cwnnstat: command not found

Have You tried accessing the binary with the full path?

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/sbin/cwnnstat - from package: freewnn-cserver

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