How to Use the Command 'upnpc' (with Examples)

upnpc is a command-line utility used for managing port forwarding rules on your router through the Universal Plug and Play (UPnP) protocol. UPnP is a networking protocol that enables devices to discover each other and establish network services for data sharing, communications, and entertainment. upnpc allows you to automate the configuration of port forwarding, a crucial network feature that redirects incoming traffic to a designated local machine, thereby facilitating services like hosting a web server or allowing online gaming traffic.

Use Case 1: Forward the External TCP Port 80 to Port 8080 on a Local Machine

Code:

upnpc -a 192.168.0.1 8080 80 tcp

Motivation:

Imagine you are hosting a web server on your local machine, which uses port 8080. However, to make your server accessible to others on the internet, you prefer to use the default HTTP port, which is port 80. This configuration simplifies access for users who do not need a specific port number to reach your server. Port forwarding makes this possible, and upnpc provides an easy and automated way to set it up without manually accessing complex router settings.

Explanation:

• upnpc: This is the command itself, which invokes the UPnP client.
• -a: This flag stands for “add” and is used to create a new port forwarding rule.
• 192.168.0.1: This is the IP address of the local machine to which the external TCP port 80 should forward traffic. Typically, this is the internal IP address of the host machine in your local network.
• 8080: This is the port number on the local machine where the requests coming to the external port 80 should be forwarded.
• 80: This is the external port number, visible outside the local network, that will be linked to port 8080 on your host machine.
• tcp: This specifies the protocol type, which is Transmission Control Protocol in this case.

Example Output:

TCP port 80 redirected to 192.168.0.1:8080

Use Case 2: Delete Any Port Redirection for External TCP Port 80

Code:

upnpc -d 80 tcp

Motivation:

Occasionally, you might need to remove port forwarding rules, perhaps for security reasons or because the service that required it is no longer running. Such clean-up measures are essential in managing network configurations, as unused port forwarding rules can represent potential security risks by leaving open entry points into your network.

Explanation:

• upnpc: This re-engages the utility to perform a new operation.
• -d: This flag indicates the intention to delete an existing port forwarding rule.
• 80: This refers to the external port number to which traffic forwarding is currently enabled and you wish to remove.
• tcp: This clarifies the protocol type for which the port forwarding is being deleted.

Example Output:

Successfully deleted 80 TCP redirection.

Use Case 3: Get Information about UPnP Devices on Your Network

Code:

upnpc -s

Motivation:

Gathering information about UPnP devices on your network can be incredibly useful for troubleshooting network issues, understanding existing configurations, and ensuring that all devices are functioning correctly. This diagnostic capability is crucial for maintaining a well-functioning network environment, particularly in homes and offices with multiple devices.

Explanation:

• upnpc: Activates the UPnP client utility.
• -s: This option denotes a request for status, prompting the utility to list details of all available UPnP devices on the network.

Example Output:

List of UPNP devices found on the network :
 desc: http://192.168.0.1:1900desc.xml
 st: urn:schemas-upnp-org:device:InternetGatewayDevice:1

Use Case 4: List Existing Redirections

Code:

upnpc -l

Motivation:

Being able to list existing port forwarding rules allows you to audit current network traffic routes and ensure that all rules are correctly set up, as well as identify any outdated or unnecessary rules. This audit can play a critical role in securing your network against misconfigurations that might expose systems to unauthorized access.

Explanation:

• upnpc: Calls the tool to perform yet another task.
• -l: This flag specifies that a list of all current port forwarding rules is required.

Example Output:

External Port    External Host    Protocol    Internal Port    Internal Host
80                        0.0.0.0                TCP               8080                  192.168.0.1

Conclusion:

upnpc is a powerful and user-friendly command-line utility that simplifies the process of configuring port forwarding rules on your router. With UPnP, tasks that typically require in-depth technical know-how and access to router configurations become easily achievable, enhancing flexibility and control over your network environment. By understanding how to use commands for adding, deleting, listing, and checking port forwarding configurations, users can better tailor their network settings to their needs, ensuring that data flows are optimized and secure.