編程環境：WinXP SP2，Visual Studio 2005 Pro

參考資料：《HowTo.SMTP》，《SendMail》(NextFly寫的)，《MSDN 2005》

好了，廢話就不說了。下面是源代碼：

// SendMail.cpp : 定義控制臺應用程序的入口點。
//

＃i nclude "stdafx.h"

＃i nclude <stdio.h>
＃i nclude <stdlib.h>
＃i nclude <winsock2.h>

#pragma comment(lib, "ws2_32.lib")

const char *MailData = "From: \"88250\"<dl88250@126.com>\r\n"
??????"Subject: This is only a test mail! ^^\r\n.\r\n";


int main(int argc, char *argv[])
{
??
??? WSADATA wsaData;
?WORD wVersionRequested = MAKEWORD(2, 2);
??? struct hostent *pHostent = NULL;
??? SOCKET server = INVALID_SOCKET;
??? struct sockaddr_in service;
??? int retConnect = 0;
??? char Buffer[1024] = {0};
????
?if(WSAStartup(wVersionRequested, &wsaData) != 0){
??printf("Error at WSAStartup()\n");
??goto WSACleanup;
??? }
????
??? server = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);??????? //Create a Socket

??? if(server == INVALID_SOCKET){
??printf("Error at socket(): %ld\n", WSAGetLastError());
??????? goto WSACleanup;
??? }
????
??? pHostent = gethostbyname("smtp.126.com");????????????? //Get the Mail Server Name
??? if(pHostent == NULL){
??printf("The Host Name is Invalid...\n");
??????? goto WSACleanup;
??? }
????
??? service.sin_family = AF_INET;
??? memcpy(&service.sin_addr.s_addr, pHostent->h_addr_list[0], pHostent->h_length);
??? service.sin_port = htons(25);
?
??? //Connect to the remote Mail Server
??? retConnect = connect(server, (struct sockaddr*)&service, sizeof(service));
??? if(retConnect == SOCKET_ERROR){
??printf("Failed to connect.\n");
??????? goto WSACleanup;
??? }
????
??? printf("Connect to %s....\n", inet_ntoa(service.sin_addr));
????
??? //Receive Data From the Mail Server
?ZeroMemory(Buffer, sizeof(Buffer));
??? retConnect = recv(server, Buffer, sizeof(Buffer), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Failed to connect.\n");????
??????? goto WSACleanup;?????
??? }else{
??????? printf("%s\n", Buffer);
??? }
????
??? //Send "HELO Server....\r\n" to the Mail Server
??? retConnect = send(server, "HELO Server....\r\n", strlen("HELO Server....\r\n"), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Send HELO to the Mail Failure.\n");
??????? goto WSACleanup;
??? }else{
??? printf("HELO Server....\n");???
??? }??
????
??? //Receive Data From the Mail Server
??? ZeroMemory(Buffer, sizeof(Buffer));
??? retConnect = recv(server, Buffer, sizeof(Buffer), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Failed to connect.\n");????
??????? goto WSACleanup;?????
??? }else{
??????? printf("%s\n", Buffer);
??? }

??? //Send "AUTH LOGIN\r\n" to the Mail Server
??? retConnect = send(server, "AUTH LOGIN\r\n", strlen("AUTH LOGIN\r\n"), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Send \"AUTH LOGIN\" to Mail Failure.\n");
??????? goto WSACleanup;
??? }else{
??printf("AUTH LOGIN\n");???
??? }??????

??? //Receive Data From the Mail Server
??? ZeroMemory(Buffer, sizeof(Buffer));
??? retConnect = recv(server, Buffer, sizeof(Buffer), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Receive Data From Mail Server Failure.\n");????
??????? goto WSACleanup;?????
??? }else{?
??printf("%s\n", Buffer);
??? }
??
??? //Send UserName to the Mail Server. The UserName is Encoded by Base64.
??? retConnect = send(server, "bGJleW9uZDRrb21h==\r\n", strlen("bGJleW9uZDRrb21h==\r\n"), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Send UserName to the Mail Failure.\n");
??????? goto WSACleanup;
??? }else{
??printf("UserName\n");???
??? }??????
????????
??? //Receive Data From the Mail Server
??? ZeroMemory(Buffer, sizeof(Buffer));
??? retConnect = recv(server, Buffer, sizeof(Buffer), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Receive Data From the Mail Server Failure.\n");????
??????? goto WSACleanup;?????
??? }else{
??????? printf("%s\n", Buffer);
??? }

