xp_usage
return (xp_usage("invalid port for -p: %d\n",
return (xp_usage("-%c requires an operand\n", optopt));
return (xp_usage("unknown option: -%c\n", optopt));
return (xp_usage("-l cannot be used with other options\n"));
return (xp_usage("-c and -s can't be used together\n"));