init.sqf - Init script on client side

hint "Message on client";

player addAction ["Send Message",
{
  sendThisMessage = "This is my message";
  publicVariableServer "sendThisMessage";
}];

initServer.sqf - Init script on server side

"sendThisMessage" addPublicVariableEventHandler
{
  _message = (_this select 1);
  _message remoteExec [ "hint", 0, true];
};