How to make a multi-player game – part 2

Hello and welcome back to my blog! This is part 2 in the series where I talk about making a multi-player game.
Last time we built a TCP socket server in node.js and we’re able to send and receive complex types. Read the first article if you’ve not already done so here.
Here is a live version of the game I’m describing in this series:

Clock synchronisation

It’s important that both the client and server’s clocks are synchronised because if there is any time based interpolation, you want both server and client to agree on what time it is and therefore at what position your interpolated object is.

Asteroids on an interpolation orbit

I use this technique in 2D Space MMO to ensure the orbiting asteroids are in the same position across all clients and on the server. The asteroids are actually interpolating on an orbit around a central location – there are no update messages getting sent to correct their positions, the only thing which keeps them synchronised is having the same time value across all clients and server.
Before we can try to synchronise clocks, we need to be sure we’re using the same concept of time on both server and client. We want to calculate the number of seconds since 1970/01/01, which is the same in both javascript and actionscript:
Read more: How to make a multi-player game – part 2