1)
On utilise la commande	ncat -u -l -v -p 50000

Ncat: Version 7.94 ( https://nmap.org/ncat )
Ncat: Listening on [::]:50000
Ncat: Listening on 0.0.0.0:50000

sur un autre terminal on utilise la commande ss -lnu

UNCONN     0    0   0.0.0.0:50000   0.0.0.0:*


2)

dd if=/dev/zero of=ft-file.dat bs=1K count=9

9+0 records in
9+0 records out
9216 bytes (9.2 kB, 9.0 KiB) copied, 0.0083619 s, 1.1 MB/s


ls -lh ft-file.dat
-rw-r--r-- 1 solar students23 9.0K Mar 12 14:52 ft-file.dat