code: protected function prepareConnection()
      {
          // record outgoing headers
          $this->options[CURLINFO_HEADER_OUT] = 1;
  
          if ($this->command->getConnectionTimeout()) {
              $this->options[CURLOPT_TIMEOUT] = $this->command->getConnectionTimeout();
          }
  
          if ($this->node->useTls()) {
              // CA File
              if ($this->node->getCaFile()) {
                  $this->options[CURLOPT_CAINFO] = $this->node->getCaFile();
              } elseif ($this->node->getCaDirectory()) {
                  $this->options[CURLOPT_CAPATH] = $this->node->getCaDirectory();
              } else {
                  throw new Api\Exception('A Certificate Authority file is required for secure connections.');
              }
  
              // verify CA file
              $this->options[CURLOPT_SSL_VERIFYPEER] = true;
  
              // verify host common name
              $this->options[CURLOPT_SSL_VERIFYHOST] = 0;
  
              if ($this->node->getUserName()) {
                  $this->options[CURLOPT_USERPWD] = sprintf('%s:%s', $this->node->getUserName(),
                      $this->node->getPassword());
              } elseif ($this->node->getCertificate()) {
                  /*
                   * NOT CURRENTLY SUPPORTED ON HTTP
                   *
                  $this->options[CURLOPT_SSLCERT] = $this->node->getCertificate();
                  $this->options[CURLOPT_SSLCERTTYPE] = 'P12';
                  if ($this->node->getCertificatePassword()) {
                      $this->options[CURLOPT_SSLCERTPASSWD] = $this->node->getCertificatePassword();
                  }
                  if ($this->node->getPrivateKey()) {
                      $this->options[CURLOPT_SSLKEY] = $this->node->getPrivateKey();
                      if ($this->node->getPrivateKeyPassword()) {
                          $this->options[CURLOPT_SSLKEYPASSWD] = $this->node->getPrivateKeyPassword();
                      }
                  }
                  */
              }
          }
  
          return $this;
      }
docs: Prepare Connection
  
  Sets general connection options that are used with every request
  
  @return $this
  @throws Api\Exception