What is port forwarding?

June 17, 2024
min read
Team ngrok

Port forwarding is a networking technique that allows devices and servers outside a protected private network to access applications, services, or devices running inside that network. That access is provided by mapping a port on the private network’s gateway–such as a router or firewall–to an address inside the network. Think of it as opening a specific "door" on the private network to let in and route particular types of traffic to services to be accessed.

In the world of networking, these "doors" are called ports. Each port receives a unique number, and by configuring your router or firewall to forward traffic from an external port to a specified internal port, you can selectively grant access to internal applications or services.

What Is port forwarding used for?

Port forwarding serves a variety of purposes, particularly in development, gaming, and remote administration.

Remote management enables system administrators to remotely access and manage servers and devices on a network. This allows them to perform tasks such as installing updates, configuring settings, or troubleshooting issues without needing to be physically present.

In web development, developers can share and test web applications running locally with colleagues or clients. This access allows colleagues and clients to provide feedback on the web applications without requiring the developers to take the extra steps of deploying to an external server.

For online gaming, port forwarding allows you to host online multiplayer games on your home network. It directs game traffic from the internet to the appropriate device and port on your local network, enabling external players to connect seamlessly.

How port forwarding works

Let's say you want to host an online game for your friends or share a website you're building. Port forwarding makes this possible by letting people outside your network connect to specific devices inside. Here's how it works:

  1. The incoming request: The external device sends a request to your network’s public IP address.
  2. The router intercepts: Your router intercepts the request using NAT (network address translation). However, it doesn't yet know which specific device inside your network needs to receive it.
  3. The rules: Your router checks its port-forwarding rules, which outline which public port is associated with which internal device and port.
  4. Redirecting traffic: The router uses those rules to redirect the incoming request to the designated internal device and port.
  5. The connection established: The internal device receives the request and responds, thus creating a connection between the external device and your internal device.

Think of your router as a receptionist for your network. When someone outside your network tries to connect (like calling the office), the router uses its "directory" (the port-forwarding rules) to decide which device inside should receive the connection.

This process is like opening a specific "door" in your network, allowing external devices to communicate directly with those devices inside.

Risks of port forwarding

While port forwarding offers convenience, it's crucial to be aware of its inherent risks:

Exposing applications directly to the internet introduces significant security vulnerabilities. It is akin to leaving your front door unlocked, making your applications susceptible to attacks, malware, and unauthorized access. Hackers could exploit these vulnerabilities, leading to data breaches and service disruptions that compromise your entire network.

Port forwarding also presents complexity challenges. It requires technical expertise and careful configuration, which can pose difficulties, especially for beginners without networking experience. The dynamic nature of IP addresses adds another layer of complexity, complicating the setup and maintenance process. Improper configuration can result in unintended consequences, including security vulnerabilities or network disruptions.

Use ngrok as a secure and simplified alternative

We think ngrok is a great option for developers and administrators who need to expose internal applications to the internet, but who are concerned about the risks of traditional port forwarding.

One of the primary benefits of this system is its user-friendly nature, allowing access to internal applications without requiring complex router configurations. Additionally, it enhances security by eliminating the risks associated with traditional port forwarding.

ngrok features secure tunnels, creating protected connections between your local applications and the internet. The platform provides publicly accessible URLs that map to your internal ports. ngrok can generate dynamic URLs, or you can provide your own custom domains, making it easy to access your internal applications. 

In terms of security, ngrok utilizes TLS encryption to safeguard communication between the applications on your private network and the public internet. This ensures that data transmitted through the tunnels is encrypted and protected from unauthorized access, offering a higher level of security compared to traditional port forwarding.

Port forwarding is a fundamental networking concept that can help share and access internal applications. However, its complexity and security risks make it a less ideal solution for those who prioritize ease of use and security. ngrok provides a safer and more convenient option, enabling developers and administrators to expose their internal applications to the internet with enhanced security and simplified workflows. If you have questions, issues, or features to request, you can always find us on X or email us directly at support@ngrok.com.

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