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 ?
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: AT#SD=1,0,10510,”modules.telit.com”
If even this connection doesn?t work, can you try to deactivate and reactivate the context with this sequence: AT#SGACT=1,0 AT#SGACT? (wait for 1,0) AT#SGACT=1,1
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.
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.
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