11.2. Example of Dissector written in Lua

do
        local p_multi = Proto("multi","MultiProto");

        local vs_protos = {
                [2] = "mtp2",
                [3] = "mtp3",
                [4] = "alcap",
                [5] = "h248",
                [6] = "ranap",
                [7] = "rnsap",
                [8] = "nbap"
        }

        local f_proto = ProtoField.uint8("multi.protocol","Protocol",base.DEC,vs_protos)
        local f_dir = ProtoField.uint8("multi.direction","Direction",base.DEC,{ [1] = "incoming", [0] = "outgoing"})
        local f_text = ProtoField.string("multi.text","Text")

        p_multi.fields = { f_proto, f_dir, f_text }

        local data_dis = Dissector.get("data")

        local protos = {
                [2] = Dissector.get("mtp2"),
                [3] = Dissector.get("mtp3"),
                [4] = Dissector.get("alcap"),
                [5] = Dissector.get("h248"),
                [6] = Dissector.get("ranap"),
                [7] = Dissector.get("rnsap"),
                [8] = Dissector.get("nbap"),
                [9] = Dissector.get("rrc"),
                [10] = DissectorTable.get("sctp.ppi"):get_dissector(3), -- m3ua
                [11] = DissectorTable.get("ip.proto"):get_dissector(132), -- sctp
        }

        function p_multi.dissector(buf,pkt,root)

                local t = root:add(p_multi,buf(0,2))
                t:add(f_proto,buf(0,1))
                t:add(f_dir,buf(1,1))

                local proto_id = buf(0,1):uint()

                local dissector = protos[proto_id]

                if dissector ~= nil then
                        dissector:call(buf(2):tvb(),pkt,root)
                elseif proto_id < 2 then
                        t:add(f_text,buf(2))
                        -- pkt.cols.info:set(buf(2,buf:len() - 3):string())
                else
                        data_dis:call(buf(2):tvb(),pkt,root)
                end

        end

        local wtap_encap_table = DissectorTable.get("wtap_encap")
        local udp_encap_table = DissectorTable.get("udp.port")

        wtap_encap_table:add(wtap.USER15,p_multi)
        wtap_encap_table:add(wtap.USER12,p_multi)
        udp_encap_table:add(7555,p_multi)
end