C语言 发送电子邮件

我用C 语言实现了连接126邮件服务器发送邮件,网上有很多例子,我下了,没有一个能运行起来的,这个是用netbean测试,没有问题了,下面是我的代码(要改三处地方:用户名\密码\发送邮件):
#include <stdio.h>
#include <winsock2.h>
#include <stdlib.h>
#include <string.h>

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

// Function prototype
void StreamClient(char *szServer, short nPort, char *szMessage);
// Helper macro for displaying errors
#define PRINTERROR(s) \
fprintf(stderr,"\n%: %d\n", s, WSAGetLastError())



////////////////////////////////////////////////////////////



int main(int argc, char **argv)
{
        char hostname[255];

WORD wVersionRequested = MAKEWORD(2,0);
WSADATA wsaData;
int nRet;
short nPort;

nPort =25;
nRet = WSAStartup(wVersionRequested, &wsaData);

StreamClient("smtp.126.com", nPort, "AUTH LOGIN\r\n");


WSACleanup();
        return 0;
}

////////////////////////////////////////////////////////////

void StreamClient(char *szServer, short nPort, char *szMessage)
{
printf("\nStream Client connecting to server: %s on port: %d",szServer, nPort);

//
// Find the server
//
    LPHOSTENT lpHostEntry;

lpHostEntry = gethostbyname(szServer);
    if (lpHostEntry == NULL)
    {
        PRINTERROR("gethostbyname()");
        return;
    }

//
// Create a TCP/IP stream socket
//
SOCKET theSocket;

theSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (theSocket == INVALID_SOCKET){
PRINTERROR("socket()");
return;
}

//
// Fill in the address structure
//
SOCKADDR_IN saServer;

saServer.sin_family = AF_INET;
saServer.sin_addr = *((LPIN_ADDR)*lpHostEntry->h_addr_list);
saServer.sin_port = htons(nPort);

//
// connect to the server
//
int nRet;

nRet = connect( theSocket, // Socket
(LPSOCKADDR)&saServer, // Server address
sizeof(struct sockaddr));// Length of server address structure
        printf("\n%d1lL=====================================%d\n",nRet,SOCKET_ERROR);
if (nRet == SOCKET_ERROR)
{
PRINTERROR("socket()");
closesocket(theSocket);
return;
}


    char szBuf[256];


// strcpy(szBuf, "From the Client");
        char buf[350]="0";
        char server[250];
        gethostname(server,250);
        strcpy(buf, "HELO ");
      
        strcat(buf, server);
        strcat(buf, " \r\n");
        printf("%s:::%d",buf,strlen(buf));

//
// Wait for a reply
//
        nRet = recv(theSocket,szBuf,sizeof(szBuf)+1,0);  printf("\nData received OVER DATA: %s", szBuf);

        nRet = send(theSocket, buf, strlen(buf), 0);
        nRet = recv(theSocket, szBuf, sizeof(szBuf), 0); printf("\nData received2: %s", szBuf);

        //发送准备登陆信息
         nRet = send(theSocket, "AUTH LOGIN \r\n", sizeof("AUTH LOGIN \r\n"), 0);
         nRet = recv(theSocket, szBuf, sizeof(szBuf), 0); printf("\nData received LOGIN: %s", szBuf);

         //发送用户名和密码,这里的用户名和密码必须用base64进行转码,发送转码以后的字符串
         nRet = send(theSocket,"用户名\r\n", strlen("用户名\r\n"),0);
         nRet = recv(theSocket, szBuf, sizeof(szBuf),0);printf("\nData receivedUSERNAME: %s", szBuf);

         //发送用户密码
         nRet = send(theSocket,"密码\r\n", strlen("密码\r\n"), 0);
         nRet = recv(theSocket, szBuf, sizeof(szBuf),0); printf("\nData receivedUSERPASSWORD: %s", szBuf);

         //发送[发送邮件]的信箱(改成你的邮箱!)
        send(theSocket,"MAIL FROM:<[email protected]>\r\n",sizeof("MAIL FROM:<[email protected]>\r\n"),0);
   nRet = recv(theSocket, szBuf, sizeof(szBuf)+1, 0);printf("\nData received MAILFROM: %s", szBuf);

        //发送[接收邮件]的邮箱
        nRet= send(theSocket,"RCPT TO:<[email protected]> \r\n",sizeof("RCPT TO:<[email protected]> \r\n"),0);
nRet = recv(theSocket, szBuf, sizeof(szBuf)+1, 0);   printf("\nData received TOMAIL: %s", szBuf);
       
        char MailData[1024] =
"From: \"[email protected]\"\r\n"
"To: [email protected]\r\n"
"Subject: IP Address\r\n\r\n"; //主题可以改成别的

       //各诉邮件服务器，准备发送邮件内容
       send(theSocket,"DATA\r\n", strlen("DATA\r\n"),0);
       nRet = recv(theSocket, szBuf, sizeof(szBuf)+1, 0); printf("\nData receivedSEND DATA: %s", szBuf);
       //发送邮件标题
       send(theSocket,MailData, strlen(MailData),0);
       //发送邮件内容
       send(theSocket,"邮件内容来了!\r\n", strlen("邮件内容来了!\r\n"),0);
       //发送邮件结束
       send(theSocket,"\r\n.\r\n", strlen("\r\n.\r\n"),0);
       //接收邮件服务器返回信息
       nRet = recv(theSocket,szBuf,sizeof(szBuf)+1,0);  printf("\nData received OVER DATA: %s", szBuf);



//
// Display the received data
//
//printf("\nData received3: %s", szBuf);


closesocket(theSocket);
return;
}