仿照，SMTP协议初探（一）--我的前一篇博客，结合网上的材料，利用socket，写了个Linux下c编程实现的发邮件程序。

大家可以拿自己的邮箱去做实验啦，base64是一种编码方式，网上可以找到一个网页，可以查询密码的base64编码是多少。当然也可以自己手工计算（我没试过）。

具体源码如下：

//#include<iostream>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
//using namespace std;
#define EHLO "EHLO ***\r\n" //***为邮箱用户名
#define DATA "data\r\n"
#define QUIT "QUIT\r\n" //#define h_addr h_addr_list[0]
//FILE *fin;
int sock;
struct sockaddr_in server;
struct hostent *hp, *gethostbyname();
char buf[BUFSIZ+1];
int len;
char *host_id="smtp.126.com";
char *from_id="***@126.com";
char *to_id="60462****@qq.com";
char *sub="testmail\r\n";
char wkstr[100]="hello how r u\r\n";      /*=====Send a string to the socket=====*/
void send_socket(char *s)
{         write(sock,s,strlen(s));         //write(1,s,strlen(s));         //printf("Client:%s\n",s);
}      //=====Read a string from the socket=====*/
void read_socket()
{len = read(sock,buf,BUFSIZ);write(1,buf,len);//printf("Server:%s\n",buf);
}      /*=====MAIN=====*/
int main(int argc, char* argv[])
{      /*=====Create Socket=====*/sock = socket(AF_INET, SOCK_STREAM, 0);     if (sock==-1)     {perror("opening stream socket");//exit(1);  return 1;   }     else       //cout << "socket created\n";printf("socket created\n");/*=====Verify host=====*/server.sin_family = AF_INET;hp = gethostbyname(host_id);if (hp==(struct hostent *) 0){fprintf(stderr, "%s: unknown host\n", host_id);//exit(2);return 2;}/*=====Connect to port 25 on remote host=====*/memcpy((char *) &server.sin_addr, (char *) hp->h_addr, hp->h_length);                       server.sin_port=htons(25); /* SMTP PORT */if (connect(sock, (struct sockaddr *) &server, sizeof server)==-1){perror("connecting stream socket");//exit(1);return 1;}     else       //cout << "Connected\n";printf("Connected\n");/*=====Write some data then read some =====*/read_socket(); /* SMTP Server logon string */send_socket(EHLO); /* introduce ourselves */read_socket(); /*Read reply *//***added by fupeng*/send_socket("AUTH LOGIN");send_socket("\r\n");read_socket();send_socket("*******");//用户名的base64编码send_socket("\r\n");read_socket();send_socket("******");//密码的base64编码send_socket("\r\n");read_socket();send_socket("mail from <");send_socket(from_id);send_socket(">");send_socket("\r\n");read_socket(); /* Sender OK *///send_socket("VRFY ");//send_socket(from_id);//send_socket("\r\n");     //read_socket(); // Sender OK */send_socket("rcpt to <"); /*Mail to*/send_socket(to_id);send_socket(">");send_socket("\r\n");read_socket(); // Recipient OK*/send_socket(DATA);// body to follow*/read_socket(); //send_socket("from:***@126.com");send_socket("subject:");send_socket(sub);//read_socket(); // Recipient OK*/send_socket("\r\n\r\n");send_socket(wkstr);send_socket(".\r\n");read_socket();send_socket(QUIT); /* quit */read_socket(); // log off *///=====Close socket and finish=====*/close(sock);//exit(0);return 0;
} 

具体结果如下图片所示：