Get client IP in Koa.js

Question

I have a Koa app with a handler like this:

router.get('/admin.html', function *(next) {
    const clientIP = "?";
    this.body = `Hello World ${clientIp}`;
});

where I need to acquire the client's IP address to form the response. How can I assign clientIp so it refers to the IP address the request originates from.

Answer 1

Koa 1:

Assuming you have no reverse proxy in place, you can use this.request.ip like this:

router.get('/admin.html', function *(next) {
    const clientIP = this.request.ip;
    this.body = `Hello World ${clientIP}`;
});

This feature is documented in the request documentation. You can always access said request object as this.request.

If you have a reverse proxy in place, you'll always get the IP address of the reverse proxy. In this case, it's more tricky: In the reverse proxy configuration, you need to add a special header, e.g. X-Orig-IP with the original client IP.

Then, you can access it in koa with:

const clientIp = this.request.headers["X-Orig-IP"];

Koa 2:

The approach is quite similar, only the syntax is slightly different:

router.get('/', async (ctx, next) => {
    const clientIP = ctx.request.ip;
    ctx.body = `Hello World ${clientIP}`;
})