tcp_relay: 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/bin/tcp_relay - from package: knews

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

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