https://devzone.nordicsemi.com/f/nordic-q-a/88685/nrf91---maximizing-nb-iot-data-throughputHi, I&#180;ve been trying to improve data transmission from an nRF91 dev board through nb-iot to Azure IOT-hub and always got a socket disconnection event when I tried to send too much. Found out it probably had to do with the tx buffer for TLS transmissionsen-USTelligent Community 13Wed, 08 Jun 2022 12:14:11 GMThttps://devzone.nordicsemi.com/thread/371391?ContentTypeID=1Wed, 08 Jun 2022 12:14:11 GMT137ad170-7792-4731-bb38-c0d22fbe4515:76798e1d-ee1e-4d05-88f0-5095ace258d7Albrecht Markus Schellenberger<p>Hello Atli,</p> [quote user=""]I´ve been trying to&nbsp;improve data transmission from an nRF91 dev board through nb-iot to Azure IOT-hub and always got a socket disconnection event when I tried to send too much. [/quote] <p><span>Socket disconnection might be an issue with libmodem &lt; 2.0.0. The suggestion from our developers is to try NCS v2.0.0 with libmodem v2.0.1+b1. </span><span>Additionally, you can&nbsp;turn on CONFIG_NRF_MODEM_LOG for some helpful messages.</span><span>&nbsp;</span></p> [quote user=""]The function&nbsp;<span>azure_iot_hub_send</span><span>(&amp;msg) seems to stall (~400 - 700ms) after several transmissions (like it´s waiting to send the buffer to the cellular tower) or the socket disconnects.</span>[/quote] <p><span>As for the stalling, that&#39;s to be expected when the application sends more data than how much the modem can transmit on-air with the time it is given by the cellular network. Data to be sent on air is buffered, and when that buffer is full send() waits for memory at the socket as per POSIX.</span></p> <p><span>Cheers,</span></p> <p><span>Markus</span></p><div style="clear:both;"></div>