helloserver: 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/helloserver - from package: libpion-dev

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

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