netsend: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/netsend - from package: netsend

You may install the required package with command apt-get install {package}

Error in other languages:
netsend: bevel nie gevind nie
netsend: comandă negăsită
netsend: comando não encontrado
netsend: commande introuvable
netsend: command not found
netsend: käsku ei ole
netsend: không tìm thấy lệnh
netsend: komanda nerasta
netsend: Kommando nicht gefunden.
netsend: kommandot finns inte
netsend: komut yok
netsend: nie znaleziono polecenia
netsend: níor aimsíodh an t-ordú
netsend: no se encontró la orden
netsend: no s'ha trobat l'ordre
netsend: opdracht niet gevonden
netsend: parancs nem található
netsend: perintah tidak ditemukan
netsend: príkaz nenájdený
netsend: příkaz nenalezen
netsend: команда не найдена
netsend: командата не е открита
netsend: 命令找不到
netsend: コマンドが見つかりません