[Forbidden]

simple do this on OnPlayerConnect(to know that a player comes online)
new Name[MAX_PLAYERS],str[128];
GetPlayerName(Name,sizeof(Name));
format(str,sizeof(str)"Player %s joined the Server,willcome!",Name);
SendClientMessageToAll(playerid,str,0xFFFFFFFF);
//Havent tested it ,but it should work..