如何通过socket发送结构？

Question

我找到了以下函数，它可以发送邮件：

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

// 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 false;
}  

// 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 false; 
}  

// 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" );  

// Send RCPT TO: <receiver@domain.com>     
sprintf_s( szMsgLine, "RCPT TO:<%s>%s", to, 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 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", from );
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" ); 

//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" );  

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

WSACleanup();  

return true; 
 } 

我正在进行一个SQL查询，我想通过电子邮件发送结果，但结果可以超过一行。所以我不知道，我怎么能一次发送全部结果。SQL查询的结果将存储在一个结构中(但如果有人有更好的想法，那么我正在听:)。所以我的问题是，是否有一种方法可以在电子邮件中发送这个结构？或者，我如何才能发送作为电子邮件结果的每一行？

谢谢!

Answer 1

在你想要发送你的结构的旁边：

 // All sorts of initializations and stuff
 memcpy(yourbuffer,&yourstructure,sizeof(yourbuffer));

在另一边：

 // Trivial stuff like receiving your buffer :-)
 memcpy(&yourstructure,yourbuffer,sizeof(yourstructure));

Answer 2

要回答您的第一个问题，如果您想通过套接字发送结构，首先必须序列化它。特别是，整数的字节在目标计算机上的顺序可能不同。有许多用于序列化数据的协议，例如ASN.1和JSON。对于C结构，最好使用msgpack或protobufs之类的东西。在序列化数据之后，您就有了一个字节数组，它可以简单地通过套接字发送，一次发送一个块。通常，您还会有一个协议来包装它，它可以像这样简单：

SENDBUF 437\r\n 
GSUOHD*)*IHENHD{@DNJDPOJDPJONK:ND{D@O LDK?ND(G(OBDO*U|GR(G(DIU:OBD

基本上，它是一个命令字符串，后跟这个包中的字节数，然后是回车符、换行符。这是HTTP、memcache和许多其他协议使用的典型协议样式。在换行符之后，您将在输入缓冲区的末尾收集接下来的n个字节(在本例中为437)。由于许多结构可能是多个数据包，因此您可以使用BEGIN和END命令，或者您可以简单地关闭套接字以标记结构的结束。

接收进程将收集字节，直到结构结束，然后反序列化它。

如果您使用像ZeroMQ这样的库，这将简化套接字处理，但您仍然必须处理序列化和反序列化结构。