static void assertNotSslAlert(final @NotNull DataInputStream in) throws IOException {
    in.mark(1);
    try {
      if (in.read() == 0x15) {
        throw new SSLHandshakeException("Server expecting SSL handshake.");
      }
    } finally {
      in.reset();
    }
  }
If this client is not expecting to use SSL then SSL messages won't be decoded by the SSL layer,
which will result in SSL messages being decoded here. In that even the server side will have
sent us an alert message that we didn't send an SSL message to it.

@param in stream to check for SSL alert message
@throws IOException if stream appears to start with SSL alert message.
geode-tcp-server/src/main/java/org/apache/geode/distributed/internal/tcpserver/TcpClient.java