how to download mtdblock with netcat

[A.W.C.]

BusyBox v1.4.2: how to download mtdblock /dev/mtdblock3 from remote device (embedded Linux) to local computer with netcat command?

mtd blocks:

# cat /proc/mtd
dev:    size   erasesize  name
mtd0: 00020000 00010000 "U-Boot"
mtd1: 00010000 00010000 "env1"
mtd2: 00010000 00010000 "env2"
mtd3: 003a0000 00010000 "UBFI1"
mtd4: 003a0000 00010000 "UBFI2"
mtd5: 000cf6f4 00010000 "Kernel"
mtd6: 002cc800 00010000 "RootFileSystem"
mtd7: 00070000 00010000 "nvram"