This example is not standalone client code and includes an ad-hoc server.

To try it, run the server, on the port 1234:
  ./server 1234
Then point two browsers to:
  http://localhost:1234/index.html

Then draw in one instance of the client to see your drawings appear
"simultaneaously" on the second (the drawing commands are sent at
regular time intervals inducing a lag between drawing flushes).
