xmlrpc_cpp_proxy: command not found

Have You tried accessing the binary with the full path?

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/xmlrpc_cpp_proxy - from package: xmlrpc-c-apps

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