Support for spying via MQTT between nodes

For read-only spying, the mqtt_spy.js module can be used via jsexec (from an
OS shell command prompt), similar to mosquitto_sub.

For read-write spying, just use the ;SPY sysop command as before and if MQTT
is configured/enabled, it'll use MQTT rather than sockets or shared memory
queues to spy on the target node.

For the first time, you can spy between nodes that are on different servers of
the same BBS using the ;SPY sysop command.

Passes through ctrl characters (except Ctrl-C), unlike the built-in spy
function. This could be revisited later or made optional, but it sems to make
sense to allow Ctrl-Z (e.g. to save a message in fseditor.js) to be passed
through to the target node.

exec/mqtt_spy.js

+// Spy on a terminal server node using MQTT
+
+require("key_defs.js", "CTRL_C");
+require("nodedefs.js", "NodeStatus");
+
+"use strict";
+
+function get_ansi_seq()
+{
+	var seq = '';
+	var key;
+
+	while(key = ascii(console.getbyte(100))) {
+		seq += key;
+		if(key < '@' || key > '~')
+			continue;
+		switch(key) {
+			case 'A':	// Up
+			case 'B':	// Down
+			case 'C':	// Right
+			case 'D':	// Left
+			case 'F':	// Preceding line
+			case 'H':	// Home
+			case 'K':	// End
+			case 'V':	// PageUp
+			case 'U':	// PageDn
+			case '@':	// Insert
+			case '~':	// Various VT-220
+				// Pass-through these sequences to spied-upon node (eat all others)
+				return KEY_ESC + '[' + seq;
+		}
+		return null;
+	}
+	return null;
+}
+
+if(argc < 1) {
+	alert("Node number not specified");
+	exit(0);
+}
+
+var node_num = parseInt(argv[0], 10);
+if(node_num < 1 || node_num > system.nodes || isNaN(node_num)
+	|| (js.global.bbs != undefined && node_num == bbs.node_num)) {
+	alert("Invalid Node Number: " + node_num);
+	exit(0);
+}
+var in_topic = format("sbbs/%s/node/%u/input", system.qwk_id, node_num);
+var out_topic = format("sbbs/%s/node/%u/output", system.qwk_id, node_num);
+var status_topic = format("sbbs/%s/node/%u/status", system.qwk_id, node_num);
+var mqtt = new MQTT();
+if(!mqtt.connect()) {
+	alert("Connect error: " + mqtt.error_str);
+	exit(1);
+}
+if(!mqtt.subscribe(status_topic)) {
+	alert(format("Subscribe to '%s' error: %s", status_topic, mqtt.error_str));
+	exit(1);
+}
+var node_status = parseInt(mqtt.read(1000));
+if(!mqtt.subscribe(out_topic)) {
+	alert(format("Subscribe to '%s' error: %s", out_topic, mqtt.error_str));
+	exit(1);
+}
+print("*** Synchronet MQTT Spy on Node " + node_num + ": Ctrl-C to Abort ***\r\n");
+
+while(!js.terminated) {
+	var msg = mqtt.read(/* timeout: */10, /* verbose: */true);
+	if(msg) {
+		if(msg.topic == out_topic)
+			write(msg.data);
+		else if(msg.topic == status_topic) {
+			var new_status = parseInt(msg.data, 10);
+			if(new_status != node_status) {
+				node_status = new_status;
+				print("\r\nNew node status: " + NodeStatus[node_status]);
+			}
+		}
+	}
+	if(js.global.console) {
+		if(console.aborted || !bbs.online)
+			break;
+		console.line_counter = 0;
+		while(bbs.online) {
+			var key = ascii(console.getbyte(10));
+			if(!key)
+				break;
+			if(key == KEY_ESC) {
+				key = ascii(console.getbyte(500));
+				if(!key)
+					key = KEY_ESC;
+				else if(key != '[')
+					key = KEY_ESC + key;
+				else
+					key = get_ansi_seq();
+			}
+			mqtt.publish(in_topic, key);
+		}
+	}
+}
+print();
+print("Done spying");

exec/str_cmds.js

@@ -441,6 +441,9 @@ function str_cmds(str)
 				str=str.substr(3);
 				writeln("");
 				try {	// May throw on parseInt()
+					if(system.mqtt_enabled)
+						js.exec('mqtt_spy.js', this, parseInt(get_nodenum(str)));
+					else
 						bbs.spy(parseInt(get_nodenum(str)));
 					write("\1n\r\nSpy session complete.\r\n");
 				}