tcpblast: 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/sbin/tcpblast - from package: netdiag

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

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