tcpprof: 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/tcpprof - from package: tcpstat

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

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