Install Busybox and run ftp daemon on router

1. tftp -g -r busybox-mipsel 192.168.0.100
2. chmod 777 busybox-mipsel
3. ./busybox-mipsel tcpsvd -vE 0.0.0.0 21 /tmp/busybox-mipsel ftpd /
4. Finish

* "busybox-mipsel" static binary load from https://busybox.net/downloads/binaries/

* Username/Password find in /etc/passwd