vl_client.register_capability("ping", 1)

minetest.register_chatcommand("ping", {
	params = "<message>",
	description = "pings the server from the client",
	func = function(param)
		if not vl_client.is_active then
			return false, "Client: not connected to server"
		elseif not vl_client.get_server_capability("ping") then
			return false, "Client: server does not support ping"
		end
        local send_status = vl_client.send_message("ping", {type="request", content=param})
        if not send_status then
			return false, "Client: unable to send ping"
        end
		return true, "Client: pinged server: " .. param
	end,
})

vl_client.register_on_message("ping", function(message)
	if message.type == "request" then
		if type(message.content) ~= "string" then
			minetest.display_chat_message(player_name, "Client: got malformed ping (content)")
			return
		end
		minetest.display_chat_message("Client: got ping: " .. message.content)
		vl_client.send_message("ping", {type="response", content=message.content})
	elseif message.type == "response" then
		if type(message.content) ~= "string" then
			minetest.display_chat_message(player_name, "Client: got malformed ping response (content)")
			return
		end
		minetest.display_chat_message("Client: got response to ping: " .. message.content)
	else
		minetest.display_chat_message("Client: got malformed ping (message)")
	end
end)