The net-proto package provides a way to get protocol information.

This is a wrapper for the getprotobyname, getprotobynumber and the getprotoent C functions.

gem install net-proto

gem cert --add <(curl -Ls https://raw.githubusercontent.com/djberg96/net-proto/main/certs/djberg96_pub.pem)

• ffi 1.0.0 or later.

require 'net/proto' # or 'net-proto'

# Using generic method
Net::Proto.get_protocol(1)      # => 'icmp'
Net::Proto.get_protocol('icmp') # => 1

# Using type specific methods
Net::Proto.getprotobynumber(6)   # => 'tcp'
Net::Proto.getprotobyname('tcp') # => 6

# Iterating over all protocols
Net::Proto.getprotoent do |ent|
  p ent
end

Ruby has a predefined set of constants in socket.c in the general form of IPPROTO_XXX, Y. However, using constants in this fashion can be unreliable because it's easy to define your own protocols (I set 'echo' to 7, for example), or to modify/delete entries in /etc/protocols.

See the 'netproto.rdoc' file under the 'doc' directory for more details. There is also an example under the 'examples' directory.