hping3: 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 CentOS possible default full paths are:

/usr/sbin/hping3 - from package: hping3

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/sbin/hping3 - from package: hping3

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

Error in other languages:
hping3: bevel nie gevind nie
hping3: comandă negăsită
hping3: comando não encontrado
hping3: commande introuvable
hping3: command not found
hping3: käsku ei ole
hping3: không tìm thấy lệnh
hping3: komanda nerasta
hping3: Kommando nicht gefunden.
hping3: kommandot finns inte
hping3: komut yok
hping3: nie znaleziono polecenia
hping3: níor aimsíodh an t-ordú
hping3: no se encontró la orden
hping3: no s'ha trobat l'ordre
hping3: opdracht niet gevonden
hping3: parancs nem található
hping3: perintah tidak ditemukan
hping3: príkaz nenájdený
hping3: příkaz nenalezen
hping3: команда не найдена
hping3: командата не е открита
hping3: 命令找不到
hping3: コマンドが見つかりません