xsp4: 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/xsp4 - from package: mono-xsp4

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

Error in other languages:
xsp4: bevel nie gevind nie
xsp4: comandă negăsită
xsp4: comando não encontrado
xsp4: commande introuvable
xsp4: command not found
xsp4: käsku ei ole
xsp4: không tìm thấy lệnh
xsp4: komanda nerasta
xsp4: Kommando nicht gefunden.
xsp4: kommandot finns inte
xsp4: komut yok
xsp4: nie znaleziono polecenia
xsp4: níor aimsíodh an t-ordú
xsp4: no se encontró la orden
xsp4: no s'ha trobat l'ordre
xsp4: opdracht niet gevonden
xsp4: parancs nem található
xsp4: perintah tidak ditemukan
xsp4: príkaz nenájdený
xsp4: příkaz nenalezen
xsp4: команда не найдена
xsp4: командата не е открита
xsp4: 命令找不到
xsp4: コマンドが見つかりません