如何通過套接字發送結構？

Question

我發現下面的功能，可發送郵件：

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; 
} 

我想提出一個SQL查詢，我想將結果發送到電子郵件，但結果可能是多行。所以我不知道，我怎麼能一次發送整個結果。 SQL查詢的結果將存儲在一個結構中（但如果有人有更好的idee，那麼我在聽:)）。所以我的問題是，如果有一種方法發送這個結構在電子郵件？或者，我怎樣才能發送我在電子郵件中得到的每一行？

謝謝！

Answer 1

在你想給你的結構的一面：

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

在另一側：

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

Answer 2

要回答你的第一個問題，如果你想通過套接字發送結構，首先你必須序列化。特別是，目標機器上的整數字節可能不是相同的順序。有很多序列化數據的協議，例如ASN.1和JSON。對於C結構，你最好使用諸如msgpack或protobufs之類的東西。在序列化數據之後，你有一個字節數組，它可以簡單地通過套接字一次發送一個數據塊。一般情況下，也將具有圍繞纏繞的協議，該協議可以是簡單的：

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

基本上它是一個命令串，隨後的字節在該包，接着回車，換行數目。這是HTTP，memcache和其他許多人使用的典型協議樣式。換行符後，您會在輸入緩衝區的末尾收集下一個n字節（示例中爲437）。由於許多結構將多個數據包，你可能已經BEGIN和END命令，或者你可以簡單地關閉套接字標記一個結構的結束。

接收過程將收集字節，直到該結構的端部，然後反序列化。

如果您使用類似ZeroMQ的庫，這將簡化套接字處理，但您仍然必須處理序列化和反序列化結構。