Subscribe and Publish in BASH like a receive Buffer - bash

Question

I want to buffer all messages of a subscription during processing publish messages.
The reason is a firmware update over MQTT. I want to send data with crc and the microcontroller have to verify the content and need to answer with new address pointer.
For now, i got it working without any interaction from the microcontroller. If size doesn't fit, or mc is not online, my bash script sends all the data of the binary file into the nirvana.
If I publish a message and subscribe directly after the publish, it is possible to lose an answer very easily.
But I'm not so experienced with bash and I need some suggestions how to do this...
This is what I have:
mosquitto_pub -h $MQTT_SERVER -t "spiffs/${client_name}/file_info" -m "$binary_file" -p 8883 -i "fw_server" --cafile server-cert.pem -d --insecure -u $MQTT_USER -P $MQTT_PW
mosquitto_sub -h $MQTT_SERVER -p 8883 -t "+/${client_name}/#" -i "fw_server" --cafile server-cert.pem -d --insecure -u $MQTT_USER -P $MQTT_PW | while read -r payload
do
fp_jq_rspCode=".upload.fp" # file pointer
address=$(echo $payload | jq -r $fp_jq_rspCode)
echo "${payload}" | jq -c '.[]'
echo "address pointer:$address"
c=${address}
addr=$(printf '%08x' "$c")
content=$(xxd -p -c $payload_size -l $payload_size -seek $c $binary_file)
length=`expr length "$content"`
len=$(printf '%04x' "$length")
crc32=$(echo -n "$content" | gzip -c | tail -c8 | hexdump -n4 -e '"%u"')
crc32=$(printf '%08x' "$crc32")
echo "$addr $len $content $crc32"
message=$(printf '%08x%04x%s%s' "$c" "$length" "$content" "$crc32")
mosq=$(mosquitto_pub -h $MQTT_SERVER -t "spiffs/${client_name}/upload" -m "$message" -p 8883 -i "fw_server" --cafile server-cert.pem -d --insecure -u $MQTT_USER -P $MQTT_PW)
done