Connection timeouts

4 thoughts on “Connection timeouts

  1. Hi,

    I have GE865 modem with fw 10.01.001 and I am periodically opening connection to remote server (cca every minute). This works ok most of the time but sometimes on some devices I have +CME ERROR: 559 – timeout in opening socket.

    My application is doing some retries and from the logs this state when it’s not possible to open socket lasts from 5 minutes to almost an hour. I have asked mobile operator for the logs from that time and I can see that the modem sends initial [SYN] packet to which server responds with [SYN, ACK]. However instead of finishing handshake with ACK, modem retransmitts its [SYN] packet as if it did not receive the [SYN, ACK] from server (this is in wireshark marked as TCP Spurious Retransmission). Also I know that ther server is working OK, because other devices connected to it did not have this problem at that time.

    Is there something I can do with this, maybe some TCP timeouts configuration ?


    Roman Bris

    1. Hi,
      I suppose that you took a Wireshark log on the server side and according to your description, it seems that the [SYN, ACK] is not being received back by the module.
      The timeout of the TCP retransmission is fixed, but even changing the timeout won?t help, if the [SYN, ACK] is not received back.
      The module can retry up to 10 times (according to AT#SCFG setting) and then it will raise an error.
      When the issue happens, can you try to connect to a different server, for example our echo test server:

      If even this connection doesn?t work, can you try to deactivate and reactivate the context with this sequence:
        AT#SGACT?       (wait for 1,0)

      1. Hi, thanks for the reponse.

        actually it was the mobile operator who took the logs (so in the middle between device and server).

        Why connecting to a different server? Sure I can add that but as I said I know for a fact that server was running because other devices did not had problem with it at that time. I will add the context reactivation and see if that helps.

        1. Hi,

          I asked you to test with a different server just for refference.
          Normally any additional information is usefull.

          OK, let’s wait for the context reactivation test results.