??? //Send Password to the Mail Server The Password is Encoded by Base64.
??? retConnect = send(server, "bGJleW9uZDRrb21h=\r\n", strlen("bGJleW9uZDRrb21h=\r\n"), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Send Password to Mail Failure.\n");
??????? goto WSACleanup;
??? }else{
??printf("Password\n");???
??? }??
????
??? //Receive Data From the Mail Server
??? ZeroMemory(Buffer, sizeof(Buffer));
??? retConnect = recv(server, Buffer, sizeof(Buffer), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Receive Data From the Mail Server Failure.\n");????
??????? goto WSACleanup;?????
??? }else{
??????? printf("%s\n", Buffer);
??? }

??? //Send "Mail From: " File to the Mail Server, sender's Mail Address
??? retConnect = send(server, "MAIL FROM: <lbeyond4koma@126.com>\r\n", strlen("MAIL FROM: <lbeyond4koma@126.com>\r\n"), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Send \"Mail From: \" to Mail Failure.\n");
??????? goto WSACleanup;
??? }else{
??printf("MAIL FROM: <lbeyond4koma@126.com>\n");???
??? }??
????
??? //Receive Data From the Mail Server
??? ZeroMemory(Buffer, sizeof(Buffer));
??? retConnect = recv(server, Buffer, sizeof(Buffer), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Receive Data From Mail Server Failure.\n");????
??????? goto WSACleanup;?????
??? }else{
??Buffer[retConnect] = ' ';
??????? printf("%s\n", Buffer);
??? }

??? //Send "RCPT TO: " File to the Mail Server, receiver 's Mail Address
??? retConnect = send(server, "RCPT TO: <dl88250@gmail.com>\r\n", strlen("RCPT TO: <dl88250@gmail.com>\r\n"), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Send \"RCPT TO: \" to Mail Failure.\n");
??????? goto WSACleanup;
??? }else{
??printf("RCPT TO: <dl88250@gmail.com>\n");???
??? }??
????
??? //Receive Data From the Mail Server
??? ZeroMemory(Buffer, sizeof(Buffer));
??? retConnect = recv(server, Buffer, sizeof(Buffer), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Receive Data From the Mail Server Failure.\n");????
??????? goto WSACleanup;?????
??? }else{
??????? printf("%s\n", Buffer);
??? }

??? //Send "Data" Fiele to the Mail Server, start to Send mail
??? retConnect = send(server, "Data\r\n", strlen("Data\r\n"), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Send \"Data\" Field to Mail Failure...\n");
??????? goto WSACleanup;
??? }else{
??printf("Data\n");???
??? }??

??? //Receive Data From the Mail Server
??? ZeroMemory(Buffer, sizeof(Buffer));
??? retConnect = recv(server, Buffer, sizeof(Buffer), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Receive Data From Mail Server Failure...\n");????
??????? goto WSACleanup;?????
??? }else{
??????? printf("%s\n", Buffer);
??? }

??? //Send Mail data to the the Mail Server
??? retConnect = send(server, MailData, strlen(MailData), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Send Context Of Mail to Mail Failure...\n");
??????? goto WSACleanup;
??? }else{
??printf("%s\n", MailData);
??? }

??? //Receive Data From the Mail Server
??? ZeroMemory(Buffer, sizeof(Buffer));
??? retConnect = recv(server, Buffer, sizeof(Buffer), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Receive Data From Mail Server Failure...\n");????
??????? goto WSACleanup;?????
??? }else{
??????? printf("%s\n", Buffer);
??? }

