udppm: 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/bin/udppm - from package: 3proxy

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

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