tcpspray: 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/tcpspray - from package: ndisc6

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

On Debian possible default full paths are:

/usr/bin/tcpspray - from package: netdiag

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

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