我正在尝试创建一个应用程序来发送带有附件的电子邮件。邮件发送工作正常，但我无法附加任何内容。我在网上找到了这段代码。有人可以帮我吗，如何附加文件？到目前为止我的代码:

int sendmail( char * smtpserver, char * from, char * to, char * subject, char * msg )
{
int         iProtocolPort        = 0;
char        szSmtpServerName[64] = "";
char        szToAddr[64]         = "";
char        szFromAddr[64]       = "";
char        szBuffer[4096]       = "";
char        szLine[255]          = "";
char        szMsgLine[255]       = "";
SOCKET      hServer;
WSADATA     WSData;
LPHOSTENT   lpHostEntry;
LPSERVENT   lpServEntry;
SOCKADDR_IN SockAddr;

// Load command-line args
lstrcpyA( szSmtpServerName, smtpserver );
lstrcpyA( szToAddr, to );
lstrcpyA( szFromAddr, from );

// Attempt to intialize WinSock (1.1 or later)
if ( WSAStartup( MAKEWORD( VERSION_MAJOR, VERSION_MINOR ), &WSData ) )
{
    printf( "\nCannot find Winsock v%d.%d or later", VERSION_MAJOR, VERSION_MAJOR );
    return 1;
}

// Lookup email server's IP address.
lpHostEntry = gethostbyname( szSmtpServerName );
if ( !lpHostEntry )
{
    printf( "\nCannot find SMTP mail server %s", szSmtpServerName );
    return 1;
}

// Create a TCP/IP socket, no specific protocol
hServer = socket( PF_INET, SOCK_STREAM, 0 );
if ( hServer == INVALID_SOCKET )
{
    printf( "\nCannot open mail server socket!" );
    return 1;
}

// Get the mail service port
lpServEntry = getservbyname( "mail", 0 );

// Use the SMTP default port if no other port is specified
if ( !lpServEntry ) iProtocolPort = htons( IPPORT_SMTP );
else iProtocolPort = lpServEntry->s_port;

// Setup a Socket Address structure
SockAddr.sin_family = AF_INET;
SockAddr.sin_port   = iProtocolPort;
SockAddr.sin_addr   = *( (LPIN_ADDR)*lpHostEntry->h_addr_list );

// Connect the Socket
if ( connect( hServer, ( PSOCKADDR ) &SockAddr, sizeof( SockAddr ) ) )
{
    printf( "\nError connecting to Server socket!" );
    return 1;
}

// Receive initial response from SMTP server
Check( recv( hServer, szBuffer, sizeof( szBuffer ), 0), "recv() Reply" );

// Send HELO server.com
sprintf_s( szMsgLine, "HELO %s%s", smtpserver, CRLF );
Check( send( hServer, szMsgLine, strlen( szMsgLine ), 0 ), "send() HELO" );
Check( recv( hServer, szBuffer, sizeof( szBuffer ), 0 ), "recv() HELO" );

// Send MAIL FROM: <sender@mydomain.com>
sprintf_s( szMsgLine, "MAIL FROM:<%s>%s", from, CRLF );
Check( send( hServer, szMsgLine, strlen( szMsgLine ), 0 ), "send() MAIL FROM" );
Check( recv( hServer, szBuffer, sizeof( szBuffer ), 0 ), "recv() MAIL FROM" );

char buf[ 128 ], str[ 512 ];
char * pch;

memset( str, 0, sizeof( str ) );

strcpy_s( str, to );

pch = strtok( str, "," );//separate email addresses at ','
while (pch != NULL)
{
    memset( buf, 0, sizeof( buf ) );
    //printf("Buf: %s\n",pch);
    strcpy_s( buf, pch );
    pch = strtok (NULL, ",");

    // Send RCPT TO: <receiver@domain.com>
    sprintf_s( szMsgLine, "RCPT TO:<%s>%s", buf, CRLF );
    Check( send( hServer, szMsgLine, strlen( szMsgLine ), 0 ), "send() RCPT TO" );
    Check( recv( hServer, szBuffer, sizeof( szBuffer ), 0 ), "recv() RCPT TO" );
}

// Send DATA
sprintf_s( szMsgLine, "DATA%s", CRLF );
Check( send( hServer, szMsgLine, strlen( szMsgLine ), 0 ), "send() DATA" );
Check( recv( hServer, szBuffer, sizeof( szBuffer ), 0 ), "recv() DATA" );

//Send Cc
sprintf_s( szMsgLine, "Cc: %s%s", "test@domain.com",CRLF );
Check( send( hServer, szMsgLine, strlen( szMsgLine ), 0 ), "send() Cc" );

// Send Subject
sprintf_s( szBuffer, "Subject: %s\n", subject );
Check( send( hServer, szBuffer, strlen( szBuffer ), 0 ), "send() Subject" );

//Send From
sprintf_s( szBuffer, "From: %s\n", "BIOS Update" );
Check( send( hServer, szBuffer, strlen( szBuffer ), 0 ), "send() From" );

//Send To
sprintf_s( szBuffer, "To: %s\n\n", to );
Check( send( hServer, szBuffer, strlen( szBuffer ), 0 ), "send() To" );

//Attach
sprintf_s( szMsgLine, "Attachment: %s%s", "d:\\test.txt",CRLF );   //this doesn't work
Check( send( hServer, szMsgLine, strlen( szMsgLine ), 0 ), "send() Attachment" );

sprintf_s( szMsgLine, "%s%s", msg, CRLF );
Check( send( hServer, szMsgLine, strlen( szMsgLine ), 0 ), "send() message-line" );

// Send blank line and a period
sprintf_s( szMsgLine, "%s.%s", CRLF, CRLF );
Check( send( hServer, szMsgLine, strlen( szMsgLine ), 0 ), "send() end-message" );
Check( recv(  hServer, szBuffer, sizeof( szBuffer ), 0 ), "recv() end-message" );

// Send QUIT
sprintf_s( szMsgLine, "QUIT%s", CRLF );
Check( send( hServer, szMsgLine, strlen( szMsgLine ), 0 ), "send() QUIT" );
Check( recv( hServer, szBuffer, sizeof( szBuffer ), 0 ), "recv() QUIT" );

// Report message has been sent
printf( "\nMail sent!" );

// Close server socket and prepare to exit.
closesocket( hServer );

WSACleanup();

return 0;
}

谢谢!

最佳答案

我建议您阅读一下 SMTP 协议(protocol)。

在过去，内容是 UUENCODED，只需将其嵌入带有 UUENCODE header 的电子邮件正文中就足够了。我以前做过很多这样的事情:)

据我所知，现在一切都使用 MIME。按照 Rup 的链接(查看他的评论)或搜索 Internet 以了解 MIME 的作用。搜索互联网也应该给你两件事:

1. 附件编码后 MIME 的示例，以及附件如何在套接字上发送。
2. 可用于为您进行 MIME 编码的资源(库等)，甚至可以将其插入套接字。

您还可以找到 SMTP 库来处理所有 SMTP 协议(protocol)。

您还需要了解更多有关套接字的知识。您真的期望将 Attachment: %s%s", "d:\\test.txt",CRLF 写入套接字会导致系统打开文件并以某种方式流式传输文件的内容吗？文件到套接字？

代码旁注:

为什么要使用 CRLF？所有其他电子邮件 header 发送 \n 以终止一行。这就是所需的一切。

在电子邮件 header 后发送两个换行符(如对“收件人:” header 所做的那样)表示电子邮件 header 结束。您的“附件:”标题实际上构成了电子邮件正文的第一行。

关于c - 如何通过 SMTP 从 C++ 发送带有附件的电子邮件？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/4507768/