Allowing trading and exchanging items with other players provides a lot of possibilities for game play in the virtual world. For example, players can work as a group to collect different items for the same collection. Or they can focus on finding specific elements and collect them to mix some high-level items. However, allowing trading between players may also cause some problems. It is difficult to totally prevent players from paying real money for virtual items. If the design of the virtual world does not allow trading with real money, the virtual world designers have to think carefully on the trading mechanism to prevent it.
Trading items with other players requires a complex data flow between two clients. We will further discuss the implementation methods in the next chapter, which will focus on the communication between players.