RAP Protocol

I have several questions regarding RAP protocol that (I believe) Interlink uses to communicate with ABB Robots:

- I have trouble to cross firewall: I was told that RAP protocol uses several TCP / IP ports to comunicate. What are the TCP/IP port range (is it from 0 to 65535? or is there a shorter range used).

- Is it always the client who initiate the TCP IP connection on each prot (like in FTP when using passiv mode)? Is it always using a service port (like the port 21 in FTP)?

- I would be interested to know how the client tells the server which port to listen to.

- Is the RAP protocl public and can I receive the specifications?





  • RussDRussD United States

    The data exchange that occurs between the robot controller and Interlink is based upon RPC.

    The robot is an RPC server and its portmapper is the entity which determines which TCP ports will be used for a particular RAP conversation.

    This process is handled automatically, i.e. cannot be controlled externally, and results in different ports being selected for every connection.

    The only part that Interlink as the client plays in this process is by contcting the portmapper on port 111.

    You should contact your local ABB representative for more information about the RAP protocol.

    Russell Drown
  • Thanks for this clarification. But for me it is still not clear what are the difference between RPC and RAP. Should I get information on RAP and or RPC?  Is there any available public specification on RPC.

    Also, the issue I am trying to address is to connect on the Robot server. I understand in your answer that:

    - The "service port" is the port 111 (correct?)

    - The "portmapper" will tell me which port to listen to (Correct? but how? What will be the frame / protocol format?)?


  • RussDRussD United States

    SUN-RPC (Remote Procedure Call) is a network communications protocol developed by Sun, Inc. to allow devices of different types to communicate using a standard communications interface. RPC is a very specialized subject area unto itself; the RAP protocol is implemented over top of RPC.

    Port 111 is the "well-known" TCP port that is reserved for RPC communications by convention; it does not have anything to do with a particular piece of hardware, e.g. the service port on the controller. The portmapper in the robot listens on this port for connection requests.

    There are many resources on the Internet related to RPC.

    Have tried configuring your firewall to allow Interlink Module to access ports 111 and 3001? This might be all that is required.

    You might also read this thread for more information:


    Russell Drown
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