nc: 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/nc - from package: nc

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

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