init, changed a few things for GEIGERnet-Server, added sounds for receiving RDS message

rds.lua

@@ -0,0 +1,64 @@
+function ham_radio.get_rds_messages(frequency, is_receiver_station)
+  local transmitters = ham_radio.find_transmitters(frequency)
+  local rds_messages = {}
+  for position, transmitter in pairs(transmitters) do
+    if transmitter.rds_message ~= "" and transmitter.rds_message ~= nil then
+      for rds_message_line in transmitter.rds_message:gmatch("[^\n]+") do
+        -- construct message
+        local message = table.concat({
+          '[ Radio ] ',
+          rds_message_line,
+        }, "")
+        if is_receiver_station then
+          message = table.concat({
+            '[ Radio ] ',
+            rds_message_line
+          }, "")
+        end
+        table.insert(rds_messages, 1, message)
+      end
+    end
+  end
+  return rds_messages
+end
+
+
+function ham_radio:update_rds(player)
+  local name = player:get_player_name()
+  local item = player:get_wielded_item()
+
+  if item:get_name() ~= "ham_radio:handheld_receiver" then
+    return
+  end
+
+  local meta = item:get_meta()
+  local frequency = meta:get_string("frequency")
+  local rds_disabled = meta:get_string("rds_disabled")
+
+  if frequency == "" then
+    return
+  end
+
+  if rds_disabled == "true" then
+    -- disabled receiving RDS messages
+    ham_radio.player_rds[name] = nil
+    return
+  end
+
+  if ham_radio.player_rds[name] == nil then
+    ham_radio.player_rds[name] = ham_radio.get_rds_messages(frequency)
+  end
+  
+  local message = table.remove(ham_radio.player_rds[name])
+  if message ~= nil then
+    minetest.chat_send_player(player:get_player_name(), minetest.colorize(ham_radio.settings.rds_color, message))
+    
+    -- play radio sound
+    ham_radio.play_rds_sound(player)
+
+    -- when all RDS messages are shown, reload them again
+    if not next(ham_radio.player_rds[name]) then
+      ham_radio.player_rds[name] = ham_radio.get_rds_messages(frequency)
+    end
+  end
+end