simple example xsbug proxy

Author: phoddie

tools/xsbugproxy/index.js

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+const net = require('node:net');
+
+const proxyPortIn = 5004;		// proxy listening port
+
+/*
+	Moddable SDK prrojects connect to xsbug at loaclhost:5002.
+	This proxy listens on loaclhost:5004. To get the Noddable SDK project to connect to the proxy
+	requires a manual source code change. On macOS, in $MODDABLE/xs/platforms/mac_xs.c, change 
+		address.sin_port = htons(5002);
+	to
+		address.sin_port = htons(5004);
+	Linux and Windows have similar changes. Eventuall We can add an option to mcconfig to set the xsbug
+	port. 
+*/
+
+const proxyPortOut = 5002;		// xsbug listening port
+const trace = false;				// trace progress to console for debugging 
+const relay = true;
+/*
+	When relay is true, proxy relays messages between Moddable SDK project and xsbug.
+		This allows using xsbug as usual while proxy has access to all communication.
+	When relay is false, no cconnection is made to xsbug. The Moddabe SDK project sends
+		messages as-if xsbug is present.
+*/ 
+
+const server = net.createServer(target => { 
+	if (trace)
+		console.log('target connected');
+
+	let xsbug;
+	if (relay) {
+		// connect to xsbug to be able to relay messages
+		xsbug = net.connect({
+			port: proxyPortOut,
+			host: "localhost"
+		});
+		xsbug.setEncoding("utf8");
+		xsbug.on('ready', data => {
+			while (xsbug.deferred.length)
+				xsbug.write(xsbug.deferred.shift());
+			delete xsbug.deferred;
+		});
+		xsbug.on('data', data => {
+			if (trace)
+				console.log("from xsbug: " + data);
+			target.write(data);
+		});
+		xsbug.on('end', () => {
+			if (trace)
+				console.log('xsbug disconnected');
+			target.destroy();
+		});
+		xsbug.deferred = [];
+		xsbug.deferred.push("2");
+	}
+	else {
+	}
+
+	target.setEncoding("utf8");
+	let first = true;
+	target.on('data', data => {
+		if (trace)
+			console.log("to xsbug: " + data);
+		
+		// parse messages here
+		// each message is an XML document
+		// status messages are sent in a bubble right message of the form:
+		// <xsbug><bubble name="" value="2" path="/Users/hoddie/Projects/moddable/examples/helloworld/main.js" line="18">JSON STATUS MESSAGE HERE</bubble></xsbug>
+
+		if (relay) { 
+			if (xsbug.deferred)
+				xsbug.deferred.push(data);
+			else
+				xsbug.write(data);
+		}
+		else {
+			if (first) {
+				// first time need to send set-all-breakpoints as xsbug does
+				first = false;;
+				target.write('<set-all-breakpoints><breakpoint path="exceptions" line="0"/></set-all-breakpoints>\r\n');
+			}
+			else {
+				// assume any other messages are a break, so send go. This isn't always corrrect but may always work.
+				target.write('<go/>\r\n');
+			}
+		}
+	});
+	target.on('end', () => {
+		if (trace)
+			console.log('target disconnected');
+		if (xsbug)
+			xsbug.destroy();
+	});
+});
+
+server.listen(proxyPortIn, () => { 
+   console.log('proxy listening');
+});

tools/xsbugproxy/package.json

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+{
+  "dependencies": {
+    "ws": "^8.8.0"
+  }
+}