The drawing is basically a list of strokes, and a stroke is a list of points - that is, (x, y) coordinates. So the database is mostly a huge table of (x,y) coordinates.
Uploading the entire canvas would far too inefficient - I simply upload the points.
The transfer between two clients uses a technique called 'long polling'. That is, the client sends an HTTP request to the server, and the server doesn't respond until it has received a message (ie. stroke) from another client.
Uploading the entire canvas would far too inefficient - I simply upload the points.
The transfer between two clients uses a technique called 'long polling'. That is, the client sends an HTTP request to the server, and the server doesn't respond until it has received a message (ie. stroke) from another client.