Inspecting Node.js Traffic with Charles

A good web debugging proxy like Charles can be incredibly valuable when building mobile or web apps that are intended to talk to others. Charles (and Fiddler) will automatically configure itself as a proxy for your browser traffic, but configuring it to work properly in other environments (especially those that require SSL) requires a bit more finesse.

Recently, I used tunnel, to push requests from a Node.js application through Charles in order to debug an issue. Below is a quick recap.

First, save the Charles Root Certificate (Help > SSL Proxying > Save Charles Root Certificate):

Save Charles Root Certificate (charles-ssl-proxying-certificate.pem) via Help menuNext, include tunnel in your application:

var tunnel = require("tunnel")Finally, before setting up any HTTPS requests, configure tunnel to utilize your proxy:

var tunnelAgent = tunnel.httpsOverHttp({  
 ca: [fs.readFileSync('charles-ssl-proxying-certificate.pem')],  
 proxy: {  
 host: '127.0.0.1',  
 port: 8888  
 }  
});

Launch Charles, run your application, and watch that network traffic flow in. Simple.