/**
   * Connects to the remote machine by establishing a tunnel through a HTTP proxy with Basic
   * authentication. It issues a CONNECT request and authenticates with the HTTP proxy with Basic
   * protocol.
   *
   * @param address remote machine to connect to
   * @return a TCP/IP socket connected to the remote machine
   * @throws IOException if an I/O error occurs during handshake (a network problem)
   */
  private Socket authenticateBasic(InetSocketAddress address, ConnectivitySettings cs)
      throws IOException {
    Socket proxy = new Socket(cs.getProxyHost(), cs.getProxyPort());
    BufferedReader r =
        new BufferedReader(
            new InputStreamReader(new InterruptibleInputStream(proxy.getInputStream())));
    DataOutputStream dos = new DataOutputStream(proxy.getOutputStream());

    String username = cs.getProxyUsername() == null ? "" : cs.getProxyUsername();
    String password = cs.getProxyPassword() == null ? "" : String.valueOf(cs.getProxyPassword());
    String credentials = username + ":" + password;
    String basicCookie = Base64Encoder.encode(credentials.getBytes("US-ASCII"));

    dos.writeBytes("CONNECT ");
    dos.writeBytes(address.getHostName() + ":" + address.getPort());
    dos.writeBytes(" HTTP/1.0\r\n");
    dos.writeBytes("Connection: Keep-Alive\r\n");
    dos.writeBytes("Proxy-Authorization: Basic " + basicCookie + "\r\n");
    dos.writeBytes("\r\n");
    dos.flush();

    String line = r.readLine();
    if (sConnectionEstablishedPattern.matcher(line).find()) {
      for (; ; ) {
        line = r.readLine();
        if (line.length() == 0) break;
      }
      return proxy;
    }
    throw new IOException("Basic authentication failed: " + line);
  }