Learning Processing: A Beginner's Guide to Programming Images ...

Here is the entire client sketch:
19.7
Example 19-7: Client for multi-user whiteboard
// Import the net libraries
import processing.net.*;
// Declare a client
Client client;
void setup() {
size(200,200);
// Create the Client
client = new Client(this, "127.0.0.1", 5204);
background(255);
smooth();
}
void draw() {
// If there is information available to read from the Server
if (client.available() > 0) {
// Read message as a String, all messages end with an asterisk
String in = client.readStringUntil( '*');
// Print message received
println( "Receiving: " + in);
// Split up the String into an array of integers
int[] vals = int(splitTokens(in, ",*"));
// Render an ellipse based on those values
fill(0,100);
noStroke();
ellipse(vals[0],vals[1],16,16);
}
}
Data Streams 371
// Send data whenever the user drags the mouse
void mouseDragged() {
// Put the String together with our protocol: mouseX comma mouseY asterisk
String out = mouseX + " ," + mouseY + " *";
// Send the String to the server
}
client.write(out);
// Print a message indicating we have sent data
println("Sending: " + out);
Multi-User Communication, Part 3: All Together Now
When running a multi-user application, the order in which the elements are launched is important. Th e
client sketches will fail unless the server sketch is already running.
You should fi rst (a) identify the IP address of the server, (b) choose a port and add it to the server’s code,
and (c) run the server.
Afterward, you can launch the clients with the correct IP address and port.
The client reads messages from
the Server and parses them with
splitTokens() according to our
protocol.
A message is sent whenever the
mouse is dragged. Note that a client
will receive its own messages!
Nothing is drawn here!