Ngrok is an exceptional tool that solves many problems you may face while working with actually-hosted applications. This tool can create a secure tunnel between your local machine and the internet. However, in some cases, you may find yourself facing an 'invalid host header' error while trying to use ngrok. In this article, we will take a closer look at why you might encounter this error and how to resolve it.
Understanding the 'Invalid Host Header' issue
When a server receives a request without a required Host header that defines the request's expected hostname, an error occurs called the 'Invalid Host Header' issue. The Host header is mandatory in HTTP 1.1, and it's invalid when it doesn't match the requested host. Here's an example –
GET / HTTP/1.1
Accept: */*
Connection: keep-alive
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.122 Safari/537.36
The Host header is missing from this request, and thus, it returns the 'Invalid Host header' error code.
Reasons for the 'Invalid Host Header' Error in Ngrok
When you're using the ngrok tunneling service, there are several reasons why you could experience the 'Invalid Host Header' issue. Here are some of them:
-
Reverse proxying: If you're using a reverse proxy, the Host header may get mismatched with the actual hostname.
-
Setup Incorrectly: If you have misconfigured your ngrok settings or are using an outdated version, you may face the 'Invalid Host Header' error.
-
Port Mismatch: Another reason for the 'Invalid Host Header' error occurs when the port number or hostname mismatches.
Resolving the 'Invalid Host Header' Error
There are several methods to resolve the 'Invalid Host Header' error in ngrok, depending on the reason for the error. Here are some of the most common ways to solve this problem –
- Valid Host Header
The easiest method of resolving the 'Invalid Host Header' issue in ngrok is by supplying a valid host header to the requesting source. To achieve this, set a Host header with the correct hostname that closely matches the actual hostname. Here's some Node.js code that shows how to add a host header:
const http = require('http')
const opts = {
host: 'localhost',
port: 8080,
path: '/',
headers: {
Host: 'example.com'
}
}
const req = http.request(opts, (res) => {
console.log(res.statusCode)
res.pipe(process.stdout)
})
req.end()
- ngrok reconfiguration
Another method to fix the 'Invalid Host Header' error in ngrok is to reconfigure the ngrok service. One of the ways to fix ngrok's configuration is by updating it to the latest version.
You can update ngrok simply by running the command below in the terminal to get the latest version:
npm update ngrok
- Using the right port
If your ngrok tunnel uses the wrong port, you may also experience the 'Invalid Host Header' error. To resolve this issue, make sure that the port number used in your configuration matches the port number used in the requesting URL.
Bottom Line
The 'Invalid Host Header' error in ngrok is an unfortunate problem that can prevent you from accessing your locally hosted application. The possible reasons for this issue include reverse proxying, set up incorrectly, and port mismatch. To resolve the problem, you can use any of the methods discussed above. With the above solutions, you can have your locally hosted application up and running in no time.
let's dive a little deeper into some of the topics that were touched upon in the previous article.
Reverse Proxying and the Host Header
One of the potential reasons for the 'Invalid Host Header' error in ngrok is due to reverse proxying. A reverse proxy is a server that sits between the client and the actual web server to handle requests. The reverse proxy can handle client requests, serve static assets, and route traffic to different web servers based on various conditions. For example, you might use a reverse proxy to split traffic between multiple web servers in a load-balancing scenario.
When you use a reverse proxy, the Host header can potentially get mismatched with the actual hostname. This situation can happen if the reverse proxy is not configured to pass on the Host header to the actual web server or if it changes the Host header in some way.
To fix this issue, you can ensure that the reverse proxy is properly configured to pass on the correct Host header to the actual web server. How you configure this can depend on the specific reverse proxy you are using. For example, in Nginx you might use the 'proxy_set_header' directive to set the Host header when proxying to the actual server.
Port Mismatch and the Host Header
Another potential reason for the 'Invalid Host Header' error is due to a port mismatch. When ngrok sets up a tunnel to localhost, it typically binds to a specific port number on the external internet-facing endpoint. This endpoint is where the requests will be coming from when accessing your locally hosted application.
If the port number used by ngrok when setting up this endpoint does not match the port number being used by your locally hosted application, you may encounter the 'Invalid Host Header' error. This is because the Host header in the incoming requests will not match the expected hostname of the application, which can result in the error.
To fix this issue, you can ensure that the port number used by ngrok matches the port number being used by your locally hosted application. You should be able to configure the port number used by the ngrok endpoint in the ngrok configuration file or in the command line arguments used to start the ngrok service.
Conclusion
The 'Invalid Host Header' error in ngrok can be frustrating to deal with, but with some careful debugging and configuration, you should be able to overcome it and get your locally hosted application up and running as intended. By understanding some of the potential causes of this error, you can work towards finding a solution that works for your specific use case. Whether it's updating ngrok to the latest version, properly configuring a reverse proxy, or ensuring that the correct port number is being used, there are solutions available to help you resolve this error and move forward with your project.
Popular questions
- What is the 'Invalid Host Header' issue?
The 'Invalid Host Header' issue occurs when a server receives a request without a required Host header that defines the request's expected hostname. The Host header is mandatory in HTTP 1.1, and it's invalid when it doesn't match the requested host.
- What are some reasons for the 'Invalid Host Header' error in ngrok?
The 'Invalid Host Header' error can occur due to reverse proxying, incorrect ngrok configuration, or port mismatches.
- How can you fix the 'Invalid Host Header' error in ngrok?
You can fix the 'Invalid Host Header' error by supplying a valid host header, reconfiguring the ngrok service, or ensuring that the port number used by ngrok matches the port number being used by your locally hosted application.
- How can you add a host header using Node.js code?
You can add a host header using Node.js code by including the appropriate header in the HTTP request options, like this:
const http = require('http')
const opts = {
host: 'localhost',
port: 8080,
path: '/',
headers: {
Host: 'example.com'
}
}
const req = http.request(opts, (res) => {
console.log(res.statusCode)
res.pipe(process.stdout)
})
req.end()
- What is reverse proxying, and how can it cause the 'Invalid Host Header' error in ngrok?
Reverse proxying is when a server sits between the client and the actual web server to handle requests. The reverse proxy can handle client requests, serve static assets, and route traffic to different web servers based on various conditions. When a reverse proxy is not configured to pass on the Host header to the actual web server or changes the Host header in some way, it can cause the 'Invalid Host Header' error in ngrok.
Tag
NGROK_ERROR
