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

Data Streams 369
Here is the full Server with some bells and whistles. A message is displayed onscreen when new clients
connect as well as when the server receives data.
19.6
Example 19-6: Multi-user server
// Import the net libraries
import processing.net.*;
// Declare a server
Server server;
PFont f;
String incomingMessage = " " ;
void setup() {
size(400,200);
// Create the Server on port 5204
server = new Server(this, 5204);
f = createFont( "Arial",20,true);
}
void draw() {
background(255);
// Display rectangle with new message color
fill(0);
textFont(f);
textAlign(CENTER);
text(incomingMessage,width/2,height/2);
// If a client is available, we will find out
// If there is no client, it will be "null"
Client client = server.available();
// We should only proceed if the client is not null
if (client ! = null) {
// Receive the message
incomingMessage = client.readStringUntil( '*');
// Print to Processing message window
println( "Client says: " + incomingMessage);
// Write message back out (note this goes to ALL clients)
server.write(incomingMessage);
}
}
// The serverEvent function is called whenever a new client connects.
void serverEvent(Server server, Client client) {
incomingMessage = " A new client has connected: " + client.ip();
println(incomingMessage);
}
Multi-User Communication, Part 2: The Client
Th e client’s job is three-fold:
1. Send mouseX and mouseY coordinates to server.
2. Retrieve messages from server.
3. Display ellipses in the window based on server messages.
All messages received from
one client are immediately
relayed back out to all
clients with write().