I developed a MFC-Based WinSocket applicatoin,which client part runs in LAN PC and need to across MS ISA Server via HTTP proxy to connect to the Internet Server. Our HTTP proxy port is 8080. I have created Protocol Rule and Site & Content Rule to enable the TCP port for my application. But I got a 502 error in received buffer after I sent 'CONNECT' command.

The total message in buffer is as belowed:
'HTTP/1.1 502 Proxy Error (The specified Secure Sockets Layer(SSL) port is
not allowed. ISA Server' is not configured to allow SSL request from this
port. Most Web browsers use port 443 for SSL requests.) Via:1.1 XXXPROXYSVR
Connection:'.

I looked up this error message in document of ISA Server. But I am not sure
if the error resulted from ISA Server configuration or my application. What
should I do to get rid of this error? Any advice or samples? Thank you.

The Code is:
(lpszAddress and nPort are IP address and TCP port for the Internet Server.)

if( !m_pSocket->Connect(m_strProxyIP,80) )
{
AfxMessageBox(_T("Fails to connect to Proxy Server!"));
m_pSocket->Close();
return FALSE;
}

char buff[600];
sprintf(buff,"%s%s:%d%s","CONNECT ",lpszAddress, nPort,"
HTTP/1.1\r\nUser-Agent:TestApp/0.1\r\n\r\n");
m_pSocket->Send(buff,strlen(buff));
memset(buff,0,600);
m_pSocket->Receive(buff,600);

/*Here, buff gets error message.*/