osc-send: 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/osc-send - from package: python-txosc

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

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