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EVMK2H: [TI-NDK,TCP Stack] TCP 3way handshake broken!

srt35
Intellectual 640 points

Part Number: EVMK2H

Hello community,

Im working on a project with TI-RTOS and EVMK2H. I created TCP client sockets with using NDK Tcp Stack. I have a question about this stack.

TCP using 3-way handshake(SYN, SYNACK, ACK). SYN packets have to be seq=0, SYNACK packets have to be seq=0 ack=1, ACK packets have to be seq=1 ack=1.

In my case, rarely ACK packets have invalid seq&ack numbers while SYN & SYNACK packets has valid seq&ack. So, connection has never established, because EVMK2H sent SYN packet with(seq=2973524992) TCP Server tries to establish with SYNACK (seq=341319682, ack=2973524993) but NDK-TCP stack replies with ACK(Seq=139587585, Ack=4140089672).

This 3-way handshake is not normal:

--->SYN(seq=A)

<---SYNACK(seq=B, ack=A+1)

--->ACK(C not A+1, D not B+1)

How can i handle this problem? 

Best Regards,

Srt

  • 0
    TI__Guru 65405 points
    The team is notified. They will post their feedback directly here.

    BR
    Tsvetolin Shulev
  • 0 in reply to Cvetolin Shulev-XID
    TI__Guru* 95265 points
    Hi,

    What is the Processor SDK RTOS version and NDK version you used? Which test application (your own code?) you ran for TCP client? K2H EVM is client, who is the TCP server? How frequent you met this issue? Is every time this a fresh start (power cycled)? Or you have TCP connection establishing, closing in an infinite loop test?

    Regards, Eric
  • 0 in reply to lding
    Intellectual 640 points

    Hi,

    Thank you for your responses.

    RTOS is `bios_6_37_03_30`, NDK is `ndk_2_22_02_16`. I created TCP Client Socket and Send TCP Connection Request to TCP Server. TCP Server run on another embedded board. There is no problem in first connection. Problem occurs after that one of TCP side power off and power on(Without FIN packets), so other TCP side not recognize it. 

    I tried another test: EVMK2H(TCP Client) and PC(TCP Server) with `SocketTest'er(https://bit.ly/2s2or3Y). I power up EVMK2H and tried TCP Connection with same port(PC still thought established). This time PC side broke TCP 3way handshake (PC sent wrong SYNACK seq&ack numbers). Is it possible a TCP general problem?

    Best Regards,

    Srt

  • 0 in reply to srt35
    TI__Guru* 95265 points
    Hi,

    Are you able to share your TCP client CCS project so I can build and test with a server?

    Regards, Eric