curl -L -i -vx localhost:50000 "https://www.google.com/"
* About to connect() to proxy localhost port 50000 (#0)
*   Trying ::1... Connection refused
*   Trying 127.0.0.1... connected
* Establish HTTP proxy tunnel to www.google.com:443
> CONNECT www.google.com:443 HTTP/1.1
> Host: www.google.com:443
> User-Agent: curl/7.22.0 (i686-pc-linux-gnu) libcurl/7.22.0 OpenSSL/1.0.1 zlib/1.2.3.4 libidn/1.23 librtmp/2.3
> Proxy-Connection: Keep-Alive
>
< HTTP/1.1 200 Connection Established
HTTP/1.1 200 Connection Established
<

* Proxy replied OK to CONNECT request
* successfully set certificate verify locations:
*   CAfile: none
  CApath: /etc/ssl/certs
* SSLv3, TLS handshake, Client hello (1):
* Unknown SSL protocol error in connection to www.google.com:50000
* Closing connection #0
curl: (35) Unknown SSL protocol error in connection to www.google.com:50000