

class Socket_RAII{
public:
	Socket_RAII(int sockfd)
	{
		m_sockfd = sockfd;
	}
	~Socket_RAII()
	{
		close(m_sockfd);		
	}
private:
	int m_sockfd;
};

int SendEmail(
	const char *smtp,//邮箱服务器地址：如smtp.exmail.qq.com
	unsigned short port,//邮箱服务器商品：25
	const char *account,//发送方的邮箱帐号
	const char *password,//发送方的邮箱密码或授权码
	const char* email,//目标邮箱
	const char* body,//邮件正文件内容，字符串
	const char* from_name,//邮件发送方的名称
	const char* to_name,//邮件接收方的名称
	const char* subject )//邮件主题
{	
	struct sockaddr_in server_addr;	
	memset(&server_addr, 0, sizeof(server_addr));
	server_addr.sin_family = AF_INET;	
	server_addr.sin_port = htons(port);
	hostent* hptr = gethostbyname(smtp); 
	server_addr.sin_addr = *(struct in_addr*)*hptr->h_addr_list;		
	int sockfd = socket(AF_INET, SOCK_STREAM, 0);	
	int ret = connect(sockfd, (struct sockaddr*)(&server_addr), sizeof(server_addr));
	if(ret == -1)
	{
		printf("%s():connect email server failed:%s(errno:%d)\n", 
				__func__, strerror(errno), errno);
		return -1;
	}	
	Socket_RAII Raii(sockfd); //使用RAII关闭SOCKET连接
	char rbuf[255];	
	memset(rbuf, 0, sizeof(rbuf));
	ret = recv(sockfd, rbuf, sizeof(rbuf), 0);
	if(ret <= 0)	
		return -2;
	if(strncmp(rbuf, "220", 3) != 0)
		return -3;
	
	char sbuf[1500];	
	// EHLO
	int len = snprintf(sbuf, sizeof(sbuf), "EHLO HYL-PC\r\n");
	ret = send(sockfd, sbuf, len, 0);
	if(ret == SOCKET_ERROR)
		return -4;
	memset(rbuf, 0, sizeof(rbuf));
	ret = recv(sockfd, rbuf, sizeof(rbuf), 0);	
	if(ret <= 0)	
		return -5;
	if(strncmp(rbuf, "250", 3) != 0)
		return -6;
		
	// AUTH LOGIN
	len = snprintf(sbuf, sizeof(sbuf), "AUTH LOGIN\r\n");
	ret = send(sockfd, sbuf, len, 0);
	if(ret == SOCKET_ERROR)
		return -7;
	memset(rbuf, 0, sizeof(rbuf));
	ret = recv(sockfd, rbuf, sizeof(rbuf), 0);	
	if(ret <= 0)	
		return -8;
	if(strncmp(rbuf, "334", 3) != 0)
		return -9;
	
	//USER
	len = snprintf(sbuf, sizeof(sbuf), "%s", account);
	char login[128];
	memset(login, 0, sizeof(login));
	EncodeBase64(login, sbuf, len);
	len = snprintf(sbuf, sizeof(sbuf), "%s\r\n", login);
	ret = send(sockfd, sbuf, len, 0);
	if(ret == SOCKET_ERROR)
		return -10;
	memset(rbuf, 0, sizeof(rbuf));
	ret = recv(sockfd, rbuf, sizeof(rbuf), 0);	
	if(ret <= 0)	
		return -11;
	if(strncmp(rbuf, "334", 3) != 0)
		return -12;
		
	//PASSWORD
	len = snprintf(sbuf, sizeof(sbuf), "%s", password);
	//char login[128];
	memset(login, 0, sizeof(login));
	EncodeBase64(login, sbuf, len);
	len = snprintf(sbuf, sizeof(sbuf), "%s\r\n", login);
	ret = send(sockfd, sbuf, len, 0);
	if(ret == SOCKET_ERROR)
		return -13;
	memset(rbuf, 0, sizeof(rbuf));
	ret = recv(sockfd, rbuf, sizeof(rbuf), 0);	
	if(ret <= 0)	
		return -14;
	if(strncmp(rbuf, "235", 3) != 0)
		return -15;
	
	// MAIL FROM
	len = snprintf(sbuf, sizeof(sbuf), "MAIL FROM:<%s>\r\n", account);
	ret = send(sockfd, sbuf, len, 0);
	if(ret == SOCKET_ERROR)
		return -16;
	memset(rbuf, 0, sizeof(rbuf));
	ret = recv(sockfd, rbuf, sizeof(rbuf), 0);	
	if(ret <= 0)	
		return -17;
	if(strncmp(rbuf, "250", 3) != 0)
		return -18;	
	
	// RCPT TO
	len = snprintf(sbuf, sizeof(sbuf), "RCPT TO:<%s>\r\n", email);
	ret = send(sockfd, sbuf, len, 0);
	if(ret == SOCKET_ERROR)
		return -19;
	memset(rbuf, 0, sizeof(rbuf));
	ret = recv(sockfd, rbuf, sizeof(rbuf), 0);	
	if(ret <= 0)	
		return -20;
	if(strncmp(rbuf, "250", 3) != 0)
		return -21;
		
	// DATA 准备开始发送邮件内容
	len = snprintf(sbuf, sizeof(sbuf), "DATA\r\n");
	ret = send(sockfd, sbuf, len, 0);
	if(ret == SOCKET_ERROR)
		return -22;
	memset(rbuf, 0, sizeof(rbuf));
	ret = recv(sockfd, rbuf, sizeof(rbuf), 0);	
	if(ret <= 0)	
		return -23;
	if(strncmp(rbuf, "354", 3) != 0)
		return -24;		
		
	// 发送邮件内容，\r\n.\r\n内容结束标记
	len = snprintf(sbuf, sizeof(sbuf),
			"From: %s<%s>\r\n""To: %s<%s>\r\n""Subject: %s\r\n\r\n""%s\r\n.\r\n",
			from_name, account, to_name, email, subject, body);
	ret = send(sockfd, sbuf, len, 0);
	if(ret == SOCKET_ERROR)
		return -25;
	memset(rbuf, 0, sizeof(rbuf));
	ret = recv(sockfd, rbuf, sizeof(rbuf), 0);	
	if(ret <= 0)	
		return -26;
	if(strncmp(rbuf, "250", 3) != 0)
		return -27;	
		
	// QUIT
	len = snprintf(sbuf, sizeof(sbuf), "QUIT\r\n");
	ret = send(sockfd, sbuf, len, 0);
	if(ret == SOCKET_ERROR)
		return -28;
	memset(rbuf, 0, sizeof(rbuf));
	ret = recv(sockfd, rbuf, sizeof(rbuf), 0);	
	if(ret <= 0)	
		return -29;
	if(strncmp(rbuf, "221", 3) != 0)
		return -30;				
	return 0;
};

int main(int argc, char* argv[])
{	
	int ret = SendEmail("smtp.exmail.qq.com", 25, "account","password",
					"[email protected]", "This is the body", "from name",
					"To name", "This is the subject");	
	if(ret == 0)
		printf("SendEmail success\n");
	else
		printf("SendEmail failed,errno= %d\n",ret);
	return 0;
}