The brscan-skey utility is configured to use the eth0 network adapter by default.
 

If you are using a different network adapter, or if the name of the default network adapter is not eth0 (e.g. Debian4.0r3), you will have to configure it by manual:

Confirm the network adapter name which is used for the connection with the scanner (e.g. eth0, eth1).
You can confirm the network adapter name by "ifconfig" command.
 

Open /usr/local/Brother/sane/brscan-skey-(version).cfg using your preferred text editor.

Add the line "eth=(adapter name)" to the cfg file. Change the adapter name accordingly.

Restart the scan-key program ("brscan-skey -t" to terminate the program and "brscan-skey" to start.)
*** It may take a few minutes for the modification to take effect.

Example of an edited file
--------------------------------------------------------------
eth=eth1
IMAGE="sh /usr/local/Brother/sane/script/scantoimage-0.2.1-1.sh"
OCR="sh /usr/local/Brother/sane/script/scantoocr-0.2.1-1.sh"
EMAIL="sh /usr/local/Brother/sane/script/scantoemail-0.2.1-1.sh"
FILE="sh /usr/local/Brother/sane/script/scantofile-0.2.1-1.sh"
SEMID=b
--------------------------------------------------------------"