This is our old Q&A Site. Please post any new questions and answers at

Hi all,

I'm pretty new about the LUA Dissector. I have a problem with my code. Every time that I expand the treelist all subtrees are expanded automatically. How can I avoid this? Also, I'd like to ask you why the subtrees are displayed in grey color instead of white.

Below you will find my code. Thank you in advance for the help


-- New Protocol and  fields
p_mynewproto  = Proto ("MyProtocol", "Test")

-- Define Header fields
local protoHeader = p_mynewproto.fields
protoHeader.rxId        = ProtoField.uint16('protoHeader.rxId'      , 'Rx ID ' , base.HEX, nil)
protoHeader.txId        = ProtoField.uint16('protoHeader.txId'      , 'Tx ID ' , base.HEX, nil)
protoHeader.timeHour    = ProtoField.uint16('protoHeader.timeHour'  , 'Hour  ' , base.HEX, nil)
protoHeader.timeMinute  = ProtoField.uint16('protoHeader.timeMinute', 'Minute' , base.HEX, nil)
protoHeader.timeSecond  = ProtoField.uint16('protoHeader.timeSecond', 'Second' , base.HEX, nil)

-- mynewproto dissector function
function p_mynewproto.dissector (buf, pkt, root)

   -- Check the packet length
   if buf:len() == 0 then return end
   pkt.cols.protocol =

   -- start from offset 0
   local offset = 0

   -- create subtree for mynewproto
   subtreeA = root:add(p_mynewproto, buf(offset,buf:len())):append_text(" [My Protocol Header]")

   -- Rx ID
   subtreeA:add(protoHeader.rxId , buf(offset,2))

   -- Tx ID
   subtreeA:add(protoHeader.txId , buf(offset+2,2))

   -- Time
   subtreeB = subtreeA:add(p_mynewproto, buf(offset+4,6),"[TIME]")

   -- Time Hour
   subtreeB:add(protoHeader.timeHour , buf(offset+4,2))

   -- Time Minute
   subtreeB:add(protoHeader.timeMinute , buf(offset+6,2))

   -- Time Second
   subtreeB:add(protoHeader.timeSecond , buf(offset+8,2))

-- Initialization function
function p_mynewproto.init()

-- Register a chained dissector for port 11111
local udp_dissector_table = DissectorTable.get("udp.port")
dissector = udp_dissector_table:get_dissector(11111)
udp_dissector_table:add(11111, p_mynewproto)

asked 14 May '15, 15:26

Peter1969's gravatar image

accept rate: 0%

edited 27 Jun '15, 18:57

Hadriel's gravatar image


Guys, I found this old wireshark question:

But I don't understand very well the response. How can I adapt it to my code. Thank you Peter.

(17 May '15, 07:51) Peter1969

In your example code above, the sub-tree you're adding is done with this:

subtreeB = subtreeA:add(p_mynewproto, buf(offset+4,6),"[TIME]")

That tells Wireshark to add a child item to subtreeA (which you created earlier), and the thing you're telling wireshark to add is p_mynewproto. But p_mynewproto represents a Protocol (a Proto object), and it's exactly the same protocol that you added when you created subtreeA earlier - so when you expand the tree in the GUI for subtreeA, Wireshark will automatically expand the tree for subtreeB, because they're the same protocol, and thus the same internal tree-type. Also that's why it's gray and not white - because it's a tree item for a Protocol rather than a ProtoField of a protocol. All protocol tree items are colored gray.

What you should be doing instead is creating another ProtoField for a "Time" field - this won't be a distinct field like the others, but rather just something to hold/contain/encapsulate the other time fields. For example by going this:

-- this is with your other ProtoField definitions:
protoHeader.time = ProtoField.bytes('protoHeader.time', 'Time')
-- this is inside your dissector:
subtreeB = subtreeA:add(protoHeader.time, buf(offset+4,6))
-- or this if you don't want to see the bytes shown:
subtreeB = subtreeA:add(protoHeader.time, buf(offset+4,6)):set_text('Time')
permanent link

answered 27 Jun '15, 19:20

Hadriel's gravatar image

accept rate: 18%

Thank you Hadriel, I really appreciate your help.



(29 Jun '15, 08:11) Peter1969

If an answer has solved your issue, please accept the answer for the benefit of other users by clicking the checkmark icon next to the answer. Please read the FAQ for more information.

(29 Jun '15, 08:47) grahamb ♦
Your answer
toggle preview

Follow this question

By Email:

Once you sign in you will be able to subscribe for any updates here



Answers and Comments

Markdown Basics

  • *italic* or _italic_
  • **bold** or __bold__
  • link:[text]( "title")
  • image?![alt text](/path/img.jpg "title")
  • numbered list: 1. Foo 2. Bar
  • to add a line break simply add two spaces to where you would like the new line to be.
  • basic HTML tags are also supported

Question tags:


question asked: 14 May '15, 15:26

question was seen: 2,924 times

last updated: 29 Jun '15, 08:47

p​o​w​e​r​e​d by O​S​Q​A