Using a Tunnel to Take Over a Port

An alternative to the SEND / SENDHEX commands is to establish a tunnel between an SCOM port and an external port. In this configuration, all data sent into the SCOM will be output on the external port and all data on the external port will be sent out the SCOM.

Below is a simple example, which sets up an echo on COM2. For a more extensive example of taking over a port, see the intercept.lua script within the sample scripts folder of the development kit.

SocketLib = require("socket")

 

-- Use SCOM1 for commands and logs

local SocketSCOM1 = SocketLib.udp()

-- Use SCOM2 for the tunnel

local SocketSCOM2 = SocketLib.udp()

 

-- Setup the sockets

TargetIP = "127.0.0.1"

 

assert(SocketSCOM1:setsockname("*",0))

assert(SocketSCOM1:setpeername(TargetIP,scom.GetSCOMPort(1)))

assert(SocketSCOM1:settimeout(3))

 

assert(SocketSCOM2:setsockname("*",0))

assert(SocketSCOM2:setpeername(TargetIP,scom.GetSCOMPort(2)))

-- No time out on SCOM2

 

-- Create function to send a command and wait for a prompt

-- Returns the prompt on success, nil on failure

function WaitForPrompt(SocketSCOM_)

  while true do

    local Buffer = SocketSCOM_:receive()

    if Buffer == nil then

      print("Timed out")

      return nil

    end

 

    local Start,Stop,Prompt = Buffer:find("(%[SCOM%d%])")

 

    if Prompt ~= nil then

      print("Prompt Received: ",Prompt)

      return Prompt

    end

  end

 

  return nil

end

 

-- Send a one-byte packet to SCOM2 so that it knows the IP address of the machine

-- running the Lua script

SocketSCOM2:send("\r")

 

-- Setup the tunnel on the SCOM2 side

SocketSCOM1:send("interfacemode scom2 tcom2 none\r")

assert(WaitForPrompt(SocketSCOM1))

 

-- Setup the tunnel on the COM2 side

SocketSCOM1:send("interfacemode com2 tscom2 none\r")

assert(WaitForPrompt(SocketSCOM1))

SocketLib.sleep(1)

 

-- Setup an echo loop

-- This will have the effect that if the user enters characters

-- on COM2, they will be echoed back

while true do

  -- Receive characters from SCOM2

  local Buffer = SocketSCOM2:receive(1)

  print ("Buffer: ",Buffer)

  -- Echo those characters back to SCOM2

  SocketSCOM2:send(Buffer)

end