# KTCP\_DATA limit on HL7800? **URL:** \ **Category:** HL78\ **Created:** [May 2, 2023, 6:18am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667 "2023-05-02T06:18:45Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![hkiol](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/hkiol/32/5998_2.png) [@hkiol](https://forum.sierrawireless.com/u/hkiol)\ **Post date:** [May 2, 2023, 6:18am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/1 "2023-05-02T06:18:45Z")
Hi, There seems to be a limit when I try to send data over TCP to an HL7800 modem. After sending a certain amount of bytes, the +KTCP\_DATA urc always returns `+KTCP_DATA: 1,1629` and the EOF pattern is printed prematurely, so there is a limit. The number 1629 is not always consistent either, as I sometimes get less than that. Trough Wireshark I can see that the right amount of bytes is being sent. data\_mode is not supported so the 1500 byte limit should not be there. Any ideas? thanks ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 2, 2023, 6:34am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/2 "2023-05-02T06:34:55Z")
do you find problem in +KTCPSTART? ---
**Author:** ![hkiol](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/hkiol/32/5998_2.png) [@hkiol](https://forum.sierrawireless.com/u/hkiol)\ **Post date:** [May 2, 2023, 6:43am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/3 "2023-05-02T06:43:13Z")
The problem occurs when sending data to the device while the TCP connection is already established. It’s established with AT+KTCPCNX ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 2, 2023, 6:45am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/4 "2023-05-02T06:45:22Z")
you can still use +KTCPSTART ---
**Author:** ![hkiol](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/hkiol/32/5998_2.png) [@hkiol](https://forum.sierrawireless.com/u/hkiol)\ **Post date:** [May 2, 2023, 6:47am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/5 "2023-05-02T06:47:15Z")
So there is a bug somewhere? Is that bug known? I can’t just change the command into production. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 2, 2023, 6:49am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/6 "2023-05-02T06:49:18Z")
if no problem is found in +KTCPSTART, may need to investigate if this is server problem ---
**Author:** ![hkiol](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/hkiol/32/5998_2.png) [@hkiol](https://forum.sierrawireless.com/u/hkiol)\ **Post date:** [May 2, 2023, 6:53am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/7 "2023-05-02T06:53:48Z")
The server transmits correctly, as I noted wireshark shows the correct amount of bytes sent. Does using KTCPSTART make any difference? Why would that be? Does KTCPSTART return the same replies as TCPCNX does? ![image](https://us1.discourse-cdn.com/flex025/uploads/sierrawireless/original/2X/8/8e81fa7d822de0cb1dfe9e78acd1b52005fae8b6.png) ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 2, 2023, 6:56am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/8 "2023-05-02T06:56:13Z")
actually what is the problem then if it send correct amount of data? do you mean you don’t want the EOF? ---
**Author:** ![hkiol](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/hkiol/32/5998_2.png) [@hkiol](https://forum.sierrawireless.com/u/hkiol)\ **Post date:** [May 2, 2023, 6:56am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/9 "2023-05-02T06:56:58Z")
Server sends correct amount but modem reads less bytes ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 2, 2023, 6:58am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/10 "2023-05-02T06:58:18Z")
then if you don’t see problem in +KTCPSTART, that means it is network issue, right? ---
**Author:** ![hkiol](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/hkiol/32/5998_2.png) [@hkiol](https://forum.sierrawireless.com/u/hkiol)\ **Post date:** [May 2, 2023, 6:59am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/11 "2023-05-02T06:59:10Z")
I haven’t tried KTCPSTART yet. What is the difference with KTCPCNX? ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 2, 2023, 7:00am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/12 "2023-05-02T07:00:07Z")
it is different command to +KTCPCNX you can see AT command user guide Here also says how to capture wireshark log in HL7800 to verify if this is network problem: > [@+KTCP\_NOTIF: 1,8 with correct data length sent](https://forum.sierrawireless.com/t/ktcp-notif-1-8-with-correct-data-length-sent/19255/9): > > Hi Cherokee, notification of the following received packet is sent only when the current +KTCP\_DATA has been read with a +KTCPRCV command. My understanding is that after transmission, received data unsolicited indication should appear after dropping back to command mode. Once this message is received, you then issue AT+KTCPRSV=,. If is less than the first , then you will continue to receive +KTCP\_DATA notifications until all data is read. However, this indication needs to be received aft… ---
**Author:** ![hkiol](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/hkiol/32/5998_2.png) [@hkiol](https://forum.sierrawireless.com/u/hkiol)\ **Post date:** [May 2, 2023, 7:06am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/13 "2023-05-02T07:06:26Z")
Ok, so could it be that multiple KTCPDATA messages appear and the payload is split into different packets? ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 2, 2023, 7:07am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/14 "2023-05-02T07:07:08Z")
you need to capture the wireshark on module side to understand this ---
**Author:** ![hkiol](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/hkiol/32/5998_2.png) [@hkiol](https://forum.sierrawireless.com/u/hkiol)\ **Post date:** [May 2, 2023, 7:08am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/15 "2023-05-02T07:08:31Z")
Ok, will get back on this. Thanks ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 2, 2023, 7:09am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/16 "2023-05-02T07:09:16Z")
you might need to also try with +KTCPSTART to get more clue ---
**Author:** ![hkiol](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/hkiol/32/5998_2.png) [@hkiol](https://forum.sierrawireless.com/u/hkiol)\ **Post date:** [May 2, 2023, 7:11am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/17 "2023-05-02T07:11:20Z")
I just realized that what’s happening is the payload is split into packets and I have to continue sending KTCPRCV command to get the whole payload. That’s tricky to manage. Is that something the modem itself is doing, just for reference? ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 2, 2023, 7:13am UTC](https://forum.sierrawireless.com/t/ktcp-data-limit-on-hl7800/29667/18 "2023-05-02T07:13:08Z")
probably yes, might also depends on how fast the host reads the data