tcpspy: 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/tcpspy - from package: tcpspy

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

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