emacsclient: 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 CentOS possible default full paths are:

/usr/bin/emacsclient - from package: emacs-common

You may install the required package with command yum install {package}

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