# GL7500 with AT&T and Kore SIM: Only the first connection attempt succeeds

**URL:** <https://forum.sierrawireless.com/t/gl7500-with-at-t-and-kore-sim-only-the-first-connection-attempt-succeeds/24040>\
**Category:** GL Series\
**Created:** [June 18, 2021, 7:11pm UTC](https://forum.sierrawireless.com/t/gl7500-with-at-t-and-kore-sim-only-the-first-connection-attempt-succeeds/24040 "2021-06-18T19:11:53Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![sslobodov](https://avatars.discourse-cdn.com/v4/letter/s/838e76/32.png) [@sslobodov](https://forum.sierrawireless.com/u/sslobodov)\
**Post date:** [June 18, 2021, 7:11pm UTC](https://forum.sierrawireless.com/t/gl7500-with-at-t-and-kore-sim-only-the-first-connection-attempt-succeeds/24040/1 "2021-06-18T19:11:53Z")

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I’ve got the GT7500 modem work reliably with Verizon, Rogers and AT&T, except for the AT&T with a Kore SIM. In that case the first TCP session works, but the second one fails to open, and the only fix is to reset or power-cycle the modem. Am I doing something wrong? Below is the summary of the interaction between the modem and the host.

**==== successful first attempt ====**  
AT+KCNXCFG=1,“GPRS”,“[C1.KOREM2M.COM](http://C1.KOREM2M.COM)” =\> OK  
AT+CGREG? =\> +CGREG: 0,1  
at+KTCPCFG=1,0,"\<IP address\>",\<port\> =\> +KTCPCFG: 1  
AT+KTCPSTART=1 =\> +KCNX\_IND: 1,4,1 +KCNX\_IND: 1,1,0 +KTCP\_IND: 1,1 CONNECT  
  
+++  
ATH =\> OK +KTCP\_DATA: 1,  
AT+KTCPCLOSE=1,1 =\> OK  
AT+KTCPDEL=1 =\> OK

**==== second attempt fails ====**  
at+KTCPCFG=1,0,"\<IP address\>",\<port\> =\> +KTCPCFG: 1  
AT+KTCPSTART=1 =\> +KCNX\_IND: 1,4,1 +KCNX\_IND: 1,1,0 **+KTCP\_NOTIF: 1,5**  
+++  
ATH =\> OK  
AT+KTCPCLOSE=1,1 =\> **ERROR**  
AT+KTCPDEL=1 =\> OK

It looks like, while the PDP context “connected”, the second TCP session opening fails with a generic “TCP Error”. To emphasize, this exact command sequence works fine in all other setups.

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**Author:** ![Donald](https://avatars.discourse-cdn.com/v4/letter/d/ac8455/32.png) [@Donald](https://forum.sierrawireless.com/u/Donald)\
**Post date:** [June 20, 2021, 1:24am UTC](https://forum.sierrawireless.com/t/gl7500-with-at-t-and-kore-sim-only-the-first-connection-attempt-succeeds/24040/2 "2021-06-20T01:24:44Z")

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Hi sslobodov,

Which firmware version are you using? If you are not on the latest firmware, please download the latest one and retry.  
You can get it here [AirPrime HL7588 Firmware](https://source.sierrawireless.com/resources/airprime/software/hl7588-firmware/#sthash.5id9Kh0Q.dpbs)

Please provide the output of below commands:  
==== first attempt ====  
ATI3  
AT+CGDCONT?  
AT+CGREG?  
AT+CEREG?  
AT+CGACT?  
AT+CGPADDR  
AT+KCNXCFG=1,“GPRS”,“[C1.KOREM2M.COM](http://C1.KOREM2M.COM)”  
AT+KTCPCFG=1,0,"", =\> +KTCPCFG: 1  
ATH  
AT+KTCPCLOSE=1,1 =\> OK  
AT+KTCPDEL=1 =\> OK

==== second attempt ====  
AT+CGDCONT?  
AT+CGREG?  
AT+CEREG?  
AT+CGACT?  
AT+CGPADDR  
AT+KCNXCFG=1,“GPRS”,“[C1.KOREM2M.COM](http://C1.KOREM2M.COM)”  
AT+KTCPCFG=1,0,"", =\> +KTCPCFG: 1  
AT+KTCPCFG?  
AT+KTCPSTART=1

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<div class="post-metadata">

**Author:** ![sslobodov](https://avatars.discourse-cdn.com/v4/letter/s/838e76/32.png) [@sslobodov](https://forum.sierrawireless.com/u/sslobodov)\
**Post date:** [June 21, 2021, 11:32pm UTC](https://forum.sierrawireless.com/t/gl7500-with-at-t-and-kore-sim-only-the-first-connection-attempt-succeeds/24040/3 "2021-06-21T23:32:12Z")

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Hi Donald,

Thank you for your reply. Here is the output of the commands requested. Is this the latest firmware, or do we need to update it?

AT+CGDCONT?  
+CGDCONT: 1,“IP”,“[c1.korem2m.com](http://c1.korem2m.com)”,“0.0.0.0”,0,0,0,0,0,0

ATI3  
GL7500.A.2.15.151600.201809201422.x7160\_3

OK

AT+CGREG?  
+CGREG: 0,1

OK

AT+CEREG?  
+CEREG: 0,0

OK

AT+CGACT?  
+CGACT: 1,0

OK

AT+CGPADDR  
ERROR

AT+KCNXCFG=1,“GPRS”,“[C1.KOREM2M.COM](http://C1.KOREM2M.COM)”  
OK

at+KTCPCFG=1,0,“ip-address”,port ← actual IP & port not pasted here.  
+KTCPCFG: 1

OK  
AT+KTCPSTART=1  
+KCNX\_IND: 1,4,1

+KCNX\_IND: 1,1,0

+KTCP\_NOTIF: 1,5

ATH  
OK

AT+KTCPCLOSE=1,1  
ERROR  
AT+KTCPDEL=1  
OK

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<div class="post-metadata">

**Author:** ![Donald](https://avatars.discourse-cdn.com/v4/letter/d/ac8455/32.png) [@Donald](https://forum.sierrawireless.com/u/Donald)\
**Post date:** [June 30, 2021, 10:10am UTC](https://forum.sierrawireless.com/t/gl7500-with-at-t-and-kore-sim-only-the-first-connection-attempt-succeeds/24040/4 "2021-06-30T10:10:13Z")

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Hi sslobodov,

Your steps are OK. That may be the issue of AT&T and KORE SIM.