Running VS Code (code-server) in Termux: Solving the Annoying MAC Address Error

For developers looking to get a full desktop-grade code editing experience on their Android devices, VS Code is an incredibly attractive option. Thanks to Termux, a powerful terminal emulator and Linux environment, and the code-server project (which allows VS Code to run on a remote server and be accessed via a browser), we can set up a fairly complete development environment on an Android tablet or even a phone.

This article documents my process of installing and running code-server on an Android device via Termux, focusing on resolving a common and frustrating error: "Error: Unable to retrieve mac address (unexpected format)". The installation process I initially followed can be found on the official Coder website: https://coder.com/docs/code-server/termux

The Problem: "Error: Unable to retrieve mac address (unexpected format)"

After successfully installing code-server and attempting to run it, the service would start, but during operation (especially when trying to open a terminal or perform certain actions), an error would intermittently appear in the code-server logs or even as a pop-up in the VS Code interface:

Error: Unable to retrieve mac address (unexpected format)

After some investigation, the root cause was identified: Android's security policies. To protect user privacy, Android (since version 6.0) restricts applications from accessing Wi-Fi and Bluetooth MAC addresses. When a Node.js application like code-server calls the os.networkInterfaces() function to get network interface information, the Android system returns a placeholder MAC address of "00:00:00:00:00:00" for all interfaces.

code-server, or one of its underlying dependencies, interprets this all-zero MAC address as an invalid or unexpected format, leading to the error and disrupting its normal operation.

The Solution: Dynamically "Fixing" the MAC Address at Runtime

Since the issue stems from the value returned by os.networkInterfaces(), the solution is to modify this function's behavior when Node.js (and thus code-server) starts. We can make it return a MAC address format that code-server finds acceptable.

Here's how to implement this:

Step 1: Create the Patch Script

We'll create a small JavaScript file. This script will be executed by Node.js just before code-server itself starts. Let's name this file p.js and place it in the Termux home directory (/data/data/com.termux/files/home/p.js).

This script does the following:

1. It redefines process.platform to always return "linux". This can help ensure code-server and its dependencies behave as if they are on a standard Linux system, potentially avoiding other platform-specific issues.
2. It wraps the original os.networkInterfaces() function. The new function calls the original one, then iterates through the network interface details and replaces the problematic MAC address with a valid, dummy MAC address.

Here's the content for /data/data/com.termux/files/home/p.js:

JavaScript

console.log("patching started.");
Object.defineProperty(process, "platform", { get() { return "linux" }, });

const os = require('os');
var old_networkInterfaces = os.networkInterfaces;
// console.log(old_networkInterfaces);
function wrap_net() {
    var networkInterfaces = old_networkInterfaces();
        
    for (const iface in networkInterfaces) {
        if (networkInterfaces[iface]) {
            networkInterfaces[iface].forEach(details => {
                details.mac = '00:00:00:11:11:11'; // A fixed, acceptable MAC address
            });
        }
    }
    return networkInterfaces;
}

os.networkInterfaces = wrap_net;
// console.log(os.networkInterfaces());
// console.log(os.platform);
// console.log(os.networkInterfaces);

console.log("patching over.");

Step 2: Configure Node.js to Preload the Patch Script

Node.js has an environment variable called NODE_OPTIONS that allows you to pass command-line options to the Node.js runtime. We'll use the --require option to tell Node.js to load and execute our p.js script before starting code-server.

You'll need to modify the command or script you use to launch code-server. Here's an example of a shell script you could use (e.g., start-code-server.sh in your Termux home directory):

Bash

#!/bin/bash

# Set NODE_OPTIONS to make Node.js require our patch script at startup
export NODE_OPTIONS="--require /data/data/com.termux/files/home/p.js" 

# Start code-server
# --auth=none: Disables password authentication (ensure your device/network is secure, or use a reverse proxy for auth)
# --disable-telemetry: Disables sending telemetry data
code-server --auth=none --disable-telemetry 

# For more verbose logging during debugging, you could add -vvv
# code-server --auth=none --disable-telemetry -vvv

Make this script executable:

chmod +x /data/data/com.termux/files/home/start-code-server.sh

Now, when you run /data/data/com.termux/files/home/start-code-server.sh:

1. The NODE_OPTIONS environment variable instructs Node.js to first load and execute the /data/data/com.termux/files/home/p.js script.
2. Our p.js script modifies process.platform and overrides os.networkInterfaces().
3. code-server then starts. When it calls os.networkInterfaces(), it gets the modified network interface data with the acceptable MAC address.

With this patch in place, the "Error: Unable to retrieve mac address (unexpected format)" error should no longer occur, allowing code-server to run smoothly on your Android device via Termux.

Conclusion

Running code-server in Termux on an Android device is a fantastic way to have a portable and powerful development environment. While Android's security measures can sometimes create minor obstacles like the MAC address issue, understanding the problem allows for elegant workarounds.

By dynamically patching the os.networkInterfaces function at Node.js startup, we provide code-server with a MAC address it can process, effectively resolving the error. Hopefully, this detailed solution helps others who encounter this specific problem, enabling a smoother VS Code experience on Android!