talkd: 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/talkd - from package: inetutils-talkd

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

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