An MQTT subscription utility (for use with jsexec)

Similar to (mimics) mosquitto_sub

exec/mqtt_sub.js

+// A simple MQTT subscriber, for use with jsexec [-f]
+// Command-line options more or less mimic 'mosquitto_sub'
+
+"use strict";
+
+const default_topic = "sbbs/#"
+var mqtt = new MQTT;
+var json = false;
+var verbose = false;
+var topic = [];
+var count = 0;
+var newline = true;
+var options = {};
+
+for(var i = 0; i < argc; ++i) {
+	var arg = argv[i];
+	while(arg[0] === '-')
+		arg = arg.substring(1);
+	switch(arg) {
+		case 'C':
+			count = parseInt(argv[++i], 10);
+			break;
+		case 'N':
+			newline = false;
+			break;
+		case 'h':
+			mqtt.broker_addr = argv[++i];
+			break;
+		case 'p':
+			mqtt.broker_port = parseInt(argv[++i], 10);
+			break;
+		case 'q':
+			mqtt.subscribe_qos = parseInt(argv[++i], 10);
+			break;
+		case 't':
+			topic.push(argv[++i]);
+			break;
+		case 'v':
+			verbose = true;
+			break;
+		case '?':
+		case 'help':
+			print("options:");
+			print("  -h  MQTT broker hostname or IP address, default: " + mqtt.broker_addr);
+			print("  -p  MQTT TCP port number to use, default: " + mqtt.broker_port);
+			print("  -q  QoS value to use, default: " + mqtt.subscribe_qos);
+			print("  -N  do not append newline to printed messages");
+			print("  -t  Topic to subscribe to (can be repeated), default: " + default_topic);
+			print("  -v  Use verbose output (include topic)");
+			print("  -json Output in JSON format (add -pretty for prettier JSON)");
+			exit(0);
+		default:
+			options[argv[i].slice(1)] = true;
+			break;
+	}
+}
+
+if(!mqtt.connect()) {
+	alert(format("Error (%s) connecting to %s:%u", mqtt.error_str, mqtt.broker_addr, mqtt.broker_port));
+	exit(1);
+}
+if(!topic.length)
+	topic = [default_topic];
+for(var i in topic) {
+	if(!mqtt.subscribe(topic[i])) {
+		alert(format("Error (%s) subscribing to %s", mqtt.error_str, topic[i]));
+		exit(1);
+	}
+}
+var msgs_received = 0;
+var outfunc = newline ? print : write;
+while(!js.terminated) {
+	var msg = mqtt.read(1000, /* object retval: */true);
+	if(msg === false) {
+		continue;
+	}
+	if(options.json)
+		outfunc(JSON.stringify(msg, null, options.pretty ? 4 : 0));
+	else {
+		if(verbose)
+			printf("%s ", msg.topic);
+		outfunc(msg.data);
+	}
+	++msgs_received;
+	if(count && msgs_received >= count)
+		break;
+}