LocalUDP

LocalUDP

Medium	Pins used	Inclusion
Ethernet port, wired or WiFi	NA	#include <PJONLocalUDP.h>

With the LocalUDP PJON strategy, multiple devices with Ethernet ports can use PJON to communicate with each other on a local subnet, wired or over WiFi or both. Take a look at the video introduction for a brief showcase of its features.

Why PJON over UDP?

If a cabled or wireless Ethernet network exists, using this to let devices communicate can be easier than to pull new wires or utilize other radio communication modules.

It can also be useful for connecting physically separate clusters of devices that are connected wired with the SoftwareBitBang strategy, or wirelessly with the Oversampling strategy, when a LAN is connecting the locations.

How to use LocalUDP

Use PJONLocalUDP to instantiate a PJON object ready to communicate using LocalUDP strategy:

  #include <PJONLocalUDP.h>

  PJONLocalUDP bus(44); // Device id 44

Set up the Ethernet card in the usual manner by calling Ethernet.begin, then call the begin method on the PJON object:

  void setup() {
    Ethernet.begin(mac, local_ip, gateway, gateway, subnet);
    bus.begin();
  }

The IP address used is irrelevant as long as it is on a subnet common with the other devices it shall communicate with. Using DHCP assigned IP addresses is fine, and the strategy does not need to relate to it. The strategy will broadcast the packets, and the correct receiver will pick them up and ACK if requested. Other devices will observe but ignore packets not meant for them.

All the other necessary information is present in the general Documentation.

Known issues

• Firewall may block LocalUDP packets, edit its configuration to allow them
• If using LocalUDP on a LAN with an attached WiFi router in access point mode, high LocalUDP traffic may lower the WiFi bandwidth because the access point sends LocalUDP broadcasts over WiFi. If this is a problem, DualUDP strategy may be a better alternative.

Safety warning

In all cases, when installing or maintaining a PJON network, extreme care must be taken to avoid any danger. When connecting a local bus to the internet using EthernetTCP or GlobalUDP all connected devices must be considered potentially compromised, potentially manipulated or remotely actuated against your will. It should be considered a good practice not to connect to the internet systems that may create a damage (fire, flood, data-leak) if hacked.