如何用C写的邮件发送程序？
我的邮件发送程序终于写好了。。。。
编程环境：WinXP SP2，Visual Studio 2005 Pro
参考资料：《HowTo.SMTP》，《SendMail》(NextFly写的)，《MSDN 2005》
好了，废话就不说了。下面是源代码：
// SendMail.cpp : 定义控制台应用程序的入口点。
//＃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与邮件内容里的邮件地址的关系：
寄件人的地址必须和你用的连接帐号一致。帐号和密码是使用Base64编码的（关于什么是Base64编码请到http://www.ynutx.net/blog/user1/Myth/archives/2006/1682.html下面看看，它的C实现代码在下面）。。。。
而在邮件内容里的地址只是一个告诉邮件服务器这封信是谁发的。可以和你所使用的发送帐号不一致！也就是说你可以伪造别人的地址进行邮件发送。。。。
哎，不要干什么干事哟^_^!
好了，下面就是Base64编码与解码的实现代码了：
＃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，终于完了。有兴趣的可以试试哦，发不了的话加我QQ：845765,或者发邮件给我：DL88250@gmail.com大家一起研究学习一下！