OOCSI library for Processing

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Processing Library for the OOCSI platform.

This platform can connect Windows, Mac and Linux computers (running Java and Processing), devices (Arduino, Raspberry Pi and Gadgeteer), Web brosers (via websockets) and mobile devices (iOS and Android). Please refer to the general documentation to know more about connection possibilities.


Find the latest version of the library here: oocsi.zip (988kB)

Alternatively, you can browse the source code on GitHub or clone the GitHub repository and get started with the code.


  1. Extract the zip file into the Processing libraries directory (in Windows processing-x.x.x\modes\java\libraries)
  2. Restart Processing
  3. Open the examples browser in Processing, look for the Libraries >> oocsi folder

How to use

Either use one of the examples from the Processing examples browser, or follow the short tutorial below.

Before starting with an OOCSI client running in Processing, you need to know how the OOCSI network looks like. You will need an OOCSI server running either on your computer (localhost) or available from the network. Also, any OOCSI client in the network is identified by a unique name, which serves also as an address if other clients in the OOCSI network want to messages.

Create an OOCSI client

Before you can send or receive messages, you will need to create an OOCSI client that connects to an OOCSI server (running at a specific address). When creating the client, you will need to supply also a unique name, which can be used as a handle if others want to send messages to your client.

Create a client that connects to an OOCSI server running on the local computer (running at localhost, see here):

OOCSI oocsi = new OOCSI(this, "unique name", "localhost");    

Create a client that connects to an OOCSI server running at the address oocsi.example.net:

OOCSI oocsi = new OOCSI(this, "unique name", "oocsi.example.net");

After this statement, the OOCSI client oocsi can be used in Processing code to send or subscribe for messages. Please keep an eye on the Processing console where OOCSI will print start messages and also error, in case something goes wrong.

Subscribe to OOCSI channel

OOCSI communications base on messages which are sent to channels or individual clients. For simplicity, clients are regarded as channels as well. OOCSI clients like the one created above can subscribe to channels, and from then on will receive all messages that are sent to the chosen channels. Also, clients will receive all messages that are sent to their specific channel.

oocsi.subscribe("channel red"); 

This line will subscribe the client to the channel channel red. The client will receive all messages sent to that channel. To actually receive something, the handleOOCSIEvent function has to be in place:

void handleOOCSIEvent(OOCSIEvent message) {
    // print out all values in message

In this example, all contents of a message are printed to the Processing console. These keys can be used to retrieve values from the message, for example:

void handleOOCSIEvent(OOCSIEvent message) {
    // print out the "intensity" value in the message

Instead of using "handleOOCSIEvent" as the default hub of all incoming OOCSI events, you can create a new function with the same name as the channel you would like to subscribe to, and then this function will be called for incoming evens from that channel:




void testchannel(OOCSIEvent message) {
    // print out the "intensity" value in the message from channel "testchannel"

Note that for this only channel names without punctuation and whitespace characters are possible.

Send data to OOCSI channel

Sending data to the OOCSI network, for instance, to one specific channel or client is even easier:

oocsi.channel("channel red").data("intensity", 100).send();

Essentially, sending messages follows three steps:

  1. Select a channel, for example: "channel red"
  2. Add data to the message, for example: "intensity" = 100
  3. Send the message to OOCSI

This composed message will then be send via the connected OOCSI server to the respective channel or client, in this case to "channel red".

Getting data from events

An OOCSIEvent has built-in infrastructure-level data fields such as sender, timestamp, and channel. In addition, the recipient field is provided for some client implementations. Each of these fields can be access with a dedicated getter method:

OOCSI event = ...

// sender and receiver
String sender = event.getSender();
String channel = event.getChannel();
String channel = event.getRecipient();

// time
Date timestamp = event.getTimestamp();
long unixTime = event.getTime();

Apart from that, OOCSIEvents have a data payload that is freely definable and realized as a key-value store (Map). Such key-value pairs can be accessed with helper mthods that will convert the data type of hte value accordingly:

OOCSI event = ...
String stringValue = event.getString("mykey");
Object objectValue = event.getObject("mykey");

Events do not guarantee that specific keys and values are contained. For these cases, default values can be used in the retrieval of event data. These default values (with the correct data type) are added to the retrieval call as a second parameter, and they will be assigned if (1) the key could not be found, or (2) if the value could not converted to the specified data type.

// retrieval with an additional default value
OOCSI event = ...
String stringValue = event.getString("mykey", "default");
long longValue = event.getLong("mykey", 0);
int intValue = event.getInt("mykey", 0);
boolean booleanValue = event.getInt("mykey", false);

As an alternative to using default values, one can also check whether the key is contained in the event:

OOCSI event = ...
if(event.has("mykey")) {
    // retrieve value

Finally, events can provide a list of contained keys, which can be used to dump all contained data or to systematically retrieve all data.

OOCSI event = ...
String[] keys = event.keys();

Full example

As a full example, we build a simple counter that will count from 0 up till the sketch is stopped. In the setup function, a connection to the OOCSI network is established with the handle "counterA", and after that, an initial message with counter = 0 is sent to "counterA" via the OOCSI network. In the handleOOCSIEvent function, every time a message with a counter value is received, the sketch will send it out to handle "counterA" again with the counter increased by 1. When pasting the following code into Processing and running it, the Processing console should show a fast sequence of increasing numbers.

import nl.tue.id.oocsi.*;

OOCSI oocsi;

void setup () { 
  oocsi = new OOCSI(this, "counterA", "localhost");
  oocsi.channel("counterA").data("count", 0).send();

void handleOOCSIEvent(OOCSIEvent e) {
  int count = e.getInt("count", 0);
  oocsi.channel("counterA").data("count", count + 1).send();

Other examples

The OOCSI Processing plugin comes with 3 examples that demonstrate parts of the functionality. All examples require an OOCSI server running on the same computer (running at localhost, see here). The examples are available from the Processing examples browser, or below:

  1. Client to client message sending via a direct link:

  2. Client to client message sending and receiving via a channel:

  3. Getting an updated list of all connected clients