directvnc: 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/directvnc - from package: directvnc

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

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