package require http 2.0

      #
      # NOTE: If the 'tls' package is available, always attempt to use HTTPS;
      #       otherwise, only attempt to use HTTP if explicitly allowed.
      #
      if {[catch {package require tls}] == 0} then {
        ::http::register https 443 ::tls::socket
        ::http::register https 443 [list ::tls::socket -tls1 true]

        if {[string range $uri 0 6] eq "http://"} then {
          set uri [appendArgs https:// [string range $uri 7 end]]
        }
      } elseif {$allowInsecureHttp} then {
        if {[string range $uri 0 7] eq "https://"} then {
          set uri [appendArgs http:// [string range $uri 8 end]]