# File lib/nats/client.rb, line 150
    def connect(uri=nil, opts={}, &blk)
      case uri
      when String
        opts[:uri] = process_uri(uri)
      when Hash
        opts = uri
      end

      # Defaults
      opts[:verbose] = false if opts[:verbose].nil?
      opts[:pedantic] = false if opts[:pedantic].nil?
      opts[:reconnect] = true if opts[:reconnect].nil?
      opts[:ssl] = false if opts[:ssl].nil?
      opts[:max_reconnect_attempts] = MAX_RECONNECT_ATTEMPTS if opts[:max_reconnect_attempts].nil?
      opts[:reconnect_time_wait] = RECONNECT_TIME_WAIT if opts[:reconnect_time_wait].nil?
      opts[:ping_interval] = DEFAULT_PING_INTERVAL if opts[:ping_interval].nil?
      opts[:max_outstanding_pings] = DEFAULT_PING_MAX if opts[:max_outstanding_pings].nil?
      opts[:drain_timeout] = DEFAULT_DRAIN_TIMEOUT if opts[:drain_timeout].nil?

      # Override with ENV
      opts[:uri] ||= ENV['NATS_URI'] || DEFAULT_URI
      opts[:verbose] = ENV['NATS_VERBOSE'].downcase == 'true' unless ENV['NATS_VERBOSE'].nil?
      opts[:pedantic] = ENV['NATS_PEDANTIC'].downcase == 'true' unless ENV['NATS_PEDANTIC'].nil?
      opts[:debug] = ENV['NATS_DEBUG'].downcase == 'true' unless ENV['NATS_DEBUG'].nil?
      opts[:reconnect] = ENV['NATS_RECONNECT'].downcase == 'true' unless ENV['NATS_RECONNECT'].nil?
      opts[:fast_producer_error] = ENV['NATS_FAST_PRODUCER'].downcase == 'true' unless ENV['NATS_FAST_PRODUCER'].nil?
      opts[:ssl] = ENV['NATS_SSL'].downcase == 'true' unless ENV['NATS_SSL'].nil?
      opts[:max_reconnect_attempts] = ENV['NATS_MAX_RECONNECT_ATTEMPTS'].to_i unless ENV['NATS_MAX_RECONNECT_ATTEMPTS'].nil?
      opts[:reconnect_time_wait] = ENV['NATS_RECONNECT_TIME_WAIT'].to_i unless ENV['NATS_RECONNECT_TIME_WAIT'].nil?
      opts[:name] ||= ENV['NATS_CONNECTION_NAME']
      opts[:no_echo] ||= ENV['NATS_NO_ECHO'] || false
      opts[:ping_interval] = ENV['NATS_PING_INTERVAL'].to_i unless ENV['NATS_PING_INTERVAL'].nil?
      opts[:max_outstanding_pings] = ENV['NATS_MAX_OUTSTANDING_PINGS'].to_i unless ENV['NATS_MAX_OUTSTANDING_PINGS'].nil?
      opts[:drain_timeout] ||= ENV['NATS_DRAIN_TIMEOUT'].to_i unless ENV['NATS_DRAIN_TIMEOUT'].nil?

      uri = opts[:uris] || opts[:servers] || opts[:uri]

      if opts[:tls]
        case
        when opts[:tls][:ca_file]
          # Ensure that the file exists before going further
          # in order to report configuration errors during
          # connect synchronously.
          if !File.readable?(opts[:tls][:ca_file])
            raise(Error, "TLS Verification is enabled but ca_file %s is not readable" % opts[:tls][:ca_file])
          end

          # Certificate is supplied so assume we mean verification by default,
          # but still allow disabling explicitly by setting to false.
          opts[:tls][:verify_peer] ||= true
        when (opts[:tls][:verify_peer] && !opts[:tls][:ca_file])
          raise(Error, "TLS Verification is enabled but ca_file is not set")
        else
          # Otherwise, disable verifying peer by default,
          # thus never reaching EM#ssl_verify_peer
          opts[:tls][:verify_peer] = false
        end

        # Allow overriding directly but default to those which server supports.
        opts[:tls][:ssl_version] ||= %w(tlsv1 tlsv1_1 tlsv1_2)
        opts[:tls][:protocols]   ||= %w(tlsv1 tlsv1_1 tlsv1_2)
      end

      # If they pass an array here just pass along to the real connection, and use first as the first attempt..
      # Real connection will do proper walk throughs etc..
      unless uri.nil?
        uris = uri.kind_of?(Array) ? uri : [uri]
        uris.shuffle! unless opts[:dont_randomize_servers]
        u = uris.first
        @uri = u.is_a?(URI) ? u.dup : URI.parse(u)
      end

      @err_cb = proc { |e| raise e } unless err_cb
      @close_cb = proc { } unless close_cb
      @disconnect_cb = proc { } unless disconnect_cb

      client = EM.connect(@uri.host, @uri.port, self, opts)
      client.on_connect(&blk) if blk
      return client
    end