??? //Send "QUIT" Context to the Mail Server
??? retConnect = send(server, "QUIT\r\n", strlen("QUIT\r\n"), 0);
??? if(retConnect == SOCKET_ERROR){
??printf("Send \"Quit\" to Mail Failure...\n");
??????? goto WSACleanup;
??? }else{
??printf("Quit\n");???
??? }??
???
??? printf("Send Mail Successful!\n");
??????????????
?WSACleanup:{
??if(server != INVALID_SOCKET){
???closesocket(server);
??????? }
??????? WSACleanup();????????
?}
??? system("pause");
?return 0;
}

其中需要注意的是寄件人地址與郵件內容里的郵件地址的關系：

寄件人的地址必須和你用的連接帳號一致。帳號和密碼是使用Base64編碼的（關于什么是Base64編碼請到http://www.ynutx.net/blog/user1/Myth/archives/2006/1682.html下面看看，它的C實現代碼在下面）。。。。

而在郵件內容里的地址只是一個告訴郵件服務器這封信是誰發的。可以和你所使用的發送帳號不一致！也就是說你可以偽造別人的地址進行郵件發送。。。。

哎，不要干什么干事喲^_^!

好了，下面就是Base64編碼與解碼的實現代碼了：

＃i nclude <stdio.h>
＃i nclude <string.h>

char *ch64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

unsigned char *encode(unsigned char *src, int srclen)
{
?int n, buflen, i, j;
?int pading = 0;
?unsigned char *buf;
?static unsigned char *dst;

?buf = src;
?buflen = n = srclen;
?if(n % 3 != 0){? /* pad with '=' by using a temp buffer */
??pading = 1;
??buflen = n + 3 - n % 3;
??buf = malloc(buflen + 1);
??memset(buf, 0, buflen + 1);
??memcpy(buf, src, n);
??for(i=0;i<3-n%3;i++){
???buf[n+i] = '=';
??}
?}
?dst = malloc(buflen * 4 / 3 + 1);
?memset(dst, 0, buflen * 4 / 3 + 1);
?for(i = 0, j = 0; i < buflen; i += 3, j += 4){
??dst[j] = (buf[i] & 0xFC) >> 2;
??dst[j+1] = ((buf[i] & 0x03) << 4) + ((buf[i+1] & 0xF0) >> 4);
??dst[j+2] = ((buf[i+1] & 0x0F) << 2) + ((buf[i+2] & 0xC0) >> 6);
??dst[j+3] = buf[i+2] & 0x3F;
?}
?for(i = 0; i < buflen * 4 / 3; i++){ /* map 6 bit value to base64 ASCII character */
??dst[i] = ch64[dst[i]];
?}
?if(pading){
??free(buf);
?}
?return dst;
}

unsigned char *decode(unsigned char *src)
{
?int n, i, j;
?unsigned char *p;
?static unsigned char *dst;

?n = strlen(src);
?for(i=0;i<n;i++){ /* map base64 ASCII character to 6 bit value */
??p = strchr(ch64, src[i]);
?if(!p){
??break;
?}
?src[i] = p - ch64;
?}
?dst = malloc(n * 3 / 4 + 1);
?memset(dst, 0, n * 3 / 4 + 1);
?for(i = 0, j = 0; i < n; i += 4, j += 3){
??dst[j] = (src[i] << 2) + ((src[i+1] & 0x30) >> 4);
??dst[j+1] = ((src[i+1] & 0x0F) << 4) + ((src[i+2] & 0x3C) >> 2);
??dst[j+2] = ((src[i+2] & 0x03) << 6) + src[i+3];
?}
?return dst;
}

int main()
{
?char *src = "lbeyond4koma";
?unsigned char *dst1;
?unsigned char *dst2;
?unsigned int i;

?dst1 = encode(src, strlen(src)); /* the second parameter must accord with the first one */
?printf("%s\n", dst1);
?dst2 = decode(dst1);
?for(i = 0; i < _msize(dst2); i++){
??printf("%c",dst2[i]);
?}
?free(dst1);
?free(dst2);
?return 0;
}

呵呵，終于完了。有興趣的可以試試哦，發不了的話加我QQ：845765,或者發郵件給我：DL88250@gmail.com?大家一起研究學習一下！