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 after the transmission first, in order to know how many bytes to receive in the first place. I suppose one way to deal with this is to send a At+KTCPRCV=1,1000 and just try to receive bytes. However, if the +KTCP_DATA notification does not show up after the packet transmission is completed, then no data is available anyway.