ardupilot/Tools/UDP_Proxy

UDP Proxy

This is a tool to do UDP proxying, particularly for MAVLink connections. It is useful when operating both a ground station and aircraft on network links that don't have a public IP address.

Functionality

udpproxy opens two listening UDP ports. When it has a connection on both ports then it will forward packets between the ports. This allows your GCS to connect to one of the ports and your aircraft to connect to the other port. The GCS and aircraft will be able to communicate, despite both not having public IP addresses.

Why not a VPN?

udpproxy is an alternative to using a VPN for communication between the aircraft and the GCS. The reason for not using a VPN in flight is VPNs typically have a high reconnect time, and often add significant latency. This poses an issue for aircraft control as you may lose the ability to control the aircraft for minutes if there is a short network outage. Using udpproxy minimises the time for the link to re-establish after a network outage.

Disadvantages

The main disadvantage of udpproxy is that it offers no security. If someone knows that UDP ports and host you are using then they could connect to your aircraft and control it. The risk can be reduced by enabling MAVLink2 signing which allows you to ensure that nobody can control the aircraft without knowing the signing key.

You can also reduce the risk by using firewall rules on the computer to run the proxy on to only allow connections from the IP ranges you known you will be using.

Building

Just run 'make' command

Usage

Basic usage is:

udpproxy PORT1 PORT2

this will listen on both PORT1 and PORT2. You should then make an outgoing UDP connection from both GCS and aircraft to those ports, one to each port.

Adding the -v option tells udpproxy to display information about new connections and shows transfer rates which are useful for diagnostics.

You should run udpproxy on a computer with a public IP address.

Keeping it running

You will typically want to keep udpproxy running for long periods without having to keep a shell open on the computer running the proxy. An example script which starts it under GNU screen and thus allows you to monitor the connections and automatically restart them is provided in this directory.

Connecting

To connect from mavproxy to your proxy just add this to the mavproxy.py command line:

--out AA.BB.CC.DD:PORT1

where AA.BB.CC.DD is the IPv4 network address of your proxy.

To connect from MissionPlanner use the "UDPCL" option, and enter the IP address and port number of the proxy.