#autoload

local expl ports

if ! zstyle -a ":completion${curcontext}:ports" ports ports; then
  (( $+_cache_ports )) ||
      : ${(A)_cache_ports:=${${(M)${${(f)"$(</etc/services)"}:#\#*}#*/tcp}%%[ 	]*}}

  ports=( "$_cache_ports[@]" )
fi

_wanted ports expl port && compadd "$@" "$expl[@]" - "$ports[@]"