TCP Window Update packet for every byte read on socket

  • Hi,

    I am using socket messaging to read commands in a Karel program. The sender is a Linux PC. The controller is sending a TCP Window Update packet for every byte it reads from the socket, slowing the process considerably. It takes >200ms to read a 51 byte message.

    I've attached a Wireshark screenshot. Packet 45 is the PC sending commands. Packets 47-70 are the Karel program sending progress messages. Packets 71-122 are all TCP Window Update packets, each incrementing the window size by 1 byte. Messages are received intact and the program works correctly. It is just too slow for our application. I know this is an old beast, but Fanuc's TCP stack should be more efficient than this.

    Has anyone else seen this? Is there a workaround? I looked for system variables that might control the TCP window size or flow control, but didn't find any. Do formatting options on the READ statement help?


    R-J31B controller running version 6.4

    M-16iB/20 robot

    Relevant lines from my Karel code:

    MAX_STR_LEN = 128


    cmd = ''

    READ socket(cmd)



  • AD

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