Using port number in Windows host file closed

Navigating the complexities of network configurations can be daunting, especially when dealing with the Windows hosts file. Many users are unaware of the power this simple text file holds, especially its ability to map hostnames to specific IP addresses and – critically – port numbers. Understanding how to use port numbers within your hosts file opens up a world of possibilities for local development, testing, and even troubleshooting network issues. This article dives deep into using port numbers in your Windows hosts file, providing clear explanations and practical examples to empower you to take control of your network routing.

Understanding the Hosts File

The hosts file acts as a local DNS resolver, overriding the system’s default DNS settings. It provides a way to directly map hostnames to IP addresses on your computer. This can be invaluable for web developers testing local websites, system administrators managing internal networks, and anyone needing precise control over network connections. By modifying the hosts file, you can redirect traffic to specific servers or even block unwanted connections.

Located at C:\Windows\System32\drivers\etc\hosts, the hosts file is a plain text document editable with any text editor. Each line represents a mapping, with the IP address followed by the hostname. Adding or modifying entries allows you to customize how your system resolves specific hostnames.

For example, adding the line 127.0.0.1 localhost maps the hostname “localhost” to the loopback IP address, ensuring any traffic directed to localhost stays on your machine. This is a default entry crucial for many applications.

Incorporating Port Numbers

While the standard hosts file usage involves mapping hostnames to IP addresses, it doesn’t directly support port numbers. Trying to add a port number directly to the hosts file, such as 127.0.0.1:8080 localhost, will simply be ignored by the system. The hosts file only handles hostname-to-IP resolution, not port mapping.

So, how can we achieve port-specific redirection? The solution lies in leveraging your operating system’s networking tools, specifically by configuring a local web server or utilizing tools like local proxies.

For instance, if you’re running a web server on port 8080, you can map a hostname to your local IP address (127.0.0.1) in the hosts file. Then, when you access that hostname in your browser, the request will be directed to your local machine, and your web server listening on port 8080 will handle the request. This effectively achieves port-specific redirection without modifying the hosts file’s structure.

Practical Examples and Use Cases

Consider a scenario where you’re developing a website locally. You could add an entry like 127.0.0.1 mytestsite.local to your hosts file. Now, accessing mytestsite.local in your browser will direct traffic to your local machine. If your local web server is configured to listen on port 8080, navigating to mytestsite.local:8080 will connect you to your locally hosted website.

Another example involves testing different versions of a website. By mapping different hostnames to your local IP address and configuring virtual hosts on your web server, you can easily switch between different website versions by simply changing the URL in your browser.

Redirecting internal services to specific ports is another useful application. For example, you can map a hostname like internal.database.local to your database server’s IP address and access it using internal.database.local:5432 if your database server listens on port 5432.

Troubleshooting and Advanced Configurations

Sometimes, issues can arise when using the hosts file. Common problems include incorrect syntax, typos in hostnames or IP addresses, and conflicting entries. Double-checking your entries and ensuring proper formatting is crucial for avoiding these issues.

For more advanced scenarios, you can leverage tools like local proxies to achieve finer control over port mapping. Proxies act as intermediaries between your browser and the destination server, allowing you to configure port forwarding and other advanced routing rules.

Remember to flush your DNS cache after modifying the hosts file to ensure the changes take effect. This can be done using the command ipconfig /flushdns in your command prompt.

Regularly review and clean up your hosts file to avoid unnecessary entries.
Use descriptive hostnames that reflect the services they point to.

Open the hosts file with a text editor.
Add the IP address and hostname.
Save the file.
Flush your DNS cache.

“Understanding the interplay between the hosts file, your web server, and your operating system’s networking stack is essential for effectively managing local development and testing environments.” - Network Engineering Expert

Learn More About NetworkingFeatured Snippet: While the hosts file doesn’t directly support port numbers, you can achieve port-specific redirection by combining hosts file entries with local web servers or proxy configurations.

[Infographic Placeholder] - Ensure the web server is running and listening on the intended port.

Verify the hostname in the hosts file matches the one used in the browser.

FAQ

Q: Can I use wildcards in the hosts file for port mapping?
A: No, wildcards are not supported for port numbers within the hosts file.

Mastering the hosts file provides significant control over local network routing. While port numbers aren’t directly supported within the file itself, combining it with other networking tools unlocks powerful possibilities for managing local development, testing, and troubleshooting. Explore the linked resources for further learning and elevate your networking skills. Dive deeper into network management by exploring related topics like DNS resolution, proxy servers, and virtual hosts. This knowledge will empower you to fine-tune your network environment and optimize your workflow.

Learn more about DNS

Learn more about Proxy Servers

Learn more about Virtual Hosts

Question & Answer :

After installing TeamViewer, I have changed the wampserver port to 8080, so the address is `http://localhost:8080.`

For the host file located at C:\WINDOWS\system32\drivers\etc\, I have also made the change as below

BEFORE
127.0.0.1 www.example.com

AFTER
127.0.0.1:8080 www.example.com

When I access www.example.com, it doesn’t redirect to my wampserver, how can I fix it?

I managed to achieve this by using Windows builtin networking tool netsh.

As Mat points out: The hosts file is for hostname resolution only, so a combination of the two did the trick for me.

Example

Overview

example.test:80 | <--Link by Hosts File +--> 127.65.43.21:80 | <--Link by netsh Utility +--> localhost:8081

Actions

Started my server on localhost:8081
Added my “local DNS” in the hosts file as a new line
```
127.65.43.21 example.test 
```
- Any free address in the subnet 127.0.0.0/8 (127.x.x.x) can be used.
- Note: I am assuming 127.65.43.21:80 is not occupied by another service.
  You can confirm this by checking the output of netstat -a -n -p TCP | grep "LISTENING"
Added the following network configuration, using netsh:
netsh interface portproxy add v4tov4 listenport=80 listenaddress=127.65.43.21 connectport=8081 connectaddress=127.0.0.1
I can now access the server at http://example.test

Notes:

These commands/file modifications need to be executed with Admin rights
netsh portproxy needs IPv6 libraries, even just to use v4tov4. Typically these will be installed by default, otherwise install with netsh interface ipv6 install

You can see the entry you have added with the command:

netsh interface portproxy show v4tov4

You can remove the entry with the following command:

netsh interface portproxy delete v4tov4 listenport=80 listenaddress=127.65.43.21

Domains forced to HTTPS via preloaded HSTS

I recently had the problem with a webserver that does not support https, only http, and I was constantly getting blocked

My Work-Around has been to use a name without a tld or one that is not known and use the forward slash at the ending. e.g.

hosts file: 127.0.1.101 aw

In Any case you can check if HTTPS is forced visiting chrome://net-internals/#hsts and Query HSTS/PKP domain , Result should be not Found

Links exposing attempts at certain workarounds:1, 2 These Workarounds attemp to add exceptions which should be able to be viewed in Insecure Sites and possibly also in the Redirection configuration sections

Here you will find a list of TLDs forced to HTTPS