wireshark tcp stream split in lua script

TcpStreamAnalyze.lua

-- This script is used to analyze tcp stream from the input
-- libcap file.
-- This scirpt current only works well with tshark
-- Usage:
-- 	tshark -X lua_script:TcpStreamAnalyze.lua -r inputfile -R display_filter

do
   filter = "ip.addr == 192.168.201.53 && ip.addr == 192.168.201.46 && tcp.port == 80"
   local streams_table = {}                 -- table to store all tcp streams

   local tcp_stream_f = Field.new("tcp.stream")
   local tcp_srcport_f = Field.new("tcp.srcport")
   local tcp_dstport_f = Field.new("tcp.dstport")

   local function init_listener()
      local tap = Listener.new("frame", filter)
      
      function tap.reset()
         -- nothing
      end

      function tap.packet(pinfo, tvb, ip)
         local tcp_stream = assert(tonumber(tostring(tcp_stream_f())))
         local index = tcp_stream + 1 -- It is customary in
         -- Lua to start arrays with 1 (and not with 0, as in C)
         local number = pinfo.number
         local start_time = assert(tonumber(tostring(pinfo.rel_ts)))
         local tcp_srcport = assert(tonumber(tostring(tcp_srcport_f())))
         local tcp_dstport = assert(tonumber(tostring(tcp_dstport_f())))

         -- print("packet_number: ", number)
         -- print("tcp_stream ", tcp_stream)
         -- print("start_time ", start_time)
         -- print("tcp_srcport ", tcp_srcport)
         -- print("tcp_dstport ", tcp_dstport)
         
         if streams_table[index] == nil then
            -- the first time
            streams_table[index] = {
               tcp_stream = tcp_stream,
               start_time = start_time,
               stop_time = start_time,
               port1 = tcp_srcport,
               port2 = tcp_dstport,
               time = 0,
               packetcnt = 1
            }
            print(index)
         else
            local stream = assert(streams_table[index])
            -- already have this tcp stream
            if start_time > stream.stop_time then
               stream.stop_time = start_time
            end
            if start_time < stream.start_time then
               stream.start_time = start_time
            end
            stream.time = stream.stop_time - stream.start_time
            stream.packetcnt = stream.packetcnt + 1
         end

      end

      function tap.draw()
         -- wirte the streams table to file
         print("Total tcp stream: " , table.getn(streams_table))
         local file = assert(io.open("tcpstreams.txt", "w"))
         file:write("#index\t")
         file:write("start_time\tstop_time\t")
         file:write("time\t")
         file:write("packetcnt\t")
         file:write("port1\tport2\tstream\n")

         table.foreach(streams_table,
                       function(key, val)
                          file:write(key, "\t")
                          file:write(val.start_time, "\t", val.stop_time, "\t")
                          file:write(val.time, "\t")
                          file:write(val.packetcnt, "\t")
                          file:write(val.port1, "\t", val.port2, "\t")
                          file:write(val.tcp_stream, "\n")
                       end)
         
         -- for key, val in ipairs(streams_table) do
         --    file:write(key, "\t")
         --    file:write(val.start_time, "\t", val.stop_time, "\t")
         --    file:write(val.time, "\t")
         --    file:write(val.packetcnt, "\t")
         --    file:write(val.port1, "\t", val.port2, "\t")
         --    file:write(val.tcp_stream, "\n")
         -- end
         
         file:close()
      end

   end

   init_listener()
end